MG Midget and Sprite Technical engine breather BBS discussion at MG-Cars.net

MG Midget and Sprite Technical - engine breather

After starting from cold after about mile or so my Frog blows a big cloud of blue smoke from the exhaust it clears and is not repeated. Oil consumption is minimal(1500 per pint). Engine is a 1293 Cooper 'S' spec with sealed breather system. New Slark head recently fitted made no difference. All compressions within a couple of PSI. Thoughts? Bob

Bob Beaumont

Often down to oil going down the valves which have no top hat oil seal. Putting them on all 8 will usually fix it.

F Pollock

Yes I suspect a Slark head would not come with a full compliment of seals?

Bob Turbo Midget England

Slarky did put on the seals as I was there when the head was assembled . Also if the seals were suspect would the problem also occur when hot? It does not do it on initial start up only after about 5 mins running and then afterwards there is no smoke. Anything to do with the breather system??

Bob Beaumont

Thoughts...? Don't worry about it...

James Bilsland

No seals on the exhaust. No problem. Live with it as "fixing" it is more trouble than it's worth

Onno K

A tentative suggestion - maybe the rubber hoses for your sealed breather system have become partially gunged* up inside, so that they initially build up pressure after a cold start, and then as it warms this lets go a fart* of oil into the engine until it is breathing clear again? * technical terms

Guy

I like the 'fart' idea and will check the hoses.

Bob Beaumont

What do you mean by a sealed breather system? I had exactly the symptoms you describe, and never resolved it. On mine -- (a 1275+30thou engine, 1300GT big valve head, and 19320 cooper S pistons), -- exactly as you describe, after about a mile or equivalent amount of time for initial warming, the breather system sucked oil up the timing chain cover, and stuffed it in the inlet manifold. Result, big cloud of blue smoke. I used to let the revs die to tickover, or stop momentarily, and thereafter it was fine until the next time I started from dead cold. It was always worse in the winter, or very early in the morning on chilly summer mornings. That engine is now my spare, awaiting strip and rebuild. I suspect my front cam bearing alignment, allowing too much oil into the timing cover, along with possibly a partially restricted oil return drain hole in the bottom of the timing chain area. One other suspect is piston blowby, until the engine was hot enough to seal the rings in the bores. My breather was, and still is, the timing cover to y-piece, to inlet manifold, with vented filler cap in rocker cover. I don't have the problem in my current engine, with a very similar spec.

Lawrence Slater

PS to my previous post. The engine did well in excess of 100thou miles before I swapped it out, and apart from the oil problem when just warming up, it went extremely well indeed. The heads off now, and the bores look very good, with a small wear lip.

Lawrence Slater

This happened on my old 1275 around 110K miles. I rebuilt/re-bored the engine and it never happened again. The only defect I found (if you ignore worn rings) was a broken ring. I concluded that braking downhill may have forced oil onto the (front?) bore that couldn't be cleared by the rings. Once the oil became hot, it scraped down the bore more easily. A

Anthony Cutler

Lawrence, The symptoms as you describe are identical! I have the same breather system.The engine has only covered about 20K miles since its original rebuild (although that was 15 years ago)which was a rebore but I don't recall the cam bearings were changed.The spec of the engine is identical to yours. Sounds like I will just live with it!

Bob Beaumont

I think what happens is that when you stop the engine and let it cool overnight, warm oil vapour in the breather pipes condenses and solidifies into an oily/ greasy lining to the pipe. On restarting from cold, this semi-solidified gunge sits there fore a while but as the engine warms, the crankcase vapour being pulled through the pipe warms the pipe to a point at which some of the oil gunge liquefies and lets go, releasing a dollop of oil/grease into the induction manifold. Once it has warmed up enough to cough out this phlegm it then runs clear until the next cooling cycle. This would explain why it doesn't happen immediately on start up, as the pipe, being external to the engine, remains cool for some while after starting. Cleaning the pipe, or perhaps better renewing it should solve the problem.

Guy

I like that logic Guy it sounds reasonable to me and I would go with that until someone totally disproved it. Hope Bob gives it a try and reports back? I had a Montego turbo that had similar problems but that was cured by cleaning out a similar style filter/seperator. By the way I like your terminology and the word ""phlegm"", kind of reminds me of the Python sketch about what would be a good word for Belgiums and the winner on the spoof TV program was what is wrong with simply calling them "Flems" or was that "phlegms"?? Sorry to our Flemmish European friends for any offence caused.

Bob Turbo Midget England

Guy's thoughts sound good to me. I would add a catch tank in the breather circuit before the Y piece, that should allow the oil to settle out of the crankcase fumes but not effect the functioning otherwise.

David Billington

I would have gone along with that too Guy, and I don't say it doesn't happen to some extent, in fact I've seen it. However, in order to try and work out what was actually happening in my engine, I fitted a transparent thick wall plastic pipe, from the timing cover breather to the y-piece. I was able to observe a thick column of engine oil being sucked up the clear pipe and dumped into the manifold. Anthony. I didn't mention it, as I thought I might be imagining it, but I did think it was worse, when the engine was at "the right temprature", and I was braking reasonably hard. And this sounds daft, going down hill. Now you've said you experienced the same under braking, I know it was the case. So the oil in the sump, must surge forward, and somehow too much of it ends up in the timing cover. From there, it is sucked under vacuum (the vacuum would increase as the oil would fill the cover and pipe), into the inlet manifold. My assumption, is that this might be aided by excess sump pressure, caused by blowby in one or more of my bores. And as said, I also suspected the front cam bearing alignment. However, if Bob B, is getting this without the cam bearings being changed, then perhaps they are innocent. When the oil reaches a sufficiently warm temprature, the problem ceases. I always assumed this was because the thinner oil would drain back into the sump via the bottom of the timing chain chamber, faster than the pipe could suck it up. Plus also, as Anthony says, when the engine reached normal temp, the rings sealed the bores, and sump pressure was reduced to normal. I have some additional thoughts on this. The bigger inlet valves in the 1300GT head, give a greater suck on the breather. My current engine runs a Peter Burgess fast road head, with the same size valves as the 1300GT. When I first started this engine up, after a quick temporary rebuild using Cords rings, I had the same sucked up oil symptoms. Sure enough, the clear plastic pipe confirmed it. At the time I had twin HS2's on it. I then changed to a single HIF44, and the problem has never come back. I've speculated that the degree of depression at the breather connection point on the HIF44, is less than that at the 2 combined Y-piece connections on the HS2's. Also of course, the cords have since done their job, and the rings are no doubt well and truly bedded in. PS. I also tried a catch tank, but the volume of oil was sufficient to fill it, as it did the seperator on the timing cover.

Lawrence Slater

Thanks for all the useful comments. I will replace the pipe from the timing cover to the carbs and see what happens. I always know when its going to 'Burp' as the engine misfires slightly and out hey presto a big cloud of blue smoke. Interesting last summer I drove to Angouleme to watch the racing and the weather was warm all the time and there wasn't any problem. It sort of adds validity to Guy's comment about condensing oil/grease. I have always run a big valve head, the new Slark one being an unleaded version of the old one so Lawrence's point about extra draw on the breather may be quite relevant. I did own a 1300GT in a past life with the same breather system and it was fine however....!

Bob Beaumont

Interesting that Bob's Montego Turbo did it too. So did my mad car MG Maestro Turbo! There's a car I should have kept - they are quite collectors items now I gather. Obviously it is something in the genes!

Guy

My Maestro 1.3 wasn't very quick LOL, but it never ever let me down. Same with my 1.3 Maestro van, but that eventually died of tin worm. Those turbos were quicker to 100mph than contemporary Ferraris I hear tell. Bernie.

b higginson

No comment then, that I observed on numerous occasions, a solid column of oil being sucked up the transparent breather pipe? And that cleaning and replacing the pipe made no difference? Bob, try fitting a clear plastic thick wall pipe, so you can better see what happens. (You need thick wall to stop it collapsing when it gets warm). I hope just cleaning yours does the trick. :) Also your comment about driving in warm france, without the symptoms, confirms my view about it happening only in colder temps. I drove all over greece spain france without issue too.

Lawrence Slater

ps. Ran out of edit time. Wish they'd make it 10 mins :) It wasn't just condensation, there was too much oil dumped in the inlet for that. I remember taking the air filters off to take a look as soon as it happened, and there was a copious amount of engine oil behind the butterflies. Yours may be different to mine, in that others seem to be describing a puff of blue smoke that may well be due to residue in the pipe caused by condensation. I am describing, as I thought you were, a thick cloud of blue smoke, and oil residue on the tail pipe until it burned off. I also remember sudden pinking, and taking the plugs out as soon as it happened, and getting wet oil from the plugs. Definitely not just condensation.

Lawrence Slater

Lawrence, There wasn't really anything to question or doubt about your theory. Your descriptions sounds plausible although I didn't quite follow what it was that caused the delay before the "gulp". Is it just a matter of the time driven before the first steep downhill or firm deceleration? If that is the case, presumably one could initiate a blue cloud at will during the first 5 miles or so of driving, which would be a good test of the theory.

Guy

Yes it was a common problem with the O series Turbos (MG Maestros and Montegos) when the inline filters became blocked with sludge. As said the MG turbos were extremely quick and were I believe the fastest saloon cars on the market at the time. Not sure why the O Series Turbo engine has never been a common swap into an MGB, certainly one I have considered doing for a long time.

Robert (Bob) Midget Turbo

Bob - mostly due to the shortage of Sherpa gearboxes...

David Smith

Guy, I can only call it the goldilocks condition. When circumstances were just right, it would happen, and not at other times. After starting from dead cold, at the right temperature/ oil viscosity, perhaps in combination with extra sump pressure caused by blowby, perhaps combined with braking that caused the oil to surge forward and enter the timing chain chamber in a greater quantity, --- at the point, the oil would get sucked up out of the timing cover, and enter the manifold. I found that if I kept driving the oil would keep getting sucked up, until the engine was much nearer to normal, or hot, when it would cease to suck oil. But if I stopped and let the engine tickover for a few seconds, or stopped altogether, then when I started up again, it didn't happen. This is what I know is certain, -- I think. :) For the oil to be sucked up out of the timing cover in a solid column, there must be an excess amount of oil inside the cover, enough to reach the internal opening of the oil seperator. What I don't know is how it got there in excess quantity, and why it didn't drain away sufficiently to prevent filling the timing chain cover. -- Maybe the drain was blocked, but that doesn't explain why it only happens from dead cold start, and why once hot the problem ceased. --- Unless the drain was partially blocked, and would only allow hotter, thinner oil to drain away. I definitely remember occasions when not long after starting, and then braking hard, it would coincide with the problem. However, it would also happen on occassion, on a flat road, and not under braking. I did try to make it happen, but as I said I thought at the time it might have been coincidence/imagination. Anthony mentioning it reminded me, and prompted me to think it might actually be a contributory factor. But if not braking was the primary cause, that's why I thought of my front cam bearing, perhaps sending too much oil into the timing chain cover, but again only when the temperature conditions were just right, after cold start. Somehow, when the temp is just right, too much oil gets into the timing cover to be able drain away, and up it goes into the inlet manifold. I never found out what why and how. And note, the sump wasn't over filled, and the dip stick was indicating the correct level. Those were the first things I checked. I posted this problem here many years ago, about 10/11/12 or more in fact, and nobody had an answer then either. I could probably find the thread in the archives. So if Bob B, now has the same issue, I might finally get an answer myself. :) If anyone can work it out.

Lawrence Slater

My symptons are identical to those descrbed by Laurence. The engine misfires/ pinks, big cloud of smoke which takes a time to burn off in the exhaust system. It is not just a 'puff' I have obtained a new pipe and ordered a replacement filler cap as a further precaution although the existing seems ok,it is several years old!. Over the weekend I ran the engine initially for 15mins to warm it up, then did about 20 mins driving which included some enthusiastic braking downhill. No blue smoke. I did remove the pipe from the Y piece and there was little evidence of oil and there was nothing in the butterflies. I agree there appears to no consistent scenario for when this problem occurs. It tends to happen on colder days but there is no guarantee it will. Driving style also makes no obvious difference, I have equally tried gentle driving changing up early to more aggressive leaving it the gears and flooring it and still the problem happens. I'll report back if the new bits make any difference.

Bob Beaumont

Bob, I can unfortunately, pretty well confidently predict, that the new bits you mention won't fix it. I Hope I'm wrong, and I could be, but if you have the problem I have, ---------. I tried several different filler caps. I tried blocking the filler cap, and I tried removing the wire in the filler cap. -------- No change. I took off my timing cover, and soaked it in petrol to clean it, and then I got a spare from which I removed the wire. ----------No change. I pushed a smaller tube inside the breather pipe from the timing cover, and then a smaller one still. -------No change, until I effectively, eventually, blocked the pipe because the remaining bore was so small, and of course that "fixed it". I.e, no sump breather. No solution. I pulled and stripped the engine, and the only thing I could see that might be odd, was that my front cam bearing is not lined up with the front of the block. This led me to suspect that too much oil was being delivered to the timing cover. I went back to the engineering shop that fitted the cam bearings, and he assured me the cam bearing could only go in like that. A good place in Battersea with a long reputation. So I had to accept that. I rebuilt the engine, and lived with the problem for years, until it was well into the hundred thou + mile mark, and I swapped it for my spare engine. -- My current engine. I'm still suspicious of the front cam bearing, but another engine shop recently told me the same thing, and you or course haven't changed your cam bearings, which further reduces the likelihood of the front cam bearing being the cause.-- --Unless you don't know the history of your engine, and maybe the cam bearings have been changed in the past? You're the first person other than myself, that I have heard of having this problem. Where there are two, there must be more. So now I'm really intrigued. One of the reasons my spare engine, is still my spare, is because I haven't got the motivation to rebuild it, only for the same thing to happen again. If I don't know what causes the problem, I am unlikely to fix it. Bob, what do you know about the history of your engine? For both of us to have the same problem, which seems to be pretty rare, there must be a common denominator. You mention CooperS spec. What piston do you have? I ask because the problem started for me, 25 plus years ago, when I had the engine bored to +30 and fitted 19320 pistons. At the same time, I also had new cam bearings, and installed a Piper285(or was it a 270?)cam. ----- Anyway, as soon as I started the engine, and drove it, within minutes, I sucked up oil. I stripped the engine, and put back a standard cam. I thought that improved it a little. Probably not, but maybe. Anyway, as mentioned the engine shop reassured me about the cam bearings, and that left the Pistons. Maybe for some reason they are wrong in some way. I'm guessing. I had good compression, and the engine went smoothly, and bloody well. -- Except all too often, when first started from dead cold, on chilly or cold days. But something very logical is happening to make the timing cover fill with so much oil, that it gets sucked into the inlet. Either it's too much pressure in the sump, or too much suction. But for some reason the timing cover fills with oil, and up it goes. I obviously didn't think logically enough about it back then, but I'm sure there must be a way to isolate the cause. As your engine is running, --- if it bothers you :) --- then you might be able to work it out. But it's a difficult one, becuase you need Goldilocks to be there at the time. So come on you eggheads out there. Does anyone have an answer to why this happens? :)

Lawrence Slater

1)The case for too much suction. When the ambient temp is low enough, and the engine is cold, or just above cold as seems to be the case, and consequently the oil is thick enough, -- the oil will take longer to drain back to the sump from the timing cover. If at that time, more oil enters the timing cover, than is draining back to the sump, then, if the suction is strong enough, the oil will be sucked into the oil separator, sufficient to fill it, and then be sucked into the manifold. Could the combination of the increased inlet valve size, combined with cooperS pistons, create a suction greater than the original specified, sufficient to suck up the oil in the first period of warm up? Seems unlikely, as I very much doubt that either mine or Bobs engine is unique in having these engine specs, and nobody else has reported this problem. However, I mentioned before, that when I first started up my current engine, with similar specs to my spare engine, I had the same problem. I then changed the twin HS2 carbs to a single HIF44. The problem went away and has never returned. Is the suction at the point of connection for the HIF44, less than that of the twin HS2s? 2)The case for too much sump pressure. When the ambient temp is low enough, and the engine is cold, or just above cold as seems to be the case, there is inadequate ring sealing in one or more of the bores, and excess sump pressure develops. This somehow forces oil into the timing cover sufficient to fill it. The oil is still thick enough not to drain away fast enough, and the suction from the inlet manifold sucks oil into the engine. Also seems unlikely, since I would certainly have noticed a poorer performance from cold, if the rings were leaking to that extent. I would have recorded low compression, and would have found oil being pushed out of the dip stick, or at least felt pressure there. I didn't. 3)The case for oil surging forward. When the ambient temp is low enough, and the engine is cold, or just above cold as seems to be the case, braking and or going down hill, causes the still thick oil to surge into the timing cover ---- possibly through the timing cover drain holes----. The suction grabs the oil, as it is of course unable to drain away. Seems unlikely on it's own, as everybody would have this problem if that was the case. I think that maybe this exacerbates the problem, in combination with one or both of the above. Problem. How to set up an experiment, that will isolate the cause of oil being sucked into the inlet manifold, when the ambient temperature has to be just right. As spring and summer approach, the window of opportunity is closing.

Lawrence Slater

Lawrence, The reason I suggested the oil condensation in the pipe theory is because I used to get a puff of smoke from my engine, maybe 5 minutes into driving, and then when accelerating briskly. It was a brief puff, but very blue and sufficient to catch my eye in the rear view mirror as I accelerated. It was so regular that I learnt to expect it on a particular bit of road, accelarating uphill away from a roundabout. I got rid of the problem by fitting new pipes. BUT, that is not to say that similar symptoms are not caused by more than one set of circumstances. So your oil drainage issue sounds like it could well be the cause in this case too. But it does seem surprising/ unlikely if this is a design fault that it hasn't been picked up on over the last half century. So that would leave either an assembly fault - as perhaps you suspect with that front cam bearing alignment. Or it is an occasional manufacture fault such as a restricted oil return pathway. On this, I remember questions on here a year or two ago about the rather rough and irregular "window" in the front of the block casting. There were photos posted of what appeared to be an incompletely knocked out web of casting on the front of the block. But I don't know, is this the oil return hole? And maybe if it is then it is supposed to be knocked out and cleaned up during manufacture - and maybe yours (and Bob's) isn't? It is clearly a very specific combination of circumstance, probably including oil level, viscosity and temperature plus engine revs (suction) G forces and the physical features of the engine. Very complex!

Guy

Hi Guy, I don't disagree with you about the condensation issue, it's probably there too. But this is different -- additional?. The more I've been thinking about this, as I've been writing, the more I remember. When it happens the whole sound of the engine/exhaust note changes. It really does sound like it is pumping liquid oil through the exhaust, and if I used to allow it to continue long enough, it would drip from the tail pipe. I'm sure you've followed cars and bikes in the past, when the engine was so knackered, that truly thick clouds of blue smoke was being emmited from the exhaust. So thick you could taste it. That is the effect of this too. It's as if you took the plugs out, filled the chambers with engine oil, and managed to start the engine. As I have my spare engine ready to strip, when I do, I will take pics. I didn't take many pics last time 25 years or so ago, other than the cam bearings in situ, that I posted here in the middle of last year. You may not have read that thread. Anyway I'll take a good look at the drain holes or whatever it is. I'll look for the rough casting you mention. I seem to think, that drainage is only via 2 drillings in the front main cap, but I might be wrong about that, as it's been a while since I last stripped one. That's also a point about oil level, but again, I was pretty certain I hadn't over filled (even though I'm not too sure about my dipstick -- see other thread Keith has posted dipstick measurements ---- ). Also, I'm willing to stake my life that others have put in excess engine oil, and it would certainly have become common knowledge, if it led to pumping oil out of the exhaust. It's a puzzler aint it. :)

Lawrence Slater

Yes Lawrence, I was agreeing with your possible diagnosis - this time anyway! It is just odd that it doesn't seem to happen more often, unless there is a specific fault which only occurs to a small proportion of these engines. But maybe the fault itself is more commonplace, but it needs to be combined with the particular other factors all at the same time for it to manifest itself. Maybe its related to the phases of the moon as well! Like a spring tide perhaps.

Guy

Well, back in my youth, I used to do a pretty good wearwolf impression, but never whilst driving in a full moon. lol. Seriously? Extra gravitational pull? :) Frankly, I had given up looking for a solution, and had concluded, that as nobody had ever even heard of the problem before, let alone experienced it, I was either mad, or was doing something really stupid, that I just couldn't see. So in that sense, I'm truly grateful to Bob B, for exonerating me, and returning my sanity. :) But now, I'm all fired up again, and determined to find out the cause. As for agreeing with me, this time, when did you last disagree with me? :)

Lawrence Slater

It was just a comment to reassure you that agreeing this time wouldn't set a precedent. :-) Moon gravitational effect wasn't being serious, although it is a pretty powerful effect to be able to change sea level by up to 10 metres so maybe there is some truth in it!

Guy

Lawrence I am glad i have returned your sanity! One good thing at least! The engine I have is a very early 1275 number 12CC 1084!It came out of a written off MKiv Sprite which had only done a few thousand miles.Its bored +20 and has forged ST 'S' pistons, steel crank which has not been ground etc. Standard cam, I have had it for many years and it used to be my sprint engine. It originally ran with a 649 and a Longman inclined valve head matched to a 45DCOE. All great fun. However I wanted to go racing and did not want to hack about or risk damage to my all steel frog so I aquired a modsport frog. I detuned the engine by refitting a 1300gt head, road cam and twin SU's.It uses an ST exhaust manifold and ST silencer. In sprint form I never had a problem, it was only when I fitted the SU's the problem started to become evident. I only used the closed breather system as the new SU's had the take off for the Y piece! I don't know if any of this helps and perhaps its just one of those things. At least there is two of us working on a possible reason now!

Bob Beaumont

Bob, "In sprint form I never had a problem, it was only when I fitted the SU's the problem started to become evident. I only used the closed breather system as the new SU's had the take off for the Y piece" This sounds to be the reverse of my current engine, when I initally had the problem, but it went away, when I converted to a single HIF44. On my spare engine, the one I first noticed the problem, I had twin HS2s, the 1300GT head, and S pistons at 30+. Is this relevant, or just circumstantial? Do the two HS2s setup result in a greater suck than a single HIF44. As you weren't using the closed breather prior to the conversion to HS2, the problem could have been there waiting to happen. So is there a common factor?

Lawrence Slater

It occurs that the amount of "suction" at the carbs is greatest when the throttle is closed. But should in theory be dependant on the efficiency of the engine breathing downstream of the throttle disk. The size of the carb upstream of the disk should be irrelevant. But if it sucks in oil on the overrun it would then burn and belch out blue smoke if you then immediately accelerate again. Kind of fits with your earlier comment about sometimes occurring immediately after braking.

Guy

Yes, exactly Guy. Not having the problem and relying on years old memories, I had forgotten that bit. Overrun seemed to initiate it, which you would of course likely be doing when braking, and or going down hill. I remember now, trying to "feather" the acceleration, to avoid burning oil, not thinking that the overrun, high vacuum, had already filled the bores with oil. Hmmm. The suction, greater or smaller, is there all the time on this kind of system. So isn't directly the cause, although more vacuum, might well make it worse. The root cause must be excess oil in the timing chamber, because, either too much is being delivered there, or it can't drain away fast enough. But it only happens at that goldilocks temprature, when the oil is at the right viscosity. The timing cover is fed with oil, to lube the chain and sprockets. There must be a decent amount, in order to necessitate the oil seal on the crank nose. But not so much, that the level increases to the point that it covers the internal opening of the oil separator/breather. Which it must be doing in order for it to then be sucked into the inlet manifold. So the questions are, how is the oil delivered to the insides of the timing cover, and how is it supposed to drain?

Lawrence Slater

time for a daft question your dissy is without vacuum advance? and I know you weren't meaning that

Nigel Atkins

I've got a 25D4. It doesn't seem to suffer from too much vacuum advance if that's what your thinking? And not daft, anything is worth considering, within reason. :)

Lawrence Slater

obviously you need to check the vacuum is working properly but you could try disconnecting and blocking the vacuum off both ends and see if that makes any difference to the oil problem - I know it shouldn't but . . . or it might point you towards something else I remember reading somewhere that even after as little as a couple of years from new the dissys weren't working that well

Nigel Atkins

Nah Nigel, now you've gone off at a tangent. :) This has nothing to do with the vacuum advance on the distributor. And thinking about it, the vacuum take off provided for the distributor, is not the same as for the breather. The distributor function has nothing to do with the breather system, as it pertains to the timing cover, if you get my meaning. Nigel, in your collection of records and books, do you have anything that talks specifically, about the oil feed and drain to the timing chain? How is it fed, and how is it drained? My memory says it is fed via the front cam bearing, and drained via 2 drillings in the front main journal cap. Do you know if that's correct?

Lawrence Slater

yes I know it's not the same but I wondered if there was a stutter in the dissy mech from your pedal actions which may not be noticed, do you remember whatsit Burke's programs about one thing seemingly unrelated leading to another, I'm sure computer programers would have a term for it as they're doing it all the time I can assure you sometimes even the experts say try it and see because even they don't know because of all the possible permutations let alone how one worn part or component acts on or reacts to another worn, or new, or anywhere in between, part or component now you know if it's technical I won't know where to find it even if I had it, I only have two Haynes, neither of which cover my car year well and the factory workshop manual on the not so convenient DVD, sorry there was a thread on it here a while back

Nigel Atkins

I found this BMC A-Series engine lubrication Steve Maas Long Beach, California, USA July, 2007 "9. The timing gears and chain are similarly lubricated by splash lubrication. Oil passes through a hole in the front of the block, between the camshaft and main bearings. " At. http://www.nonlintec.com/sprite/lubrication/ I hope you won't mind Steve if I reproduce a segment here. :) Significantly, the fron cam bearing is flush with the center of the block face. Mine is recessed quite a large amount. This is what led me to specualte about oil coming from the cam bearing, in excess quantities, and filling (partially anyway) the timing cover. It doesn't say how it drain here.

Lawrence Slater

Here's my front cam bearing picture, taken 25+ years ago. OK, not as much as I remembered. It is recessed, but if weren't it wouldn't line up on the oil feed to the head. Have I got a wrong front cam bearing fitted? How much oil I wonder could be spilling out from the cam journal? Edit Actually I have that wrong, if the bearing is moved forwards it would block off the feed to the camshaft journal. But looking at, it does appear that a decent amount can spill out into the timing cover.

Lawrence Slater

Lawrence, Vizard has a bit about lubrication with diagrams that confirm the arrangement in the photos you just posted - page 400 in my copy (2nd edition, 1989 reprint) In your first photo, the raggedy hole that I was talking of is labled "hole to block interior" I think this is where much of the "splash lubrication" comes from. Does (or did) you engine have a particularly high oil pressure? Very high oil pressure might result in faster oil flow out of the front cam bearing. So. I imagine would any restriction on the onwards gallery to the head. I don't see why your front cam bearing being slightly deeper set into the block should increase leakage here. Presumably contact surface with the cam itself isn't reduced, it just runs slightly further back on the camshaft? Still not obvious from those photos how oil is returned to the main sump?

Guy

Guy, I always did have very good oil pressure, and in fact my current engine, reaches at least 80psi on startup -- but doesn't have the oil problem--. -- I suspect I have a partial blockage in the bypass, as I have checked the pressure relief several times. If the cam journal isn't wholly covered by the bearing, don't you think it possible for an amount of oil to escape in the forward direction? The rear of the front journal would be completely covered, but the front exposed to free air. I'm guessing I admit. Yes agreed, what's needed now is a picture of the front engine, without the front plate and gears, and with the crak in place. Is anyone out there at that stage of an A series, particularly a 1275, rebuild?

Lawrence Slater

Yes, I can see that if the cam bearing is recessed, then there may be a bit of the machined journal exposed at the front, (and rather less exposed at the rear. But surely the rate of "leakage" depends on the oil pressure, viscosity and the surface over which it flows. The latter isn't altered just because the cam bearing sits slightly further forward or back on the cam journal. Assuming that the surfaced journal is wider than the cam bearing. If the width of the journal were less than the cam bearing, then it would leak more oil if the cam bearing was too far forward, creating an "overhang" with the end of the cam journal. I think we, or rather I, am out of my depth with this. Need Peter Burgess or an race engine builder to wade in here with some proper knowledge!

Guy

Yep, agreed, ---- Help! But you mentioned viscosity. When the goldilocks moment strikes, at the perfect viscosity, could it be, that the exposed journal allows for just enough oil to escape at that point, -- he asks, clutching at any straw handy to save a raipdly dwindling theory?

Lawrence Slater

I think my front cam bearing theory is gaining legs again. Haynes confirms my thoughts that the cam front bearing does deliver oil to the timing cover. Haynes says that the camshaft end float should be measured to be within tolerance. What if, there is excessive wear in the end float? Wouldn't that, as the oil begins to thin, but still at coldish pressure, allow more oil than desired to reach the timing cover? The oil couldn't drain away fast enough, because it is still too viscous, and the only drain holes are as shown in the picture of the front main cap --- also haynes. I admit to reusing my cam cover plate, I don't recall ever replacing it, as it looked ok to me and I was tight. :) My spare engine has been rebuilt by me twice. Maybe before that too, by a previous owner. So, along with the splash feed oil hole in the front of the block, oil is delivered to the timing cover via the small hole in the cam cover plate. This small hole is supposed to regulate the amount delivered. But because the end float is too great, at just the right temperature, as the oil thins, more oil than intended is allowed to pass. Excess oil enters the timing cover, and can't drain away yet, because it's still too thick. As the engines warms, the oil thins further, pressure drops a little, and the thinner oil drains at an equal or greater rate than it enters the timing cover, and the engine stops sucking oil. Howzat?

Lawrence Slater

There are oil drain holes in the front main bearing cap. The timing gear case isn't pressure fed - a small amount of oil finds its way through past the cam and timing gears and is thrown around the chain by the 'F for flinger' (Oil thrower ring). I've never stripped an engine and found excessive quantities of oil in the timing case (it would pool in the breather canister if the case was overfilling) Oil coming through the breather is likely to be condensed oil mist forced out by positive crankcase pressure, or sucked out by negative manifold pressure. My solution on a race engine would be 1) increase breathing capacity on the engine 2) isolate the feed into the carbs (ie feed it into an oil catch tank) and block the carb take offs However I don't think its such a big deal on a road engine particularly in Bob's case where the oil useage is fairly minimal - although if you dislike the occasional puff of blue smoke I would adopt the above solution. Regards JB

James B

Very good Lawrence. Very clear. If you look at my responses, I have acknowledged throughout that your theory could well be correct. I am not particularly convinced about the camshaft position / end float being an absolutely necessary part of the equation. It may just be that the cold viscous oil is actively pumped in, but is limited to passive flow to run out of the chaincase. All that would be required is a combination of a high oil pressure and a reasonably free-flowing delivery from the front cam bearing. Oh, and high suction from the carbs. James, I do not like your option 2 - at least not the blocking of the carb connections. Suction through the system is essential to give any hope at all of limiting oil loss from the rear crankshaft scroll. Add a catch tank by all means, but it needs to be drawn through by use of carb manifold suction.

Guy

James, with respect, you've missed the points. 1). It's not a common occurence, so you may never have come across it. And by the time you strip an engine, the oil has drained anyway. 2). It is not a small puff of smoke, it's a cloud like a bonfire, and it could go on for a minute if you let it. 3) Isn't oil delivered, albeit at a reduced pressure, to the cam bearing and hence at some pressure at least through the hole in the cam cover? 4) This is not condensed oil vapour. If you read my earlier post, I have proved it to be a solid column of liquid oil. I fitted a clear plastic breather pipe, and observed the oil rise up the pipe in an unbroken column. There is no doubt at all that the breather canister fills completely with oil, and when it does it is sucked up into the manifold. However unlikely this sounds, that is what is happening. I just don't know why.

Lawrence Slater

I would still be looking at positive crankcase pressure as opposed to too much oil pressure/overfeed to the timing chain case. For what its worth race engines don't run manifold breathers because of the octane reduction issue and because DCOE's don't come with a take off - I find that if you fit sufficient breathers and fit the oil scroll correctly they also don't tend to pump all their oil out the rear main.

James B

Thanks Guy, but actually I still don't like it. I just can't think of what other way, so much oil gets into the seperator, and gets sucked into the engine. If Bob hadn't started this thread, I wouldn't have raised it again, as I wasn't believed the last time I did, more than 12 years ago on this very site, back when it was only general and not technical. But having someone else with the same experience, has made me want a solution.

Lawrence Slater

James, sump pressure is one consideration on the table. But if it were that great, wouldn't that reveal itself at for example the dip stick, and by positive pressure at the rocker cover filler cap? And how would that pressure get behind/under the oil, to "push" it into the timing cover? but I think you may be right. If I can't find out why, if when I rebuild my spare engine it happens again, I have to try the solutions you mention. For now though I want to know why.

Lawrence Slater

Sorry James, I am aware that you build race cars. I should have added that my comment was meant to apply to road cars only when the effect on octane level is less significant. I have a catch tank, but I have it plumbed through to the carb manifold and it works well. But then this engine doesn't suffer Lawrence's oil gulp problem!

Guy

James, thanks, that's another clue. I never did have much oil, if more than the odd drip, pushed out of the rear scroll. So that helps eliminate sump pressure I think, at least as a sole or significant factor. Maybe that's the only way to work this out. Elimination.

Lawrence Slater

All good stuff this! Just to clarify, my engine did not have its cam bearings replaced when it was rebuilt and as I have had that engine for many years they are the original factory bearings. Crankcase pressure may be a possibility but again my engine is really dry and there is no leakage from the rear scroll.I did renew the cam plate to minimise end float Two thoughts however: Are the timing covers different. Mine is a very early 1275 and would have had the early valve type sealed system, ie not using the Y piece. Did the later covers have some sort of restrictor or valve to compensate for the different suck? Second thought concerns oil pressure. Mine is 70-75@ 3000 rpm hot. Cold it reaches about 80 at 1500 rpm. Does this pressure have some impact on the amount of oil in the timing cover? On the thread of too much crankcase pressure would that not be an issue all the time with the resulting clouds of blue smoke?? This only occurs at a specific moment and sometimes not at all!! I agree race engines are different. Mine had a big take off from the rocker box and the timing cover feeding into the catch tank. I never came across oil pumped into the tank over my 7 years of racing.

Bob Beaumont

Bob, "Are the timing covers different. -- Did the later covers have some sort of restrictor or valve to compensate for the different suck?" Good question. Mine too began life with the Mushroom device, which I discarcded in favour of the y piece. The mushroom connected directly to the manifold, and when I simply connected the y piece in the same fashion, I sucked up a lot of oil. Then --- from memory --- I must have aquired later HS2 carbs with the spouts to receive the y piece. It never occured to me to compare the front timing covers. Then I aqquired my spare engine, and have no idea now where from or what setup it was. I don't even have an engine number for it to tell how early or late it is. ---- that's my spare, the one with the same problem as yours. "Second thought concerns oil pressure. --- Does this pressure have some impact on the amount of oil in the timing cover?" My readings on my spare engine, were similar to yours, and are much the same on my current engine, without the problem. So my guess, as Guy also said, is that there must/could be, some factor - X, that brings all this together, to produce the goldilocks conditions for the oil to be sucked up. I agree with you about the crankase pressure too, because I haven't seen the results at the oil dipstick, and I would have expected to. But perhaps momentarily, in some yet to be understood way, the ring sealing fails to momentarily increase pressure? Seems doubtful though. I have no choice. as my spare engine is sitting in the garage, with the head off, I think I'll pull the timing cover, and take a peek. I don't expect I'll notice anything I didn't see before, but if I take and post pictures, maybe somebody else will. Wanna come and observe? Only joking, you've got your own issue. :)

Lawrence Slater

The inlet to the canister thing on the front of the chaincase is quite high up, at least higher than I expected. Without dismantling it is difficult to measure accurately, but it must be nearly level with the lower edge of the cam bearing shell. Which means that for your "suck and blow" scenario the chaincase must be quite deep in oil. How does it empty back into the sump anyway? The engine front plate must seal it in pretty effectively until it reaches the level of window hole through to the block.

Guy

That's exactly right Guy. I once thought about finding a way to fit a clear window into the timing cover, so as to allow me to see the level the oil reaches. Then I came up with the idea of the clear plastic breather pipe. It follows then, that if there is a solid column of oil in that clear breather pipe, then the seperator must also be full of oil, and that equates to the internal hole being below the oil level inside the timing cover. I too found that hard to believe. But there is no other way to explain how a solid column of oil is sucked up the breather pipe. As for draining, if you refer to my picture of the front main cap below, there are two holes in it. From what I can tell, that is the only way for oil to drain back. Those holes are pretty small. So if they were expected to cope with more than the designed amount, then the cover would eventually fill with oil, as it must be doing for that specific period of time. From there I assume, that the delivery of oil is too great, and since the only two places that deliver the oil are, the splash feed and the front cam bearing, one of those has to be the culprit. I favour the cam bearing.

Lawrence Slater

Sorry but I just don't buy into the explanation - If the timing chain cover was running that deep in oil, why would you design into the engine the thrower ring on the crank chain gear end... The chain would run in a constant oil bath. If the cover filled up with oil to that extent (even accepting it only did it on some engines) - i.e. if the supply to the cover exceeded the ability of the oil to drain through the main cap holes - then what would stop the engine pumping all its oil out of the front cover breather...? Incidentally the canister on the front breather is filled with a horrid (usually filthy/gungy with oil) plastic gauze material - Bill Richards always used to dig it out and run without it on the engines he built - given that he learned his trade from Henry Stone's son at BMC Special Tuning I have always done the same.

James Bilsland

James, that's the point. It's not designed to run that deep in oil. There is a fault. An uncommon one, but a fault nonetheless. May I assume that you accept I am not lying or mistaken? If you do, then can you explain how a solid column of liquid oil is sucked up the breather pipe into the inlet manifold? As regards the cannister. Earlier I explained that I tried removing the wire from the interior, and that didn't solve the problem. First I soaked and cleaned it in petrol, and when that made no difference, I removed the wire. "then what would stop the engine pumping all its oil out of the front cover breather...?" Nothing would stop it at all, if it continued. But it doesn't continue, it is a short duration fault, that only occurs at the correct temperature. It is not a design feature, but rather a developed or user created fault in my engine, and it seems Bobs too. If I knew why and how, I would have fixed it long ago, and Bob wouldn't have posted it here either. :)

Lawrence Slater

Lawrence, I would have expected the main source of oil in the front timing cover to be from the front main bearing as half of its oil supply should drain into the timing cover.

David Billington

David, that's something I hadn't considered, thinking that the only supply was the front cam and as I am now aware, a splash feed. If so, then I wonder if I/we have a front main beating problem? Mains rumble when they fail, as I recall, and I don't remember hearing that. However, if only the front had a problem, and there was excess "play". maybe too much oil could escape. But oil pressure would fall if the mains were leaky, --- I think.

Lawrence Slater

Could the covers be the problem then. Both Lawrence and I are using the old type. Does anyone know what a later type cover looks like ie one which would have been used with the Y piece ? Does it have a different part number for example. Unfortunatly my spare 1275 is also an earlier one so may be no good! I don't buy the cam bearing argument too much as mine haven't been changed from original manufacture.

Bob Beaumont

What do we know? We know that oil is being sucked up the pipe. We know that for that to happen there must be a supply of oil. We know that the front cam, the splash feed, and possibly the front main, supply oil to the timing cover. We know there are two drain holes in the front main cap. I know, I checked mine on previous occasions, and they weren't blocked. What don't we know?

Lawrence Slater

1098 cover is different, it doesn't have a canister The take off for the breather was from the side cover, and that led to the mushroom device, straight to the manifold. Looking in my old parts catalogue, for the Sprite and midget Center in Richmond only one part number is listed for the 1275, with canister attached. 12G 2507.

Lawrence Slater

OK, two comments. For Lawrence's (as yet unproved) hypothesis ;-) to work only requires the oil to fill the chaincase to the level of the inlet of the cannister, It doesn't have to fill right up to the top of the cannister5. Once the inlet level has been exceeded, then suction would take over. But even then for the level to rise up that much does seem pretty unlikely. It certainly isn't designed to run as an oil bath system! Lawrence, those two holes on the front of the bearing cap are not drain holes. They are threaded, and where the two bottom countersunk machine screws go in that locate the engine front plate. There must be some other oil passageway back past the bearing cap

Guy

One way I used to think to resolve this, along the lines suggested by James, was to drill into the old mechanical pump blank on the side of the block, and fit the canister there. As there would only be a splash feed, I figured this might be a solution. But I wondered about the effect of sideways oil surge in the sump. If the level in the sump rose up to the level of the blank then the same would ensue. So I gave up the idea. Also, I just can't help thinking, there is a really simple, if obsure, fix to this. It's so rare, that it ought to be pretty obvious how to fix it. All you have to do is identify the cause. LOL.

Lawrence Slater

Yes, of course you're right guy. Not having a cap in hand, I can remember there are drain holes, and from the picture, thought those were it. So where are the holes? They must be at a low level. Edit, if you look closely at that picture, there appear to be two more holes in the groove of the cap.

Lawrence Slater

Here

Lawrence Slater

Ah, yes. Didn't spot those and it is a long time since I built my engine!. Very small holes for thick viscous oil to run through unaided, when it is still cold. I think, bottom line is that the problem as described is caused purely by bad driver habits. Anybody with a modicum of engineering sense knows that you should drive gently and let an engine warm up properly before stressing things by accelerating hard.

Guy

Yup, that's me :) I've always been an impatient and bad driver. :) And believe it or not, I did indeed on ocassions, start the engine, let it warm up, then turn it off for a while and let the oil warm up, before driving off. It worked too sometimes, but I often didn't have the time or motivation to go through that ritual. So it was a case of choke those behind me, suddenly pull over to the side, let the engine die to tickover or stop it, wait 30 seconds, and then drive off again. That worked most of the time. But not very satisfactory or efficient, and a bit of a failure, since I am a bit fussy, and like things to work to an order, --- mine. :)

Lawrence Slater

LOL, Lawrence, just teasing! Given the route through the oil galleries the feed to the front main and then on to the front cam bearing is bound to receive a highly pressurised oil supply, especially when the oil is cold and wont flow on and out of the rocker shaft feeds that easily. It will build a high pressure and seek the nearest exit! So one can imagine oil being pumped under some pressure past those bearings and into the timing chain chest. As cold oil then only drains out slowly under gravity through those two small holes, then this could well account for it filling up sufficiently for the suck and blow scenario. Once the oil has warmed it will a) continue on freely out via the head and rocker shaft galleries, so less will be forced out past the main and cam bearings, and b) oil arriving in the timing chest will be runny enough to drain rapidly back to the sump so the chest won't fill up as before.

Guy

:), but many a truth in a jest Guy. :) You got me bang to rights guvner. lol. Here's a better picture of the front main cap, just about showing the drain holes. --- Also Haynes, probably the best after market workshop manuals in the world. :) Easy to see how those holes could become blocked, but I specifically remember making sure they weren't. I wonder if, after I had bolted up the end plate, gasket goo or even the gasket, partially filled the holes. Or if some muck from the canister or elsewhere, found it's way in to one or both of them. The only trouble with that theory, is that I pulled my engine apart and checked just that at least twice. I'll pull my spare apart tomorrow, and take a picture of what I find. But I expect to find both holes clear.

Lawrence Slater

My point was that if you imagine pouring thick cold oil through one of those small holes it would be a very slow job! Whereas the oil coming in, although equally thick, is being pumped at 80 to 100psi so will be coming in a lot faster. Even given fairly fine tolerances on the bearings, the surface area is quite large, so I think sufficient to cause the bath to fill faster than it is draining.

Guy

Yes, I got your point Guy, and I needed a cuppa and 4 choc digestives to lube my grey matter before responding, ---- that you may well be onto something here. Bob hasn't changed his cam bearings. Mine are slightly recessed. As you say, when cold there could be excess pressure at the cam bearing. A midly worn, or recessed one could allow more oil to escape than intended or desireable. Moreover, if as you elude to, the escape route to the rocker shaft were to be partially blocked, or the shaft partially blocked, -- not enough to starve the rockers, but enough to further raise the oil pressure at the front cam bearing, then the only way out for the oil is the timing cover, and the rest is obvious. What's your view?

Lawrence Slater

Agreed, and think of it this way, those oil pathways ARE partially blocked - with slow moving thick viscous oil, at least until it warms up

Guy

So what's the missing factor, that prevents 1275 engines, from having this problem? There must be one. I thought of the cam bearing as being the prime cause, and bobs "might" be worn, but how about others engines? Why doesn't it happen to everybody? Could the problem lie in the route to the rockers?

Lawrence Slater

>>Also Haynes, probably the best after market workshop manuals in the world. :)<< after putting that you'd better hope that's a photo that corresponds to your particular engine and there were no alterations in that area before or after that photo – the Haynes timeline is a very wavey one – remember Haynes printed errors on front road springs that’s not the only error in the whole manual that even I know of look and I only look at the few pages I understand :) I’m sure they’d be 100% correct on engines though ;)

Nigel Atkins

Here's a thought I've just explored. The oil from the front cam bearing is ported up through the block to the block face. From there it enters the head, and on into the rocker shaft. Q. What if the head and the block oil feed hole for the rockers didn't line up fully? I have an Austin 1300GT head. Bob has a Slark modified one. Both are 12g940 castings. ---- I rang Slark, and they confirmed that they supply old modified 12g940 heads in various stages of tune. I asked how late an engine the head went up to, and if maybe it changed a little, with respect to the alignment of the oil feed to the rocker. No, they align perfectly. But, what if, I and Bob, just happen to have a head, that has an alignment problem with the oil feed to the rockers? Possibly bad castings? Rare, but faulty in some way. If so, then the hole in the top of the block might be partially obscured. Not enough to cause rocker shaft starvation, but enough to slow down the passage of cold oil. Initially the oil coming from the front cam bearing is too cold to escape in sufficient amounts to fill the timing cover, -- or, ---- from the moment of cold start, it is beginning to fill up. Either, at the right temperature, the oil becomes thin enough to escape in a greater quantity, that it suddenly fills the cover, or if filling from the start, it reaches the critical level, and enters the canister. In either case, when the reaches the critical level, the oil will be taken by suction. Then as the temperature rises, the oil thins further, and draining becomes adequate to cope with it. ---- Both of us try to take action to minimize the oil suck by lowering the revs, so we give time for the drain to "catch up" with the supply. Then the moment passes, and the oil is thin enough to travel up to the rockers in a greater flow, the pressure is lower, so that less in pumped into the timing cover, and the oil is thin enough so that it drains quickly enough. Possibility? Nigel, I doubt the drainage has changed, someone would know about it. I hope. and anyway, mine is definitely like that. :)

Lawrence Slater

>>Nigel, I doubt the drainage has changed, someone would know about it. I hope. and anyway, mine is definitely like that. :)<< well you're alright then Jack :) don't meant to detract from the thread but you already know to check, cross reference and question information from all sources I'm just putting it for (potential) future readers

Nigel Atkins

Standard or high output oil pump Lawrence? Standard oil pressure relief valve or had you put in a longer spring or added a ball bearing?

Guy

Almost certainly standard, and I think Hobourn Eaton. I remember measuring the play in the vanes and reusing it. Standard oil pressure spring, and no ball bearing added. Just the standard plunger. My start up oil pressure has alwys been much higher than 60psi, and even hot would achieve that. -- Interestingly, I've read that's a bad thing, as it causes a drain in power, by making the pump work too hard, and reduces oil efficiency, by causing too much heat in the oil.

Lawrence Slater

And just to put this into the mix ------ ; Here is a picture of the front journal on my spare camshaft. It’s a piper 270. This was in my spare engine when the oil sucking problem started. I removed it, as I wondered if it had anything to do with the problem and never put it back. The problem persisted, and it's been lying around, getting a bit damaged ever since. Note the oil grooves. I assume these are the same as on the original factory BMC cams. Without knowing the exact design requirements, it’s obvious that they serve to distribute the oil, -- to lube the journal, feed the rockers, and supply the timing cover. I think it’s obvious the one I have marked feeds the timing cover. So I think it’s confirmed that the timing chain is fed under pressure from the front cam bearing. Does this groove sweep directly over the oil feed in the block, and then line up with the hole in camshaft end float control plate? If so, a small controlled amount of oil "should" be pumped into the timing cover. If there is a problem in this area, of whatever nature, could the oil supply exceed the amount required?

Lawrence Slater

I think an excessively high oil pressure also implies a relatively lower volume of oil passing over the bearing surfaces, so less efficient heat removal from the hot spots. If your pump is standard, and so is your relief valve, have you ever wondered why the oil pressure is so high? (assuming an accurate gauge) If the relief valve is designed to open at 60, or maybe at 70psi, then surely this should be the limit that the max pressure achieves? Maybe you have other restrictions coming in to play?

Guy

If someone has an engine to strip it would be worth measuring the relative heights of the hole in the block versus the one in the timing case. Using a rough and ready paste up it seems the top of the vent hole coincides with the middle of the one in timing case. When oil is too thick to drain from the front bearing the cover will splash fill to the level of the white horizontal line. Add the timing gears whizzing about in all this oil and you easily have a recipe for high vacuum to gargle oil up into the inlet manifold.In fact the timing cover hole is almost perfectly placed to fill given the direction of rotation.

F Pollock

Welcome back Fergus, you posted just as I posted my pics of my front cam journal, and guy asked me about oil pressure. :). Great alignment, and helps a lot to visualise all this much better I think. If I can, tomorrow I'll pull the timing cover on my spare engine. Guy yes, it's possible I have a partially blocked bypass on my current engine, as that too has excess high oil pressure, and maybe I did/do, on my spare. But the current engine doesn't have this problem, although it did, until changed to an HIF44, as described in an earlier post in this thread. I'm off to make my dinner, then I'll be back.

Lawrence Slater

Good to get someone else in on this long speculative discussion! And someone who knows what he is talking about too ;-) That is sort of what I was saying earlier, about the level of the intake end of the canister. The only thing I would question there is the position of your white line. Shouldn't it be on a level with the lower edge of the labelled "opening to the block interior)? When drainage via the two small holes in the front main cap is inadequate, this opening must be the limit of oil height rises to before it overflows back into the main block. Way back in this discussion I mentioned that this hole is often quite ragged, as if the casting leaves a thin web that is then knocked out. If it isn't fully knocked out or cleaned up - which they appear often not to be - then some blocks may in effect have a higher overflow level than others. And maybe this is the root cause of Lawrence's problem?

Guy

Right, so the cast hole isn't a splash feed at all, but an overflow to prevent the very thing under discussion. That would make sense. I was trying to put myself in the mind of the designer, and thinking about that hole and it's real purpose. ---- I was wondering if it was in fact a sump pressure relief into the timing cover, and hence the canister to the breather. ----- But as a splash feed, it's a bit poor. After all the rods are going up and down, and not obviously throwing oil into that hole. But the obvious didn't occur to me. An overflow for a potential problem. After all you don't exclude the possibility that a toilet cystern will overflow. You allow for it, with an overflow pipe. Could I have blocked mine, either completely or partially, or is it inadequate in some way related to the other thread you mention Guy? So is the problem, not too much oil, but not enough drain, and poor overflow? And could that be the solution regardless of oil supply? Simply open up the overflow hole. First thing to establish beyond doubt, is that the relative heights of the canister entrance, and the "overflow" hole make this plausible. It had also occured to me long ago ---- although I have no proof as I haven't mentioned it here ---- , that the cam bearing squirts directly into the mouth of the canister. But I largely discounted that as the prime mover, as it couldn't by itself fill the canister. The oil would just run out. So I figured that wasn't significant of itself, until the timing cover was full enough.

Lawrence Slater

Lawrence, The cam bearing can't squirt directly into the breather as the cam thrust plate is in the way as is the cam sprocket.

David Billington

David, you beat me to my own thoughts. Teach me for thinking out loud in text. LOL. Yup the sprocket is in the way. But there is a hole in the cam plate cover, to allow the oil out, albeit behind the sprocket.

Lawrence Slater

If an extra hole the same size were drilled in the front face of the block, or indeed the existing one enlarged, to provide for extra overflow, how much would that weaken it? Enough to promote a failure? I'm not contemplating this, as I want to know why this is happening. Just musing possibilities

Lawrence Slater

Duplex gears will no doubt exacerbate the issue as you effectively have twice the paddle boat effect holding oil and dragging it up in the direction of the cover hole over a simplex arrangement. I think if it were possible to raise the cover hole opening to the upper edge of the casing you'd have enough separation for the oil fill not to occur. It may not be possible to drop the casting hole in the block, but widenind the base dimension and radiusing the outside edge may help 'drain away' more quickly.

F Pollock

Seems a lot of hassle when all you have to do is allow the engine to warm up properly before driving hard! If the whole issue does relate to how well that hole overflows back into the block, and given that this seems to be a fairly rare occurrence (i.e.most people haven't experienced it)I still wonder if it is caused in a limited number of cases just because the rough casting of that hole hasn't been opened up properly during manufacture. The rough appearance of that hole was commented on - with photos - a year or two back. It really did look at that time that this "window" was initially sealed when cast and possibly opened by a sharp tap with a hammer during production. It could explain why an occasional one isn't fully opened up.

Guy

I'll look tomorrow. And at this stage, I really still favour pinpointing the exact cause, and then remedying it. The fact that it happens so rarely, must point to it being identifiable, if only one knows where to look. Unfortunately, driving it really carefully whilst the initial warm up takes place, doesn't always work. It can strike anytime, and puts you on edge waiting for it. If it were just a puff of smoke, it wouldn't matter so much, but the only reason I managed to make my engine last so long was because I was careful during that warm up period, in the cold weather. That became really tedious and boring. If I hadn't been so careful, the hydraulic effects of all that oil in the bores I reckon, would have cracked the rings at least. And although I did get over 100thou from the engine before taking it off the road, I think I would have got more without the problem. When the engine came out, it was because it was showing signs of worn rings, -- smoking a lot more of the regular kind, and losing power. When I pulled the head, I expected to see perhaps a blown HG and or worn bores. Instead the bores are so good, I reckon I can just re-ring it. There is some sign of hg between 2,3, but not that much. I've seen far worse. But I haven't pulled the pistons yet, and expect to see the rings caked in hardened oil. No, when this engine goes back together, I don't want to wait expectantly for the next gulp of oil. Some faults you can live with, but only once. A bit like a bad marriage I reckon. You might do it once, but you wouldn't repeat it with the same person. I just want to get in, and drive with gay abandon. LOL. Not that you can anymore on our crowded roads. :)

Lawrence Slater

If it were possible to see into the inside of the timing cover, from the moment the engine is started, it might be possible to watch the rate the cover filled with oil. If my engine was in the car and capable of running, I'd remove the timing cover, and cut a hole in the face, and insert a perspex sheet. Then I'd put it back and see if I could get an angle to watch what happens when it starts. Or, If my engine was in the car and capable of running, I'd remove the timing cover, and remove the wire in the canister. Then I'd put it back and leave the breather pipe open. The I'd insert one of these, if I had acess to one. Maybe you could see what happens. £185 quid plus postage on Ebay. http://tinyurl.com/7n7wwf8

Lawrence Slater

I've had this smokescreen happen on a motorway decelerating for a slip road so warming the oil doesn't necessarily prevent it.It was definately the breather as once left open to atmosphere and the mushroom plugged with a handy spark plug it never reocurred. I now run 3 breathers into a catch tank and it always stays empty.I think the duplex paddle effect may be the key ingredient, as once the crank gear and chain are partly submerged, oil will be flung food blender style against the walls of the cover. When manifold vacuum is high enough oil can be pulled into the canister and once 'plugged' hydraulics take over, giving Lawrence his solid column of oil. Excessive crankcase pressurisation will have an effect as a push me pull you with manifold depression, and at certain revs this may slow or even stop oil drain from front bearing cap - effectively allowing the cover to fill - as Guy correctly said, to the bottom edge of the opening. Agree limiting the pressure relief valve to blow off at 60 lbs cold should reduce the fill rate along with reducing pump load and changing to an A+ single chain and tensioner, would probably reduce the blender effect and additionally take out backlash at the drive spindle to give better timing control.

F Pollock

The obvious simple solution is to adapt the chaincase cover by moving the canister inlet higher - a fairly simple cutting and welding job. - Surgery that is unlikely to have any unwanted side effects. It would probably only need to be lifted by a fairly minimal amount and it isn't at the highest point anyway. I had always assumed that the wire gauze stuffed in the canister was to catch oil vapour, and condense it (canister is in the direct cooling air flow from the fan)so that it ran back into the chaincase. An effort to reduce the amount of oil in the vapour actually pulled through to the manifolds without reducing the suction effect which controls crankcase oil leakage. OTOH perhaps it is more to do with limiting oil surge into the canister - acting a bit like a beach groyne limits wave action. I do wonder that this sort of development isn't documented somewhere. And no, I do not mean in the Handbook! I mean the BMC design teams and Special Tuning must have written down their test findings and made detailed notes of stuff like this as it was added and tried out on their test engines. It would be good to know what their thinking was, what was tried and rejected and why a particular solution was chosen. It would make fascinating reading! If only....I guess huge amounts of this sort of paperwork was just shovelled out and burnt when they were closed down.

Guy

So are we saying its: a) Higher than normal crankcase pressure b) Higher than normal oil pressure c) The effects of the Duplex chain d) Condition of cam bearings e) High manifold depression Some or all of these factors all come into play at a certain oil viscosity usually when warming up (lawrence and I don't get the problem when its warm). My gut feeling is that its engine wear although there are ways of reducing the problem. Fair summary??

Bob Beaumont

I am not really convinced about the duplex chain theory. To me it would seem that the direction of rotation means that the part of the chain running near to the cannister opening, is running downwards, and if anything would drag a high oil level down at that point. Although if not actually running part submerged in an oil bath it would certainly be flinging oil about a lot! I think that the hight of the overflow window is critical too. If on some castings this isn't properly cut out, then there could be a slightly higher threshold level, retaining more oil in the chaincase. Anyone else spot we passed the 100 message mark!

Guy

Many years ago I ran a Formula Junior engine in the Frogeye and was plagued with giant oil leaks from the rear main bearing - The engine was pulled and rebuilt more than once like a Swiss watch, but using a 13/1 compression ratio and 8500 rpm easily overcame the capability of the rear scroll. In desperation I ran Special Tuning and to my surprise was put through to Stuart Turner who was Competitions Director at the time. He explained it was a common problem and that the works engines were using a rope seal on the crank to reduce the flow, and suggested I try the same. But it all sounded a bit dodgy to me and I ran the car with 3/4" open breathers instead.

F Pollock

A decent cricket score then Guy. :) I was still going to write, -- that irrespective of the suggestions, it is fairly unique. Now I'm not so sure. Fergus has had (still has disguised), the same problem, as he describes the slip road incident. That's the same can of beans. So there must be more out there albeit unrecognized and perhaps avoided by extra breathing. That now begins to suggest to me, a design/manufacturing problem, on at least 3 engines (4 if you count my current engine, that now has an HIF44 that appeared to "fix" the problem). I said before, once Bob reported the same as me, that there has to be more. Yup Guy, I have been searching the web, for exactly that. The original design and test information for the A series engine. Surely someone must have something. How about the B series. Is that the same arrangement? I remember Rob, posted original BMC plans for the Stub axles, re the Front wheel bearing saga. Rob, where did you get those, and does the same source have detailed original engine specs? Bob, I don't think it's engine wear per se. My spare engine didn't exhibit this problem, until I had it bored, had new cam bearings fitted, and swapped the original for the 1300 GT head. And the Piper 270. The 270 was excused, as I took it out, and the problem continued. There is some other commonality. Poor block casting as Guy says? I agree, they must have tested/evolved this system in various forms. Maybe it is so close to overflowing all the time, that on some engines the tolerance is just too fine, and up it sucks. If the rate of flow from the front cam could be guesstimated, it wouldn't be too difficult for a fluids engineer to work out how quickly the 2 main cap drain holes can empty the cover. As you said before Guy, pouring thick oil through them is going to be a slow task, so they may well be too small to begin with. As James said, what is the point of the oil thrower, if the chain is sitting in a bath up to it's neck? My feeling is that the "overflow" should never be reached, ideally. It's a toilet overflow, and you always set the ball cock a decent amount below the overflow. Oil is delivered under pressure via the front cam bearing. I think that’s agreed. On some engines, there is too much oil in the cover. Why? I'm off to my garage, to pull my front cover. I may be some time. :)

Lawrence Slater

Amazing coincidence that a post has appeared on the AHC forum with the same problem! relates to 1275 engine in a frog but using original breather arrangments. Its not clear what has been done yet. Will report back!

Bob Beaumont

Positive Crankcase Ventilation PCV. That mushroom device. The PCV Valve. It was connected to the manifold, and at high vacuum, it closes, and prevents suction down the tube. Remove the insides, and apart from a weak mixture, you’ll suck up oil. I’ve proved that long ago. BMC new that, that’s another reason for the diaphragm . The Y piece connects to the carbs, at a point of more or less constant depression, according to my book of words. Does the HIF44 exhibit less vacuum at this point than twin HS2’s? Anyway, the point I’m making is that if the vacuum is too high, oil will be sucked into the breather system. If the engine is modified by the owner, and the design/manufacturing tolerances of this system are too close, as they might be on some engines, when the moment is right, oil is sucked up. Extra oil pressure, sump pressure, vacuum, and temperature, all combine on some engines, in just the right combination to cause this problem. There is no one single cause. Bob, you summed it up correctly in your last post, as did you Guy, when you said it was a complex set of circumstances. So the question is, what is the simplest, most efficient, and elegant way to fix it? ---- Now I'm really gone to my garage. :) Edit. Excellent Bob. Fantastic. :)

Lawrence Slater

The solution just hit me. Go back to the PCV. No suction, no oil in the inlet.

Lawrence Slater

The PCV was used when the breather system is connected to the manifold, which has at times a high depression = too much suction. It was abandoned and the breather pipe routed to the carb body. This gives a lower, but more consistent depression that doesn't need the extra gismo to control it. Normally. So was the PCV abandoned just as a cost cutting exercise? Simpler is better? To limit crankcase pressure and consequent oil leakage one must need quite a good level of suction to be maintained. If too much air is drawn in via other vents in the system then even greater suction would be needed. This goes back to the very beginning of the thread where Lawrence commented on the need for a decent washer seal on the dipstick tube (or was that on the other discussion?) Anyway, my point is this - if too much air gets in the only way of keeping the pressure inside the engine down is to apply more suction. And if on occasions this coincides with an oil surge then you will get the suck and blow scenario. Conversely, too air tight a system and since air isn't drawn through by the sucking system then the only thing left that will move is the oil! It must be a fine balancing act!

Guy

Yes it's important on a closed breather system to retain the black breather cap on the rocker box as the single source of air into the engine. Chrome oil caps don't do this. But whether you have a PCV valve or breather to carb body you'll still need to manage the oil so it doesn't end up going up the spout. If you compare early and late timing covers you'll notice the early cover has a tiny splash ring that covers 3/4 of the cam sprocket. The later one is considerably deeper and runs unbroken all around the sprocket.In addition the outlet hole has been moved up as far as the spot welded flange will allow. Was this a Factory move to fix the problem? Adapting early covers to replicate this condition - and even bringing the splash guard closer to the recessed part of the sprocket may well keep excess oil from entering the spout in the first place. Once the oil has been kept away so that the chimney can drain more effectively, either of the closed breather systems should work with negative pressure without fear of ingesting oil.

F Pollock

Here's a picture of what I mean.

F Pollock

this is about all I can contribute to this thread >>Yes it's important on a closed breather system to retain the black breather cap on the rocker box as the single source of air into the engine. Chrome oil caps don't do this.<< (unless I've misunderstood this) - whilst I'm a fan of the vented, filtered, black plastic oil filler cap the chrome oil caps are available with a hole in them but I was told they're not as good to use as the black plastic ones

Nigel Atkins

For "looks", I changed my black plastic, vented, gauze filled one to a chrome vented one last summer. Can't say I noticed any change - apart from the shinyness of it.

Guy

The chrome ones typically have a tiny hole in the center but it's too restrictive to vent.The pucca ones vent and filter and are supposed to be changed every 12000 miles.

F Pollock

Ho Ho I think we may have something. The reason for the loss of the PCV makes economic sense. Providing the engine is in good shape and /or hasn't been messed about with by people like me and laurence then the revised sealed system works - just! Immediatly you change one of the parameters the risk increases. Now in most cases modified engines either run with no sealed breather system or have a different carb set up hence no problem and no oil in catch tanks etc The solution may well be to modify the existing old type cover to the later A plus spec. or indeed fit a PCV or have an open system breathing into a catch tank.

Bob Beaumont

I have used the later cover on some race engines with a tensioner on a duplex chain (see what I did there? ;)). There is a small issue with Spridget front engine mount plates in that they are designed for the older cover design and you sometimes have to relieve a small amount from the stiffening section of metal on the right hand side of the plate as you look at it

James Bilsland

Not quite as clear cut as that Bill! My engine is similarly modified, and I don't get the big blue! 1330cc; 276 cam; 10.5 comp; HIF44; electronic; lightened and balanced crank; MG Metro big valve head,Titan and Maniflow manifolds. Oh, and at 65+ K it is well worn in, if not worn out! Lawrence will find all of this familiar. Mine breathes to the HIF 44 carb, and prior to that via a Y piece to twin SUs. The breather pipe goes via a catch tank, but is still sealed as I believe in suction! I was getting the mild blue version which as I explained early on I believed was oil condensed on the inside of the breather pipes. Adding the catch tank seems to have cured that, although it doesn't seem to fill up much. Maybe just a bit in the bottom of the can last time I looked.

Guy

Yes after a many years of spent fiddling that's what I've ended up with. I have a Duplex with tensioner on the 1330 and the standard A+ set up on the 1293. I run both with 3 breathers all open to atmosphere to keep the induction free of ingesting fumes. One has a Peter May oil seal at the back and the other has retained the scroll. As neither of them puff,smoke or leak I've elected to leave it as is.

F Pollock

For 14 years, because of this oil problem, my spare engine has been like a brooding beast, in the corner of my garage, and in my mind. The beast is dead. I know what the problem is. I'm just writing it up a little clearer, and reducing the size of the pictures that illustrate it.

Lawrence Slater

This was a surprise, and probably rules out forward oil surge, unless you're standing it on it's nose. Back later, I need to eat.

Lawrence Slater

Despite what I said earlier today, "There is no one single cause." I retract that partially. The prime cause, is the front cam bearing / camshaft endfloat. I would say that the all conclusions drawn in this thread are relevant. The suction is poorly controlled, and because of the design, the potential for oil being sucked into the inlet manifold exists irrespective of other faults. The sump pressure is also a factor, as is, draining, overflow, and oil splash and churn. IMHO of course. :) But the prime cause is the oil feed. Specifically, when there is too much of it. And that connects it all together. The timing chain and sprockets need lubrication, so they are fed a supply of engine oil. The sump needs to breath to assist the life of the oil and remove sump pressure, so it is positively vented via the inlet manifold/carbs. Both of these requirements are met in the single chamber of the timing cover. And that's why the potential problem of oil being sucked into the inlet manifold exists. How is the oil supplied to the interior of the timing cover? Oil is fed via a small hole in the Camshaft end plate, in conjunction with a lengthwise groove in the front portion of the front camshaft journal This groove extends to the front face of the camshaft. The end plate has two functions. It controls end float, and it allows for the delivery of a measured squirt of oil, under pressure, once every revolution of the camshaft. It is not intended to fill the timing cover. It’s supposed to be just enough oil to ensure the sprockets and gears get a decent soaking. How does the timing cover drain of oil? It’s designed to drain via the 2 drilled holes in the front main cap. The problem. If too much oil enters the timing cover, the 2 small drain holes can’t cope, and the oil doesn’t drain fast enough to prevent the oil rising to an excess level. The timing cover begins to fill. The oil level reaches a hole in the front face of the block, and should overflow back into the sump. However, this hole is, a) too small (circa 9/16ths inch), b) subject to reverse pressure from the crankcase, and the suction from the crankcase breather system, c) in a battle with the timing chain and sprockets, churning the oil past the hole. In addition to that, surprisingly, the bottom of the overflow hole, is set at a higher level ( 8 and 13/16th inch from the base of the sump), than the bottom of the internal entrance to the crankcase breather ( 8 and 10/16th inch from the base of the sump ), on the front face of the timing cover. Hence, the filling oil, begins to flow into the crankcase breather canister, BEFORE, it begins to try and overflow back into the sump. The level of oil, assisted by the suction exerted by the breather system, continues to rise in the timing cover, until it completely covers the breather entrance hole. At that point a vacuum is formed in the breather canister and external pipe, and oil is sucked into the inlet manifold. The prime cause. The intended amount of oil is designed to be regulated by the hole in the camshaft end plate. This is further controlled by the once in 360 degree alignment, of the groove in the camshaft and hole in the end plate, the small amount of end float in the camshaft, the correct clearance between the journal and the bearing, the oil pressure, and the correct placing of the front camshaft bearing in the block. Four of these can give rise to too much oil being allowed to enter the timing cover. 1). If the journal/bearing clearance becomes excessive, more oil will escape under pressure into the space behind the end plate. This space is limited by the cam plate, which controls end float 2) If the end float is excessive, more oil can escape via the much larger opening in the end plate, rather than the intended oil feed hole. 3). If the bearing is placed too far back in the block, then more of the front of the journal is exposed to “air”, and the groove is sweeping free of the journal, hence feeding the space behind the end plate, and hence the timing cover. 4) Too much oil pressure. Clearance between the camshaft bearing and journal is given as 0.001 – 0.002 in. End float is given as 0.003 – 0.007 in. My engine on inspection. The engine has not been cleaned since removal. (14 years since). There was little to no evidence of excess internal sump pressure. The rear of the sump was largely free of obvious oil drip from the rear scroll, and in use I don’t remember much. The timing cover bolts, not surprisingly after 100thou+ miles, were almost lose. But there was no sign at all of oil leakage from the gasket, which I would have expected if there had been much internal sump pressure, and hence timing cover pressure. On removal there was oil sitting in the base of the timing cover, up to the level of the drain holes, which are above the lower extremely of the timing chain and sprocket. The oil was clean and in good condition. The bottom of the breather canister was clear of obstruction, and had oil sitting inside the lower portion of the canister, just above the internal entrance hole. The metal wire mesh (I believe it is metal), was clean apart from oil residue. When the chain and sprockets were removed, the drain holes could be seen to be completely clear and unobstructed. The overflow hole was clear and unobstructed. With the camshaft removed, the oil feed to the head/rockers was clean and completely unobstructed. It’s debatable if the front camshaft bearing is set too far back. So I exclude this (for now). The front camshaft bearing is badly scored near the front, and there is 0.002-4/5 inch clearance between it and the camshaft journal, at this section of it. The end plate is badly worn and end float is at least 0.013 inch. The overflow hole diameter measured at 9/16th inch, and the breather canister entrance hole at about 1 1/16th inch I know that this engine had oil pressure when cold in excess of 80 - 90psi, and when warm, was still in excess of 60psi in the mid to upper rev range. I conclude that oil is being continuously fed under pressure (perhaps too much pressure ), into the timing cover, rather than the intended once in 360 degrees revolution of the camshaft. This combined with the inadequacies of the drain and overflow system described above, fills the timing cover far above the desirable level. The result. When starting from cold, in cold ambient temperatures, after initial warming of the engine, the oil reaches a critical viscosity. At this point the oil is still too thick to drain fast enough, but has become thin enough, to flow more freely under pressure into the timing cover, filling it to and beyond the overflow, and hence to the breather canister where it is taken by vacuum into the inlet manifold. An alternate to this, is that excess flow from the “leaky” camshaft endplate, under too much pressure, is such that oil is filling the timing cover from the moment of start up, and because it’s too thick as yet to drain, or overflow fast enough, it eventually fills the entrance hole to the breather system, and is taken by vacuum into the inlet manifold. The Solution. Replace the end plate and restore the end float to the design specification Replace the camshaft bearings, and also the camshaft if worn. Investigate and remedy excess oil pressure. The drain holes work properly when the engine is warm. So leave as is. Attempt to lower and increase the size of the overflow hole in the block face.. Attempt to raise the level of the breather opening, and decrease it’s diameter. I’ll post more pictures a little later.

Lawrence Slater

Correction The bottom of the breather canister was clear of obstruction, and had oil sitting inside the lower portion of the canister, just BELOW the internal entrance hole.

Lawrence Slater

A good Waking the Dead analysis !

Guy

I always did fancy a dabble at forensic pathology. LOL. Cutting up corpes is a bit like playing with dead engines. Just black instead of red inside. :) Working on supporting pictures.

Lawrence Slater

Here in this composite picture is what I believe, with conviction :), to be the root of the problem. ---- Certainly the case on my engine, and I suspect there must be a cam bearing connection on others with this problem too IMO, since this is where the oil comes from. -- . :) Note the oil feed hole, and the camshaft oil feed groove, lined up with it. Note the badly and unevenly worn end plate bearing surface. Parts of the end plate bearing surface, haven't been in contact with the camshaft at all, and are as new. Where it is worn, it is grooved quite deeply. It appears not to be flat. So even when the camshaft face is pulled up to the end plate, into the wear grooves, and end float reduced to zero at those points, there are still significant gaps between the face of the camshaft, and the end plate. Through these gaps, oil under pressure, can be pushed into the timing cover, even when the oil feed hole and groove aren't aligned, and no(little) oil should flow. When the camshaft moves back to maximum end float, as it would under pressure from the oil being expelled, these gaps are obviously even larger. My measured end float is 0.013inch, but may have been greater, as I measured before seing these wear marks. At other points it could well be more. So perhaps twice the allowed end float. No wonder the oil wasn't contained, and the timing case filled with oil. How much excess end float would it take, to allow sufficient excess oil to cause this problem? Half as much extra as I have? A quarter? The plate appears to have been distorted by it being clamped, to the engine block end plate. I can't find a torque setting for these 3 bolts, did I overtighten them? I cant recall, back at least 20 years. The most I would have gone to is 10lb/sqin. They are small bolts, and I wouldn't have wanted to strip the thread in the block. They weren't lose, but weren't very tight either. Just fingers with a 3/8th rachet undid them. Of course after 100thou+ miles, it's no wonder they might be loser than when first installed. Also, as mentioned previously, I suspect I re-used this plate, this was not a new one. Speculate? More tomorrow. Ug, me go bed now.

Lawrence Slater

Goodmorning Lawrence, late night? I made the waking the Dead reference as your investigations seemed to fit the premise - investigate a long-dead corpse, delving into the innards to find minute clues and then piecing them together to reveal the culprit! I am pretty sure that when I assembled my engine I simply reversed that plate so as to offer up the good unworn face to the end of the cam bearing. I certainly remember that part of the assembly -I don't do many engines so remember these things! I am also pretty tight fisted so I do look for money-saving shortcuts, even though I doubt that cam plate costs much! Or I may have thought about it but found that the three holes are not equally spaced? Given what you have found I would now ask 2 questions - a) Have you ever had problems with wear of the rockers or rocker shaft? If too much oil was being pissed out of the cam bearing then the next thing down the line may have been starved of oil perhaps? b) I would not expect there to be that much axial loading on the cam shaft to cause that sort of wear. I suppose that there is the thrusting derived from the dizzy drive gear, but that cannot be much. Your end plate looks as if there has been a constant hammering action on it, the way the three corners by the bolt holes have deformed. Maybe the faces of your chain gears were not properly aligned and have been causing the cam shaft to move back and forth with every revolution?

Guy

Morning Guy. yep, late night it was, and getting up today, was exactly like the dead awakening :) I assumed the plate, only went one way, and that the dull side was a bearing surface. You're right, the bolt holes are not equally spaced. Also, I've just noticed for the first time, that the oil feed hole, is offset. Reversing the plate, moves the oil feed hole further round the clock face, either anti or clockwise. This shifts this hole, either closer to, or away from, the position of the rocker oil feed hole in the block, whilst at the same time, doing the reverse, with respect to the hole that feeds oil to the front journal of the camshaft from the crankshaft. Is this a factor? Does this positioning matter? Could it have an effect on the amount of oil entering the timing cover? "- a) Have you ever had problems with wear of the rockers or rocker shaft?" Now your are asking. Long ago memories. Was it this engine? I think the anmswer is yes. But on strip found the shaft clogged with that dry oily gunge, as if the rings had gone and the oil had carbonated. One thing I don't seem to have been troubled by, is much rocker cover gasket leakage, or even when running the engine with the rocker cover off, much oil spillage. Maybe that suggests a reduced flow to the rockers. "b) I would not expect there to be that much axial loading on the cam shaft to cause that sort of wear.---holes have deformed. Maybe the faces of your chain gears were not properly aligned --- ? Back then, I didn't appreciate the dual nature of the end float control of the camshaft. I did align the sprocket and chain though, by use of the shims on the crank. I must have discounted, or not noticed the end float of the camshaft at the time. Or maybe not even measured it. There is only one part number. AHU2379. Deceptively called "LOCK PLATE, camshaft". This belies it's importance, and raises the question, how do you set the correct endfloat, if there is only part number, and your camshaft end float isn't set correctly by fitting it? I guess, I just looked at mine, was doing my usual squeezing of every last drop from the pips, and refitted it. Your right about the hammering. I actually think I can recall such a sound, and used rods of wood against my ear to search for it. I wondered if it was piston slap. It was irregular. Maybe it was this. Next up, the front bearings, but please comment.

Lawrence Slater

The pics of the front camshaft bearing speak for themselves. But suffice to say they didn't look like that the last time I saw them. Also, odly, there are no obvious corresponding marks on the journal of the camshaft. Was it the previously fitted camshaft that caused them? You may remember I swapped out a piper270, it's pictured further back in the thread, and is also free of the corresponding marks. Something nasty was in there at some stage. I wonder what the other bearings look like, including the mains. 1 view looks at the oil feed TO the camshaft, and the other FROM the camshaft. Both are completely clear.

Lawrence Slater

Well if the cam plate won't flip over to fit, that must have just been something I thought about, but didn't work. Pretty sure I didn't buy a new one. I think that tightening the sprocket onto the cam pulls the camshaft forwards against the back of that plate, but it is odd that there is only one thickness available. The wear on the three corners clearly isn't just from being tightened up. It is distortion from a hammering action - the metal has been deformed and flowed so the plate must have been vibrating or rattling relative to the block. Maybe not tight enough? I would have used locktight on those little bolts. I see you have a flat washer under one and apparently nothing under the other? Maybe just popped together again for the photo?

Guy

Excellent report. I'd only add that the crank would also be squirting oil - and presume it would and add to the fill issue.I'm surprised by the relative heights of the casting drain hole V the opening in the canister - maybe you could double check that. If it's true that's a design howler of epic foolishness.

F Pollock

Nasty! Just occurs to me that the elongated oil hole in the bearing isn't as I thought just to allow for different alignment positions when the bearing is fitted. It measures out the size of the glob of oil that then transfers into the grooves in the rotating camshaft. There is then a double squirt process. One groove collects its supply of oil and then delivers it round to the other hole and injects it up to the rockers. The second slot comes around, fills with oil and squirts it out of the front when it aligns with the hole in the plate. In practice, at 3000 rpm it would be a continuous but measured process. What is the notch in the end of the bearing for? Does that align with the hole in the plate?

Guy

Overflow, breather, and drain. The drain holes were completely unobstructed, although their positioning behind the crank sprocket and chain can’t exactly aid drainage. The size difference between the breather hole and the overflow hole( -- breather area is about .89 sqin, overflow area is about 0.25 sqin –if my sums are right ), and their heights with respect to each other(picture follows), shows that the overflow hole must be completely submerged in oil, even as the breather hole continues to fill.

Lawrence Slater

Guy, I've wondered about that notch, now you mention it, it, as the front groove aligns with it, an even bigger gap exists for oil to escape through. The notch sits at about 1:30ish on the clockface, and the endplate oil feed hole, sits at about 8:30ish. Fergus I agree, With the pressure of the mains, I wonder why it was considered necessary to add an additional oil feed to the chain. Or is the mains pressure at that point, very tightly regulated to ensure there is no pressure drop in the crank and the rest of the system? Heights of holes picture follows.

Lawrence Slater

"their heights with respect to each other(picture follows), shows that the overflow hole must be completely submerged in oil, even as the breather hole continues to fill." That must surely defeat the theory! Even squirting oil in under pressure, the level cannot possibly continue to rise much above the sill of the overflow hole. Its way too big and even cold viscous oil will pour through there. If the measurements are that way, then the only other thing is if the oil doesn't obey gravity because of the rotating cam chain. Await your photo, but I have got to go and do some work soon!

Guy

The base of the hole for the overflow, sits lower than the base of the hole for the breather. The overflow hole is also smaller than the breather hole. For the oil to be sucked into inlet manifold under a vacuum, the internal hole in the breather canister has to fill. This is in fact what happens, so the obvious implication is, that the smaller overflow hole, is submerged in oil, even as the oil level in the timing cover continues to rise, and the breather canister hole continues to fill. Not very good that. Edit, Guy just read your last comment. It's possible my logic is out. I'm google eyed. :) See what you think. Las pic to follow is of the mesh inside the canister. YES, strike the comments about the base heights of the holes. But there is an overlap, anyway they are too close to be a good idea as Fergus already pointed out.

Lawrence Slater

Wire mesh in the canister. Doesn't show much, one way or the other does it? I think it's there to catch particles, that would otherwise end up in the bores making pretty patterns. Edit. The sun's out and I'm going for a Subway and coffee. Let me know if want other pics of anything in particular.

Lawrence Slater

Last comment a'fore I go out. The breather hole must fill, else the oil suck wouldn't happen. This is the case, irrespective of the placement or size of the overflow hole. So something, either churn from the chain, backpressure from the cranckase, suction from the breather, the thickness of the oil, the close proximity of the crank front paddles flying round resiting the flow of oil back into the crankcase, or the almighty hisself, stops sufficient oil flow back into the crankcase, whilst the breather hole continues to fill. And here's another thought. That "overflow hole" was considered to be a splash feed to the timing chain cover. If the crank paddles are flinging oil through there as well, ------------! I rest my case.

Lawrence Slater

Thanks Lawrence it all makes interesting reading and now the AHC site has a thread on this! It appears there was a problem with oil suck but this time related to a PCV. A good clean sorted it out apparently which suggests suction was too high! BTW I believe the cam plate is handed as one face is white metalled. If you look on the edge of it you can see the two different metals. The initial wear marks occur quite quickly in my experience and then settle down.

Bob Beaumont

Yup Bob. That was my reading too. I put the dull face against the camshaft face, because it looks like the white metal you describe. Back later, I'm starving.

Lawrence Slater

I think I may have tried flipping the cam plate and then discovered it wouldn't go! It was a long time ago. I wouldn't be overly concerned about the cam plate wear marks where the cam turns - that is just normal wear and I suspect Bob is right - it happens quite quickly, and then settles down. The hammered/ distorted ends where there shouldn't be any relative movement looks to be more of an issue to me. If the overflow is only 3/16 lower then maybe it doesn't drain fast enough, even though lower. And you haven't listed cornering forces in your list of contributing factors. A quick wizz arrond a roundabout could provide the necessary to lift the oil over the offending oily orifice! I thought a subway was one of those footpath passages under a road network. Where shady characters hang out. But maybe that's right then. Or are you a busker?

Guy

I am under the impression that the wire/plastic gauze in the breather cannister is to prevent items from being drawn into the engine. That front cam bearing has had something pretty horrid go through it - I haven't seen one that scored before. As previously mentioned the cam retaining plate is handed and white metalled one side.

James Bilsland

Guy, Spicy Italian meat in a 6" roll with salad, and a coffee, for 3 quid, from the Subway fast food. :) OK, going back to the hole heights issue, see my pic. Scuse my scribble. Now my brain is clear again I'll restate the issue. The base of the overflow hole sit's HIGHER, than the bottom of breather hole by 3/16". But it's top sits lower than the top of the breather hole by 5/16". So it pretty well sit's in the middle. Guy, the point I'm making about the wear grooves in the cam end plate, is that they provide additional space for the oil to escape into the timing cover. I'm not so worried about the wear per se. Although, my pictures haven't really captured the wear well. It's much worse in the flesh so to speak. Also, if you look at the 3 holes in the cam plate, you can see each is lined with a steel sleeve. The sleeves sit proud of the bearing face, and in effect stop the bearing sitting as close to the cam face as it should. Again, it's only because I keep looking that I'm seeing these things. James. Yeah, the bearing does look rough, but the shaft journal looks perfectly ok. I can't think how.

Lawrence Slater

And here is another thought that struck me. We are calling it the overflow hole now, but maybe that is not it's intended purpose at all. Sump pressure is relieved via timing case as we know. The only way for that pressure to escape from the sump, if not through the rear scroll, is through this "overflow” hole, and into the timing cover. The only other openings are the 2 small oil drain holes in the front main cap. So the engine was designed to relieve sump pressure, but was it actually intended that the “pressure relief” hole, aka the “overflow” hole, should perform dual functions, and possibly triple functions, if you consider it as a “oil splash feed” hole too? This seems pretty unlikely to me. Pressure and oil splash going in one direction, whilst oil flow is trying to drain in the reverse direction, at the same time. A pressure relief hole would make sense located at that height. Well above the oil reservoir in the sump, and in theory well above the level of oil in the timing cover too. ------------- Unless the timing cover fills with oil of course. Maybe that possibility was over looked. Maybe it just wasn’t thought about, and no designed overflow hole exists. Have you ever seen anywhere except here in this discussion or bbs, where that hole is called the ”timing cover oil overflow hole”, or similar? I haven’t. Thoughts?

Lawrence Slater

So a subway is a sausage roll with salad? Not heard them called that before. Yes, I got the point about the wear grooved in the cam plate (and in the cam bearings) increasing the oil flow rate, and this is significant to your blue smoke problem. But I still think that the hammering action is odd. I thought that the little raised rims around the bolt holes were caused by the same hammering action, deforming the steel into the mouths of the 3 bolt holes. Are you sure that they are steel liners to the holes, not deformed edges?

Guy

Sub is I think short for submarine. Its a roll that looks like a submarine. American idea no doubt. :) And the chain is called Subway. Very nice as it happens, and all kinds of fillings. I'll see if I can dig one of the sleeves out of the plate. It is definitely seperate to the bearing surface. It may be an extention of the steel on the reverse side. We posted at the same time guy. What do you think to my latest thoughts on the so called overflow hole?

Lawrence Slater

Agree. We have been calling it an overflow hole but in reality the system is surely never expected to fill the chainchest with oil like that. It may act as an overflow when other things go wrong, but it isn't its proper design function. Its a bit like saying that the square front to the sump isn't much good as a snow plough when that isn't its proper design function!

Guy

In which case Guy, this is an amazing oversight/cockup in the design, and I'll be amazed if nobody ever worked it out before. There MUST be notes on this somewhere. Mustn't there? Well, -------- How about this for a way to resolve the oil suck issue easily and very cheaply? Currently, engine venting flows in through the mesh interior of the rocker cover cap, down through the engine to the crankcase and sump, out via the “overflow” hole, aka, the “crankcase pressure relief ” hole, via the timing cover, up through the breather canister, and into the connection on the carbs or manifold. Why not reverse the flow? Down through the breather canister on the timing cover, into the crankcase and sump via the overflow hole, up through the engine, out through a pipe on the rocker cover, and into the carbs or manifold? This would make it impossible for oil to get sucked into the inlet, irrespective of how high the oil level gets to in the timing cover, irrespective of how much oil is being pumped by the camshaft endplate, irrespective of how cold or hot the engine or the day is. Doing this, the hole in the front face of the block could properly serve 2 purposes. It would be a positively assisted overflow hole, if and when the timing cover oil rises to that level. And for the rest of the time it would simply be a passage for clean air from the exterior of the engine, to vent the crankcase. All that’s needed, is an air filter on the now open timing cover canister, and a rocker cover with a pipe on it, leading to the y piece or single connection on an HIF44. I can only think of 3 possible problems. 1) If the rocker cover filled with oil. This could be a problem when filling/topping up with oil when running. But there already are engines with breather pipes in the rocker cover, that lead to the air filter, so it shouldn’t be a problem. 2) Would the reverse flow of venting air prevent rocker cover oil draining to the cam followers, and back to the sump? I don’t know. Would it? 3) Would the reverse flow of venting air, cause the oil to drain too quickly from the timing cover? It would still drain in the normal way via the 2 small holes in the main cap, but the potential exists for the oil to be sucked off the chain. However the chain would still be getting a fresh supply from the small “reservoir” at the bottom of the timing cover, and constantly via the camshaft endplate oil feed. So it seems unlikely.

Lawrence Slater

Sounds OK to me! The only thing I think you haven't covered is what I believe to be the function of the canister device. It must have a purpose, otherwise why not just have a simple 1/2" hose connection on the front? I think that the canister, fitted externally to the hot engine and in the direct air flow from the fan, is designed to cool and therefore condense the oil out of the vapour as it is being drawn through the wire mesh stuff. If you design a system that reverses the whole direction of flow, then in the absence of a condensing canister it would need to be plumbed via a catch tank system. But the real truth is that your engine is faulty. Or at least if not faulty, then at one extreme end of what it is designed to cope with. Maybe the design should have had more built-in tolerance.

Guy

IMHO... You need to make sure you aren't re-inventing the wheel here - The timing chain cover drain holes are the two small holes in the front main bearing cap The hole in the front of the block is a casting hole and also acts to allow the positive crankcase pressure to escape into the front cover and thence out of the breather cannister (small block A series didn't have a front timing chain cover breather) A-Series engines are not designed to gather a large quantity of oil in the timing chain cover and in most engines they don't - on the rare occasions when they do it clearly causes the problem described above... Having seen the damage to Lawrence's cam bearing I can see how it happens on this particular engine FWIW My understanding is that the ventilated rocker cover cap allows pressure to escape, not air to enter into the engine... internal combustion piston engines are air pumps - the air comes in via the induction - pressure is multiplied by combustion - positive crankcase pressure is caused by air and gases pushing past the rings and by the bottom of the pistons moving up and down - pressure is positive throughout the inside of the block and head - it does not flow through the inside of the engine (the block and head are linked via the pushrod holes). The greater the combustion pressure (i.e. a tuned or forced induction engine) the gretaer the positive pressure and the more engine breathing required. Older engines also breath more because the rings are worn and therefore less good at sealing the pressure into the combustion chamber HTH James

James B

Guy - I agree - the front canister is designed to condense oil out of the positively pressured vapour so that it runs back into the engine. Small block A series and Cooper S engines had a similar canister attached to the tappet chest covers

James B

James, I agree your approach, but I believe that on the 1275 the system is designed to actively draw air out to exhaust the excess blow-by past the rings. Not simply to breathe to atmosphere, but to create a negative pressure in the crankcase, or at least to minimise the pressure there in order to reduce oil being forced out past the rear crank spiral "seal" system. In this, the design differs from the original early A series design which simply passively vented via the rocker and tappet covers.

Guy

Guy - accepted that attaching the oil breather to the induction side will create a negative pressure - I tend to doubt however that it is ever sufficient to overcome the positive crankcase pressure, maybe in a brand new standard 1275...

James B

Guy, James, my engine exhibited this problem from new build. That seems to keep being forgotten. Bobs recently built engine has the same problem, and even Fergus has had it. So there has to be a cause other than wear. That’s what I have been trying to find out for over 25 years. So what was/is the fault? One thing I know. Whatever the design intentions, a)nothing is ever perfect, and b) unexpected consequences can't be designed out of a new system before they arise. You can think you have covered all eventualities, but the unknowable, is just that. That's why designs are subsequently modified, as the A series was. Example? The later timing cover Fergus put up. Agreed the oil was never intended or expected to rise to the level of the hole in the block face -- whatever it's purpose. But the fact remains that on some engines it does. Can anyone say with any certainty, what level the oil reaches in the timing cover of the average A series, when it’s not exhibiting these symptoms? There is no way to measure it. Is there? That’s another thing I wanted to do. Is there a flow rate diagram that measures the amount of oil delivered by the camshaft endplate, at different engine speeds and temperature conditions? Is there a matching one measuring the rate of flow through the 2 drains? I have no doubt that these measurements must have at least been guessed at or estimated. But the unexpected happens, and it appears in this case, that it was not planned for, precisely because it wasn’t anticipated. Guy, James, apart from knowing that it's below the level of the top of the canister internal hole, (evidenced by the lack of oil being sucked into the inlet manifold on your engines), do you know the oil level in your timing cover? How do you know that it is not often, or occasionally, reaching that 9/16" hole, and flowing through it back into the crankcase? I’m not reinventing the wheel, as much as seeking perhaps to alter it, to cope with a condition that wasn’t anticipated when it was invented. My engine. I wasn’t expecting to find my cam plate in that condition, or the bearings quite so buggered. I was expecting to find excess endfloat, possibly a recessed front cam bearing, and a possible a worn front bearing. I expected these as there is no other explanation for why the oil rises to such a high level? I found 2 definately in the form of end float and wear. They were new once. I re-used the cam plate, but so has Guy, and he hasn't got this problem. If it is design tolerances, then clearly on my engine at least, and maybe Bobs too, the wheel has to be re-in – vented. : )

Lawrence Slater

James - I agree, the system may not actually achieve a negative pressure, or not for long anyway - that's why I added "or at least to minimise the pressure". But I believe that is the direction that the design was evolving. They were after all dealing with a design already some 20+ years old which had been stretched nearly to its limits as far as normal production for the general public was concerned. What may have been fine on an 803cc version at low compression, low revs and low power clearly wasn't going to work the same by the time it was a developed 1275. Lawrence you ask a lot of questions about measurements and what is known in real life circumstances. Just the sort of thing I would presume that the designers and test-bed engineers were looking at in 1965. You and I may not have the answers, but I am sure they did. And they came up with the solution that works for most engines most of the time. They may well have been aware of the limitations but accepted that for the few million production specification engines, that the design was acceptable. If you need to improve on it for your engine, which is after all not in the state of tune that BMC manufactured and sold their engines, then I would be interested to know how you get on. It certainly won't be the first aftermarket breather system to be designed for the A series!

Guy

Lawrence Just as a thought, how about using a non-breather timing chain cover and taking your breather pipe from a point on the top of the rocker cover (a common place for a breather on race engines - rocker covers do not fill completely with oil) - if you have a mechanical fuel pump blanking plate on the block you could if necessary fabricate a further breather to that (although accepted some 1275 blocks don't have the plate)... JB

James B

"--- your engine, which is after all not in the state of tune that BMC manufactured and sold their engines,series ---" I know Guy, and neither is yours, and yours doesn't suck oil. Why does mine, and Bobs, and yours not? I don't have any desire to modify the design at all really. I just want to know for certain that when I put it back together again, it doesn't suck oil. I don't have completete confidence, that replacing the end plate and cam bearings, and lowering the oil pressure is going to prevent it happening again. To me the solution is preventing the oil reaching such a critical level. Everything else is to ignore the problem. I guess I'm fussy like that. Truly, I'm a bit of a perfectionist about some things, and this thing has got my goat, that's for sure.

Lawrence Slater

Hi James, I've thought of using the fuel blank before. Laziness and a solid block have stopped that thought going any further. But you mention it, just as I was sitting here thinking about it again, prompted by the comment you made about the side cover breather on the sub 1275s. If get hold of a canister and fix it to a plate, drill into the blank, and then bolt it to the hole on the engine, with a pipe straight to the HIF connection, that should provide just the same suction on the crankcase. Is that right? Timing cover is easy as temp fix. Just plug it.

Lawrence Slater

Simple answer? - 'cos your engine sucks. Seriously, I think you have already identified too many variables to be able to pin point exactly why yours does this but others (mine included) don't. All you can do it seems is either something to lower the oil level in the chaincase as it was intended, or modify the breather system. How about some sort of poppet valve in the canister so that if the inlet begins to suck oil it opens and breaks the vacuum. Presumably once the canister inlet is submerged in oil the vacuum level in the canister and pipe must rocket - it can no longer draw in air - so a lightly spring loaded valve would do it. How about a hole in the canister that is normally sealed by a flap of rubber, which opens when the vacuum rises too high? May not be controllable enough. Adding a T piece to the hose with an adjustable valve of some sort in the side branch could be quite neat and easy to install!

Guy

lol. Sucks? That's an Americanism Guy, can you use that in Cumbria and get away with it? So in other words add the fail-safe that BMC didn't know was needed. Yup I agree that would be an idea too. I could use the old PCV valve, if I had one still. But you're right, and inline normally open valve that closes on or very near vacuum. They must be pretty freely available I would think. I'll start googling that.:)

Lawrence Slater

I was also thinking at the other end of the problem. The begining. Stop the oil feed, and feed it from somewhere else, with a device to sense the level. I was going to ask Prop to come up with something. But he seems to be ignoring this one, as do most here. I think I must be boring people. :)

Lawrence Slater

Actually, how about this? A device that floats in oil, and when it reaches the top of the canister, it blocks it. The oil level falls and goes back to normal. Comment?

Lawrence Slater

Not boring at all, just a lot to digest ;) BTW I have the second breather / cannister option on the blanking plate. No leaks from rear seal, no blue clouds. Did have some, but that was due to normal guide wear and multi-particle piston rings before rebuild.

Alex G Matla

Hi Lawrence, I think you have misunderstood my suggested modification. It isn't a valve normally open that then closes to shut off the oil surge. It is a small air valve normally shut, that is spring loaded such that if the vacuum level in the canister or hose to the carbs suddenly increases, the valve opens, lets air in and breaks the suction on the column of oil, allowing it to drain back into the chaincase. Once oil is at a level to fill the entrance to the canister, the system can no longer draw air through and the vacuum level must rise rapidly. At that point a release of air into it will break the vacuum and stop the oil surge. A simple T piece let into the hose and fitted with a small automatic air valve, preferably adjustable,would be a neat solution. I am sure something could be made adapting a schrader tyre valve.

Guy

Hi Alex. Glad you're not bored then :) Could you post a picture of your breather canister setup? Did you blank the one on the timing cover, or link that in as well. I would imagine they would fight eachother, so I'm assuming you blanked the timing cover vent off. Hi Guy. Wouldn't that present a sudden air leak to the inlet on the carb? Or do you mean a dual action valve, -- one that opens free air to the canister, but closes off the pipe to the carb/manifold connection?

Lawrence Slater

No, just a simple air valve. Spring loaded it would open when the vacuum gets too great, and break the suction on the oil column allowing it to drain back into the chaincase. Yes it would weaken the mixture at the carbs, but it only needs to be for a moment. Spring loaded, as soon as the oil has dropped out of the cannister it would snap shut again and reseal the intake. It shouldn't have really any more effect than drawing air/ fumes into the intake in normal running. It would be easy to make one - 1/2" copper T piece fixed in the hose and with a tyre valve set into the side branch. I would think that the inside mushroom end of a tubeless tyre valve stem would probably be a good tight fit into a Yorkshire fitting, with a bit of sealer around it. The spring in the valve might need adjusting but they don't are pretty light springs and may be about right just as they are.

Guy

Just to add the vented oil filler cap is designed to breathe both ways. Normally air is drawn in to circulate and be sucked out to the manifold, but when the mushroom PCV closes,the blowby pressure is meant to exit through the gauze in the cap. That's why putting a shiny chrome one on with a tiny hole inhibits this function, and can contribute to leaks at the scroll. The PCV system of either persuasion only 'copes' on a basically standard engine in good nick. Once the C/R rises with compressions above (I think) the 200 lbs mark or you run wide ring gaps blowby increases (much worse on forced induction engines) and any negative suction is simply overwhelmed and the positive takes over.I think controlling the amount of oil in the timing case on modified engines may be helped in a few ways. Firstly reducing the quantity of oil fed from the cam plate - by flush fitting/hole size reduction, and also modifying the cam splash ring so it sits tighter to the cam gear. Dropping the casting hole and raising t'other to the max possibe can only serve for the good.

F Pollock

Thats interesting, I am running about 11:1 on my new Slark head up from the original 9.75:1. its reasonable to assume that the crankcase pressure is higher and possibly positive. It is certainly airtight as the revs drop on idle when the oil cap is removed and the mixture is weakened which would suggest its still negative. I will check if there is any 'suck' when I remove the cap.There is no evidence however of any oil mist around the cap, although I have noticed some around the front damper pulley.

Bob Beaumont

Eureka! Hi Fergus. "---reducing the quantity of oil fed from the cam plate --". Very opportune comments I might say. I've just come back in from my garage, where for the last little while, I have been looking at a few things, because certain thoughts wouldn't rest. James said. "If the timing chain cover was running that deep in oil, why would you design into the engine the thrower ring on the crank chain gear end." We all agree on that, and my reply was, there is a fault(s). Now I believe I've found them all. Oil has been leaking from a faulty gasket, a poorly fitting camshaft end plate, too much camshaft end float, and above tolerance wear/damage in the front camshaft bearing/journal combination. These are the missing factors. With the gasket being the hidden joker in the pack. Oil feed via a leaky tap, a gasket, excess end float, and wear. The small hole in the camshaft end plate, along with the front facing groove in the front camshaft journal, forms a tap. It's designed to release a measured amount of oil to the timing chain and sprockets. That tap is turned on once in every revolution of the camshaft. A tap only works to stop flow, if the intended outlet, is the only outlet. If there's a leak before the tap, the tap can't control that leak induced flow. The engine front plate. The engine front plate bolts to the engine block, and in between is a gasket. That gasket stops engine oil (from the timing cover) leaking to the outside via the rear of the front plate. HOWEVER. It ALSO stops oil under pressure, leaking into the timing cover. -------- But only if the gasket is in good condition. Mine isn’t, and oil has been escaping from behind the engine front plate directly into the timing cover. The camshaft endplate. The camshaft endplate bolts to the face of the engine front plate. Oil isn’t supposed to leak from behind the plate. It’s supposed to flow through the small hole. Controlled end float prevents excess oil seeping through the large hole in the camshaft end plate. My end float is excessive, and there is above tolerance wear in the front bearing/journal combination. Additionally, my end plate is also slightly distorted, and does not sit completely flat on the engine front plate. Hence, oil has been escaping continuously into the timing cover. As it should be Small amounts of oil must come from the front mains cap, but this must be limited. Small amount of oil come from the large hole in the camshaft endplate, due to end float, but this is limited if the end float is not excessive, and camshaft bearing wear is within tolerance. No oil is supposed to leak via the rear of the camshaft endplate, or the rear of the engine front plate. I now think that those 2 extra supplies of oil filling the timing cover as soon as the engine is started are the missing factor. Fix those and there wont be a need for me to modify the breather system. How this looks on other engines that develop this fault, can only be seen by stripping off the front of the engine and taking a look..

Lawrence Slater

Bob - the simple way to check it's negative is to hold a piece of paper over the open filler neck. If it's negative the paper will be drawn down tight, with higher overlap cams it usually vibrates but essentially remains pulled down, and if positive it simply tries to blow it off. I'm assuming a nominal idle speed here around 950 rpm.

F Pollock

Thanks Laurence Useful diagnosis, but if all these things are happening then why do we get the problem at warm up stage only? Surely all this extra oil will be coming in to the timing cover all the time? or is it that as the oil warms and thins it can escape back to the sump more easily?

Bob Beaumont

Lawrence, Did you discover why your cam plate has the three raised collars around the bolt holes? Don't they prevent it bolting up flat against the end of the cam? Or are there corresponding countersinks around the bolt holes? Maybe they are there to accurately align the plate so that the oil squirt hole is positioned properly.

Guy

Lawrence, no pic at the moment, car is in the shop for a new rear. But I have both cannister hosed in to the carbs, each one.

Alex G Matla

OK, thanks Alex. Hope the car gets sorted quickly. When you can get the pic I'd appreciate it, as I can't even find the timing cover with the vent for sale anymore, and wonder which canister you used on the fuel blank. Guy, 2 possibilities. The cam end plate is a laminate. Hard steel on the rear, and white metal as the bearing surface on the thrust facing side (camshaft). The steel extends through the bolt holes to the thrust side to form sleeves. The diameter of these sleeves is less than that of the engine front plate holes. Explanation 1). As the cam end plate has been clamped to the engine front plate, so it has compressed the softer white metal and effectively raised the level of the sleeves. Certainly for a long time, 25+ years, that’s been the case. Explanation 2). I'm intrigued with odd triangle marks on the cam end plate. This engine(spare) didn't come with the car when I got it, I acquired it later, and it had been apart before. I took it apart and reused some bits in the rebuild. One of which was the cam end plate. Now you have to remember these are 25+ year old memories. However I seem to recall now, after much thought, that when I took it apart, the cam end plate was bolted to the engine plate, with triangular washers, and was fitted with the steel face to the camshaft. I've checked it fits this way, and displaces the oil feed hole by some x degrees. There is evidence of this. There is a very faint wear ring, that appears to match the diameter of the camshaft thrust face. But the bearing as it contacts the camshaft face was smooth and seemingly unused. Tight wad that I was/am, I must have flipped it over to the correct side, discarded the triangles, and thought no more about it. The wear marks you see now wouldn’t have been there, or even I would have binned it. Anyway, looking more closely this afternoon, I find that because the cam end plate is in such poor condition, it is possible to bolt it up, thrust facing the camshaft, with the extended sleeves preventing the cam plate sitting right up against the engine plate. I wasn’t expecting this as I disassembled it, so didn’t notice how exactly it was sitting. But, add to this the slight distortion in the cam end plate, and it explains a lot. Bob The reason remains the same. Although the oil is flowing in excess, it still takes a while to fill the timing cover. At the critical point, the vacuum takes over. The engine continues to warm, the oil although thinner, is under slightly less pressure, and eventually thins to the extent that the “overflow” takes all the excess, and the drain holes come into their own too, exactly as you said. I doubt all of this will apply to your engine. I doubt you will have cam end plate like mine. But for whatever reason there must also be an explanation to why yours fills the timing cover to the extent that vacuum can take the oil to the inlet manifold. All Even more interesting, well to me anyway. The engine front plate, is a laminate as well. Soft metal on one side, and hard steel the other. The hard side faces the engine. Why would it be made like this? It doesn't provide a bearing service, and the back plate isn't a laminate. Any ideas on that?

Lawrence Slater

Lawrence, Why do you think the engine front plate is a laminate?

David Billington

Hi Bill, I noticed it when I was wiping the grime off the edges, particularly on the edge of the cut holes for the camshaft, main shaft, and the block opening hole. You can clearly see the 2 different types of metal, delineated with a clear and sharp line. Exactly like the camshaft end plate. As a test, I scratched both the engine side of the plate, and timing cover side. One side, timing side, scores very easily, and the rear not so. It extends over the whole of the front face of the front engine plate, even to the engine mounting holes. Very odd I thought. It appears to be a fairly precise component, in the sense that is has such a very well finished surface on the timing side, and although still smooth, a rougher surface on the engine side. Rather more than just an end plate. I’ll try and capture it in a picture, and post it later.

Lawrence Slater

Ps to this. In the caverns of my memories, I seem to hear the echo of something I read somewhere, that you are supposed to replace the front engine plate when carrying out a full engine rebuild. But that would be pretty hard, as it's not a seperately listed part. It comes with the block I think, as it is listed as NLS. Part number 12G1309 on the 1275 engine.

Lawrence Slater

Could it be cooling? Might the dissimilar metals used in the front plate, aid the cooling of the engine? The harder steel absorbing the heat, and the softer metal, unknown, dissipating it more easily.

Lawrence Slater

Something to do with linking two different metals with different heat / expansion properties? CI block on on side, pressed steel chaincover on the other.

Guy

Lawrence, If you're looking at the edge of the plate and seeing this then I suspect all you are seeing is the standard type of edge finish left when the part was sheared/punched in production. This is the sort of thing http://images.discountsteel.com/files/image/oms_product/MEDIUM/Sheared_Edge.jpg and some more detail http://www.custompartnet.com/wu/images/sheet-metal/shearing-edge.png I can't think of any reason why BMC would go to the expense of a laminate for the front plate. IIRC the backplate won't show this feature as it's cast.

David Billington

David, That's comforting! I wondered why it was I had been so unobservant not to notice this bi-metal construction! And then I had to start inventing reasons to explain it! LOL!

Guy

Bill, Those images clear up something for me. I was wondering about the purpose of the rounded edges of the cutouts. Now I understand they were punched, and I am seeing the "rollover" from the cutter, it makes sense. However, I still believe it is a laminate. The surface of the rear, is definitely harder then the surface of the front face of the plate, which is very easy to score. Could the surface be coloured and softened by constant bathing in hot engine oil? The colour of the front surface, more resembles that of the bearing surface of an end shell when it's been in use, than of it's backing, which resembles the rear surface of the engine plate. I'll get a picture tomorrow and show you. Guy, the valve idea sounds good. It got me thinking about how to detect this sucking as it happens, other than observing a cloud of blue smoke. One way would be to connect the regular vacuum gauge to a T at the connection on the carb. As you say the vacuum would rise suddenly. This led me to think of a visual or an audible warning. A buzzer or lamp. And if that works, then why not an electrically controlled vacuum release valve, that can be varied by a control on the dash.

Lawrence Slater

Yes, in theory you could devise something with a control operable from the dash. But to me a more satisfactory solution would be something that is automatic and just works quietly in the background. I wouldn't want to be having to deal with monitoring and switching a system off and on when I want to be driving. But then I don't have the problem anyway. My suspicion is that if you just reassembled with a fresh new cam plate and check the cam end-float is within limits, you would solve the problem anyway. At least that would be my start point.

Guy

Guy, I wasn't thinking of the vacuum detection device as a permanent feature. It's something I was thinking of as a diagnostic, so you could detect the moment it happens, and maybe use the information to work out why. But also so you could fine tune it, in case it fired early because it was too sensitive. Or maybe I'm becoming a gadget freak. lol. Otherwise I've already come to the same conclusion as you. I'm going to rectify the problems I've found, as I reckon it's going to fix it anyway. Crossed fingers and toes. One thing I might do though when the block is stripped, is drill the fuel blank, in anticipation of using it as the take off point for the breather, should I still experience problems. You can still buy the pump blanks to bolt over the holes I'd make, which I'd then leave in place even if I didn't use the breather. Or to save money I'd just make a blank. I've still got the gaskets left over from gasket sets of long ago.

Lawrence Slater

Laminate or not? It looks like it is to me, and even if not, why the different surface preparation? -- (I'm coming to that ). The front face is softer than the rear face.

Lawrence Slater

Lawrence, While the front and back faces look a different colour in the image the edge shot doesn't, taking into account the bits that still look dirty. The front back difference maybe down to the surface finish. I seem to recall the face that goes against the block is ground and is the one shown so in your image, I would presume that's to make sure the face against the block is flat with no local distortion or burrs that may have resulted from punching the piece out. The front face not being so critical as it has the relatively flexible pressed steel timing housing against it.

David Billington

If you drill a through a frontplate, and it would be laminated, one would notice this. Different curls from the drillbit, differen feel etc. It doesn't. It is what it looks like; a piece of sheet metal.

Alex G Matla

Sorry David, I called you bill, don't know where I got that. Anyway, yep the edge does appear the same colour there. That's because I cleaned that whole edge to get a decent picture. I'm still unconvinced about it being the same material both sides though. If you saw it for real, instead of my less than adequate lighting and photo technique, you'd agree. I'll take it down to my local engineering metal works, so they can take a butchers with their eyes, in the flesh. Anyway, be it laminate or not, which doesn't matter I guess(or might do), I take a different view regarding the surface finishes. The rear and front faces both have gaskets for the purpose you describe. And my rear gasket was leaking. However there is very important reason for the far smoother finish on the front face side, without the grinding marks of the rear face. The front face has to be a half decent surface for the camshaft end plate to mate against. If it didn't, oil wouldn’t need the small hole in the end plate to feed the timing chain, it would seep from under the edges of the end plate, as there is no gasket there to seal it. Because of the bad state of my camshaft end plate, that is exactly what was happening, as you can see from this photo. Oil has been seeping/pressure fed, into the timing cover between the gaps where the rim of the camshaft end plate doesn't sit tight against the face of the engine plate. Previously, I put this solely down to the fact that the camshaft end plate is distorted. Which it is. However, I've now discovered, as I should have seen all along, the front face of the engine plate, where it mates to the camshaft endplate, although smooth, is not flat either. The combination of the two surfaces not being flat, has resulted in a 4 - 5 thou gap, around a great portion of the seal between the camshaft plate and the engine plate. I'll post a picture illustrating this in a following post. PS, that's a good idea alex, maybe I'll drill a small pilot hole.

Lawrence Slater

They both look like laminates to my untrained eye.

Lawrence Slater

Lawrence, I actually ment that as a statement. I drilled the plate for the duplex chain tensioner. And those are both shear marks. The white bearing metal layer is so thin you can hardly see it without eye-protheses

Alex G Matla

Ah,ok thanks Alex. Well anyway, the front face and the rear face of the engine plate were made to a different finish, and I reckon that's for the camshaft end plate. How likely is it, that over the course of at least 250/300 thousand miles, over at least 40 years, that hot engine oil, possibly laden with metal particles, could wear away, erode, the surface of steel? I ask because if my engine plate is not distorted for another reason, then is must have eroded. And under a magnifying glass, that is exactly what it looks like, in the regions where oil has been flowing between the camshaft end plate, and front face of the engine plate. All these engines are roughly the same age now. Some older still. You can't buy engine front plates new anymore. So if this has happened to mine, it might well be happening or already have happened to other engines too. Can the front plate be skimmed to make it flat again? Can it be skimmed between the upturned engine mounts? Anyway, here's a picture of the resultant gap, on one side of the triangle. The other sides are the same. Just in case it's not clear, this is a view from underneath the engine plate, with the camshaft endplate weighted down in place on the top, with light shone through the 4-5 thou gap. A lot of oil could flow through there.

Lawrence Slater

All the heat cycles could have had influence on the material, hardening it. And about the dirtortion, maybe the forces from the engein, transferred through the engine mounts did that? A good machine shop should be able to skim it both sides

Alex G Matla

Don't you mean softening it? The front face scratches easily compared to the rear face. Also, I can't see the engine mount forces doing this (distortion I mean), when it's been bolted solidly to the block. Also, the surface area that should be in contact with camshaft end plate, has moved back, if you like, relative to the camshaft. I.e towards the engine block. I can't see how it would do that. It must be worn away. Well as I won't be able to get new one, and as I now see what's wrong with mine, I don't think a 2nd hand one is worth it. So I guess a machine shop trip is coming up.

Lawrence Slater

Interesting Lawrence One thing i did change on the rebuild was the front engine plate! The old one cracked around the hole for the dynamo adjusting pin. Turns out I was using an early 1275 front plate the later ones, and the one I used, has a strenghthener at this point. I did not check for flattness of the front plate but did replace the cam bearing plate. I don't recall the smoke problem back then but I guess there could be wear which is exacerbating the oil flow. I am going to renew the oil cap and breather pipe tomorrow. Wil report back. After all this research I am not counting on a positive result now:(

Bob Beaumont

get the (vented/filtered black plastic) oil cap from somewhere like MGOC at around £4 rather than elsewhere at around £10 both are exactly the same - I know I got caught out by assumming prices would be about the same without checking

Nigel Atkins

Bob, You've just aged my spare engine then. Mine too has the strengtheners. I wasn't aware that from the later ones. I've just taken some closeups of the the front surface of the engine plate, where the cam plate sits. You can really see the wear in the corresponding areas I indicated on the cam plate a couple of posts back. Like fine pitting. I was just thinking about your engine. I was thinking that you can rule out the engine gasket. I didn't fit mine properly, or replace it. You probably did both. You are unlikely to have end float as you have a new cam plate, and your bearings are good. And now you've just mentioned the one thing I've just posted about. So we both have excess oil pressure, and you've just changed the engine plate, prior to which you don't recall the big blue suck. --- hard to miss. Is that the clincher then?

Lawrence Slater

Lawrence, I may have missed this but what has caused the triangular wear / deformation patches around the cam plate bolt holes? It looks like someone has used some sort of spacers there. Why? Maybe it was someone's attempt to move the camshaft forward so as to align the sprocket faces, instead of using the proper shimming arrangement. Apart from creating the excessive oil delivery, it has also distorted the cam plate, resulting in the three "high spot" wear patches from the cam journal.

Guy

Guy, scroll back to my post, 24 February 2012 at 19:32:07 UK time for the full text of that post But here is the bit about the triangular marks. I wrote. "I'm intrigued with odd triangle marks on the cam end plate. This engine(spare) didn't come with the car when I got it, I acquired it later, and it had been apart before. I took it apart and reused some bits in the rebuild. One of which was the cam end plate. Now you have to remember these are 25+ year old memories. However I seem to recall now, after much thought, that when I took it apart, the cam end plate was bolted to the engine plate, with triangular washers, and was fitted with the steel face to the camshaft. I've checked it fits this way, and displaces the oil feed hole by some x degrees. There is evidence of this. There is a very faint wear ring, that appears to match the diameter of the camshaft thrust face. But the bearing as it contacts the camshaft face was smooth and seemingly unused. Tight wad that I was/am, I must have flipped it over to the correct side, discarded the triangles, and thought no more about it. The wear marks you see now wouldn’t have been there, or even I would have binned it." The more I think about the more I Remember. Even from so long ago. I amaze myself that I can remember last year let alone the mid 80's. Anyway, all the pieces are coming together now. When I took it apart this week, I noticed the rounded edge on the engine plate, around the camshaft hole. I thought it was odd. What was it for? The other holes, though rounded, are still sharper. Now I understand about the shearing effect of the cutter, producing rounded edges, I can put it together. 25 years ago, I have a used engine, that already has high mileage and been built a couple of times. I have a bad camp plate, that's been fitted on backwards. I flip it and bolt it up. Tightening the bolts, pulls the the 3 points of the triangle onto the engine plate. But because the bearing surface has been compressed by the triangular washers, it pulls the points lower than the stretches in between. I don't notice that at the time. I have also re-used the engine gasket, rather than be bothered to scrape it off. It leaks but I don't know it. I get the engine in the car and start it, and then find I'm sucking oil. I take it apart, and think I see the problem with the recessed bearing. I don't then fully understand how the timing cover is fed with oil or all the other details that I do now. I blame the pistons, the rings, the 270 cam and the sun and moon, but can't fix it. I live with it. Eventually the engine needs to be swapped out. But in that 100 thou plus miles, the oil is being pushed in ever greater amounts through the gaps between the cam plate and the engine plate. The already rounded edges of the camshaft hole in the engine face plate, caused initially by the shearing force of the cutter, begin to erode. Hot particle laden oil under pressure. And so today, the gap between the cam plate and engine plate is probably twice what it was. Had I fitted a new cam plate way back then, it would have slowed that wear down. But the shearing force, creating rounded edges at the point, must act as a catalyst for wear, encouraging oil under pressure to push through. Had that hole been cut and not punched, there would have been a sharp edge, that would have sealed against the cam plate far more efficiently. Other engines might not have such high mileage. But I reckon that if you take a VERY close look at any front engine plate, you are going to see signs of erosion. So I think that posts of this nature are going to increase, as these engines age further, if of course they are used. And that's a point to keep in mind. Many of these engines have been left in cars not used for many ears, and so are still less worn in this respect. Others are only ever used in warm sunny weather at weekends. Hence, even if the problem lies lurking, the owner will never know, because they don't take lucinder or larry out in the cold.

Lawrence Slater

A point for the hp seekers. You take a 4 blade metal fan off because it robs hp. Some people say the same of the plastic fan, and replace it with a kenlow or equivalent. You might lighten and balance everything. You might fit lightweight timing gears, and you would expect that there isn't much drag from the small amount oil in the timing cover. If you have removed your front breather, you have no real idea how much oil is in the timing cover. Is it a dribble, distributed by the oil thrower, or a flow, churned by the timing chain and gears? You don't know because you can't measure it, and don't get oil sucked up the front breather to tell you about it, because it's been modified or closed off. I wonder what a car on an RR session would display in hp loss, if you got the engine running at a stable power output, and then poured cold engine oil down into the timing cover, sufficient to, 1/4, 1/2, 3/4 or 1/1 fill it? Some people say even 1 hp matters to give you an edge. You might be losing that and more in the oil in the timing cover, and never be aware of it. Doesn't matter on a road car, but, well I'm not a racer, so I don't know. Just a thought.

Lawrence Slater

Yes I recall that message, I was wanting you to confirm which way around the plate was fixed. This was the point "the bearing surface has been compressed by the triangular washers, it pulls the points lower" distorting the cam plate causing [irregular wear from he cam shaft and creating the gaps at the back which let the oil through. I am not really convinced about your thoughts on hot oil erosion of the front plate, but if that is what you observe, then I won't argue the point!

Guy

Lawrence, Any photo of the eroded area. I don't think it is eroded more likely distorted, possibly through over tightening, but if eroded by oil and particles I would expect evidence on the surface of the plate and I can't see any on the cam thrust plate photo you posted earlier in the zones marked as not bearing against the front engine plate.

David Billington

David, I know little about oil erosion of steel. But it sure looks that way to me. When I get to photoshop the pics ( for size), I'll post them. I don't know if I can show it as you look at under a magnifier, but I'll try. I also undeersatnd that the contents of used engine oil can be pretty corrosive. If combined with erosion, might that be a factor? I'm guessing, no more. Meanwhile, how could the engine plate, which is pretty thick, be distorted by the 3 thin bolts of the cam plate? If not erosion then, the distortion is recession of the surface of the front face of the engine plate, between the 3 points of the triangle formed by the cam plate. There is no force acting on the engine plate at those points. The only thing that was happening, was hot engine oil leaking between the engine plate and the cam plate. See my leaking light shot in the previous post. If wind and water can erode granite and concrete, I think it reasonable to condlude that hot engine oil under pressure, laden with metal and carbon particles, over the course of many years, and hundreds of thousands of miles worth of a revolving engine, might do something to the surface of soft steel. How else would you explain it?

Lawrence Slater

Here you go. I hope the combination picture speaks for itself. If not please question, and I will answer. I'll get the vernier on the engine plate at various points around the circumfrence tomorrow, to show the depth of recession between the bolt holes. I wish I had a digital jobby now, my eyes are finding it hard to read the scale on my regular one. I sometimes take a picture and blow it up to read it. lol. Wonderful invention digital cameras. Thank the lord, and praise be to the CCD. Otherwise, apart from another engine plate in my hands to make a comparison, I think this is done and dusted as far as cause(s) are concerned. What remains now, is rectification.

Lawrence Slater

Lawrence, In the image you've just shown I would expect that edge feature to be due to the proximity of the other large punched hole nearby resulting in less support to the plate and more localised deformation at the edge. I'd expect the same feature in the other, drain?, hole as well. Is the edge the same between the other 2 bolt holes about the cam hole.

David Billington

O/T Lawrence, how do you (without going to a web site for it) combine two photos into one please?

Nigel Atkins

Nigel see "For Nigel. Picture combining." In the general section please.

Lawrence Slater

Hi David. Of the 3 punched holes in the engine front plate, only the camshaft hole is recessed in this fashion. The other holes still have the same sharper edges as the section of the camshaft hole I've shown in the picture below. Yes there is similar degree of recession in the other 2 sections of the camshaft hole, coressponding to the same areas I indicated on the camshaft end plate, in the earlier picture. Everthing wears out. The camshaft end plate is a replaceable item. As there has been a distinct fault in mine, this has led to premature wear on the engine plate in the vicinity of the camshaft hole. Now I can see --- better than I can show here in limited size digital pictures -- the degree of wear on the engine plate, and now that I understand how oil enters the timing cover, I don't find it strange or surprising that the engine plate has been worn in this fashion. The engine plate is not mechanically distorted, it's simply recessed to some degree at those points illustrated in my pictures. That combined with the worn camshaft end plate, allows more oil to flow into the timing cover than should. It all turns out to be pretty simple, now I understand it. What might not be so simple is getting it skimmed between the upturned engine mounts, so I might need another engine plate. However, I need one with a minimal or zero degree of wear of the same kind. That may not be so simple. It would appear that Bobs' problem might coincide with an engine plate swap, suggesting that old engine plates, might all be worn to some degree in this fashion. How much wear of this kind is too much, is possibly impossible to predict. If all this is wrong, can someone please suggest how too much oil is being delivered to the timing cover?

Lawrence Slater

Update for whats it worth. renewed the oil cap and the breather pipe from the timing cover. The old oil cap looked ok but the new one did seem to 'breath' better than the old one.(Simple test by sucking and blowing through both!Nasty) The breather pipe was worn and had expanded and there was quite a bit of seepage from the joint with the cover and the pipe. Engine ran fine and no evidence of any oil problems but that is by no means confirmation its cured. There was negative pressure when the oil cap was removed at idle and this did not change from start up to normal running temeperature. i.e. paper was sucked into the rocker box when the oil cap was removed and the engine ran slightly lean. It therefore performed as expected. Interesting that this cap has to allow some air through it but not too much to make the engine run lean but not too little to create a vacuum in the engine. Will continue testing.

Bob Beaumont

Hi Bob, I did the same taste test as you did on the oil filler cap. Not pleasant lol. I've been given this yet more thought. If your pipe was a little leaky, that would let vacuum escape, and help to prevent the oil suction problem. However, lets suppose the oil cap you replaced, was blocked completely. If the cap was blocked, on the one hand it would increase the tendency to vacuum in the engine due to the breather system, but the pistons would counter that with the pumping James described earlier. So would this cause more oil to flow into the timing cover? Would there be enough suction to suck oil from the camshaft endplate? Would the blocked oil filler cap, aid or oppose the oil suction? Would the pistons suddenly cause a large increase in pressure because it has nowhere to escape to? Anyway, when the oil level did rise sufficiently to cover the breather hole, as previously described, there would be a sudden vacuum in the breather pipe to the y piece. At that point the oil is sucked up. However, behind the oil column, in the crankcase and the rest of the engine, there could either be a build up of +ve pressure, helping to push the oil up the pipe, or a partial vacuum theoretically opposing the oil suction, tending to resist the upward movement of oil in the breather pipe, and drag it back. If I hadn’t swapped my filler cap, and done the same tests you did, I’d have some confidence that a clean and new cap would fix the problem. However, not only did I swap my cap, but on my current engine, my oil filler cap must be at least at least 60 thousand miles old. Frankly I haven’t bothered to change mine for years and years. I’ve never found it to be blocked, and I don’t have oil sucking on this engine at the moment. I should change the cap for the sake of the engine oil I know, but I don’t think it’s going to fix the problem. Though I hope it does. I really do. Another reason I don’t think it will solve the problem, is because apart from you (Fergus too), nobody had even heard of this, and you can bet that over the last 40 plus years that somebody has been driving around with a blocked oil filler cap. If it had caused oil sucking it would be known about, and Nigel would be telling everybody why the oil filler cap must be replaced at the next 12000 mile service. Anyway, unless we get some winter weather again, you might not see the problem again until late autumn. That was how it was for me. Mild or warm winter day, no problem. Spring and summer no problem. Come a decently cold day though, and the blue cloud was back.

Lawrence Slater

Here's an update. Today I got a look at another engine front plate. Judging by the caked on oil sludge within the timing cover area, it appears not to have been running a breather, --- I would guess, or it was starved of oil changes, or both. anyway, once wiped away it looked thoroughly unmolested. Compared to mine, the hole around the camshaft was visibly "sharper", around the entire circumference, albeit with what I now understand is the classic rolled edge from a punch cutter. There was a uniform outline of the cam plate, and did not appear to show signs of oil being pushed under the cam plate. -- i.e. no flow marks or the like. It mostly illustrated the poorer condition of mine re the camshaft punched hole edges. I also saw a factory original cam plate, that was uniformly worn by the thrust of the camshaft. Again a distinct contrast to mine, but with a perhaps embarrassing (for me) but nonetheless interesting feature. (Never rely on 25+year old memories, and attempt to fit them accurately into a theory, without some supporting evidence.) Guy, going back to the triangular marks on the cam plate. The cam plate I saw today had the same marks, although not as pronounced, immediately visible. I also learned today, not sure if accurate, that the cam plate has dual thrust faces. One for the camshaft, and one for the sprocket. The predominant thrust is the camshaft, but if it has two bearing surfaces, which way round does it fit? I'm not convinced that it does have dual bearing surfaces and think the softer face is the camshaft face, which is pushed out of the block by the action of turning the distributor shaft. Anyway I absolutely remember the cam plate on my engine being mounted the reverse of how I later re-fitted it. But did my memory invent the triangular washers, remembering only the shapes of the indents, and inventing washers in my memories, to explain them? How can this other cam plate have the same marks? The engine plates are both completely flat at the bolt hole, so did not imprint the cam plates. The shape of the imprints are not curved on the long side of the triangle, but appear straight, and don't particularly follow the shape of the rolled edges of the punched hole in the engine plate. (Although looking at mine again, it could be interpreted as trying to ). One other curious feature of this original, but well used cam plate, is that whilst two of the "washer" like imprints are triangular, the 3rd is square. I'll post a picture later. Back to the engine plate. I took my engine plate to two separate precision engineering companies, with a view to skimming. It wasnt possible because neither had the type of machine that would leave a polished surface, rather it would be a lined surface. So no go. Anyway, the first said the front face appeared as if it had been blasted with fine media or the like, as an explanation for why it was different to the rear obviously ground face. He instantly saw that the camshaft punched hole, looked more rounded at the edges than the other holes, and that it was most prominent between the bolt holes. But couldnt explain it. The second agreed about the possible fine bead blasting for the surface, but added that the very obvious rounding of the camshaft holes, looked as if someone had deliberately rounded them further between the bolt holes, but unevenly. I told him what I thought and he said that could well explain it, as the surface is soften than it looks. Btw, the other engine plate had a similar if not the same front face surface, suggesting that this is how they came from the factory, unless both have been blasted subsequently by owners. From the first engineers I acquired 4x4x2 lump of bright steel, very flat and polished on the surface. When I got home, I used this with some 280 paper and water, and began a test grind and polish, on the front surface of the engine plate, across the camshaft hole. -- Confined largely to the immediate area surrounding the hole, as this is the only are that matters --. The surface is remarkably easy (seems to me anyway) to reduce. Within minutes, I had removed the high spots at the bolt holes. After circa 20 mins, had created a flat surface for the cam plate. I also did this to the cam plate as an experiment. The two now mate together with no visible gap between, Tomorrow, I will remove all the remnants of the gasket from the block and engine plate, and bolt in place, and repeat the polishing. Im sure some of you remember lapping motorbike cylinder heads against the cylinder to get a perfect surface between the two. Im going to try that with the cam plate and the engine plate and look at the results with my light experiment. I think it will work, but if not, Ive lost nothing. I still need another engine plate anyway. Picture later of the 2 cam plates side by side. Dinner now late.

Lawrence Slater

I should addm the engine plate still has the extra "rolling" along the areas between the bolt holes, and the actual contact area is pretty thin at these points. A decent engine plate would have more surface contact area. Again picture later.

Lawrence Slater

Lawrence, No attempt to answer your question, or directly comment, but some random thoughts which you have sparked off: I thought that way back you had said that the cam plate was not reversible? i.e. if flipped over the bolt holes and/or the oil feed hole wouldn't line up? But I also see that you have remembered flipping the cam plate over 25years ago as you surmised it was wrongly fitted. The cam plate clearly has two running faces as the side facing outwards must contact the back of the sprocket. You can see the wear ring on the outer face clearly on the Haynes photo that you posted on 20 February 2012 at 21:22:39. Maybe the triangular marks were on the outer face and are imprints of spreaders designed to stop the cam plate from arching outwards as it is tightened onto the block? A bit like the oblong spreader plates that go under each of the sump retaining screws? Having lapped both the engine plate and the cam plate, will this not now affect the end float of your camshaft, possibly taking it out of its tolerance range? If you have thinned the engine plate in this process, you may not even get within end float tolerance even if you fit a new cam plate. Clearly as it controls end float one wouldn't use a gasket behind the cam plate (although it would be one way of preventing oil from squirting through there) But maybe one could use a smear of Hylomar?

Guy

Guy, The cam end float is controlled by the width of the shoulder on the back of the cam sprocket and the cam plate thickness so grinding the cam plate will effect it but not grinding the engine front plate. Lawrence, I would assume from your description of the front plate surface that it may have been made from what is called "pickled and oiled" plate as that has a slight blasted appearance. Basically the black oxide formed during processing the steel into sheet/plate is pickled off with acid leaving a clean surface which is then oiled if required for protection before subsequent processing.

David Billington

Right, so one could use a paper gasket behind the cam plate if one was worried about oil leakage there, without it affecting the end float.

Guy

Using a gasket behind the cam plate would alter the alignment of the timing gears, but could be compensated for by adding shims to the crank nose.

Dave O'Neill2

Dozed off after eating, must be tired. I'll edit and put up the pics tomorrow, my eyes are dancing.. Meanwhile, yep the camplate is pinched between the camshaft and sproket, and then bolted to the engine plate. I have thinned the cam plate as a result of removing some of the high spots, and this will add to the endfloat. But it won't matter as there was too much anyway, I just wanted to experiment to see if I could make a better mated surface between the two. When I get a new camplate, it should cure the end float problem. Ah pickled. Me too lol. But at least that explains the finish then. As for flipping. If the dull softer face is designed to be against the camshaft as I believe, and from the Haynes the oil feed hole is roughly adjacent to the "over flow" hole, then that explains the hole spacing. But you can flip it over, which moves the oil feed hole round. I'll fit and picture tomorrow. It can only go one way which ever side you fit it, because the holes only line up one way per side, if that makes sense. Is the positioning of the oil feed hole on the clock face relevent? Why are the holes unequally spaced? If the imprint marks are spreaders, why aren't they listed as parts? Or do you mean a user improvisation? Did my memory invent them or not? In any event it can't have been the engine plate face that did the imprinting, as it's flat. I wondered about a sealent or gasket, but figured the internal environment too harsh, and it might come lose/leak -- how would you know?. Also there was nothing originally. Here is an additional thought on parts -- re camshaft plate. We used to buy factory originals. These were pretty well always near on spec. Even pattern parts had to be on spec, else no one would buy them, although there has always been rubbish around. Now with the factory parts gone, there is no one to enforce the adherence to specs and quality. What if my cam plate,and perhaps Bobs, is a poor copy? The factory item I saw today was even worn, so must be flat, even though it has some degree of indenting. (looks worse in the picture, than it did in the flesh, but it's there). Mine is obviously either unevenly thick/thin, and or distorted. Could mine be a poor quality pattern part. I doubt it though as it's so old. But I really have no way of telling if it is a factory item from 25 + years ago or a poor pattern part from the same period. btw, the factory original item was kept from a first strip I understand, specifically because it is a factory original. Sleep essential now.

Lawrence Slater

You could use Stag Wellseal there - it won't wash away, along with this. http://www.ebay.co.uk/itm/Mini-Camshaft-Cam-End-Location-Plate-Austin-Morris-BMC-BL-Rover-NOS-/220944355583?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item33714f50ff

F Pollock

Lawrence, the state of your cam plate must go a long way to explain the condition of that front cam bearing. I had thought that the cam bearing contributed to the oil flow problem but I am thinking it is the other way round! The cam shaft must take a fair bit of lateral loading, with the cam followers pressing down hard and then at the front the sideways snatching load of the chain around the sprocket. If the oil was pouring out through those gaps between the cam plate and the engine plate when it should have been largely confined within the bearing that could well lead to overheating and picking up of the cam bearing white metal. What is surprising is that this oil loss wasn't showing up more on the gauge and also wasn't depriving your rocker assembly of good lubrication.

Guy

Dear Aunty Lawrence, I am still having bad dreams about whether the cam plate will flip over or not. I thought I had flipped mine (without realising that one side is white metal) but its a long time ago now. Then on here I understood that it wouldn't flip because the three fixing holes are unevenly spaced around the edge so they wouldn't all 3 fit if it was reversed. But then again you have also said that you flipped yours because it was on backwards at first. Confused of Cumbria.

Guy

Heh heh. I'll go down to my garage now and fit with bolts in place, and take a picture. Fergus, bought one of those. Sent a message asking for confirmation that they are indeed, genuine BMC NOS. Guy, I wondered, if some debris fell down the oil feed shaft when the head was off, and was laying there ready and waiting when the engine was fired up. There is nothing at all to prevent such an occurence besides diligence. And honestly, until I understood fully how the head got it's oil feed, it had not occured to me that the front cam journal was so exposed. I thought everything came from oil galleries, where bits and pieces get trapped (hopefully). Just to confuse us all even further, in the absense of a BMC technical description of how EXACTLY the timing chain is lubed, -----------. It has been suggested that the hole in the cam plate is in fact there to lube the other side of the plate for the cam sprocket. If so, and it is not intended to lube the chain, then that supply must come from the main cap. This might make sense, as there is no seal at this point. Oil is under full pressure, and must, despite the minimal main bearing/journal clearance, be expelled in small amount to the timing cover. The oil thrower as James said is there for a reason. It distributes the oil, and the chain helps with this process. If this is the case, I think responsiblity still rests with the camplate/engine plate combination to explain the over supply. That is the one thing we know. There is too much oil in the timing cover, at the point the fault reveals itself with a thick cloud of blue smoke. Unless, --- there is excessive wear in the front main. However I discount this, as 1) I heard no rumble, 2) I had a newly ground crank and bearings. I would imagine Bob and Fergus too would know if their respective cranks were knackered. Edit, and 3) I had excessive not too little oil pressure.

Lawrence Slater

I think, as with other parts of the lubrication system oil that lubricates one item is then by design, intended to move on and oil the next item. So oil lubricates the front cam bearing and some then spills out of the end gap between the bearing journal and the cam plate. At 0.003 this is fairly close and when new would hold back the pressure on the cam bearing surface oil film and minimise wear (but not on your engine where the cam plate is worn, deformed and pissing oil out, all as you have discussed. If oil is retained on that front bearing it will last better than yours has (although, as you say it may have got some extraneous muck on there too), but will also then better pressurise the feed tube up to the rockers. Given yours was leaking to that extent I do wonder about the condition of your rocker bushes and shaft? Oil also discharges via the cam plate lube hole to oil the outer face of the cam plate where the chain sprocket runs. Oil from both those sources, adds to oil coming through the front main and possibly also splashing through the "overflow" window, all adds up to lubricate the chain and sprockets. Only on yours, largely because of the state of the cam plate, it all overdoes the oiling process a bit!

Guy

I've got 3 sets of rockers in the loft, and one on the current engine. I have no idea now, which was on the spare engine. It would have been helpful to keep track, but it didn't occur to me that it was important back then. All I can say for sure, is that I most certainly have had blocked and scored rocker shafts. Maybe/probably on this spare engine. So I reckon it's reasonable to conclude a contribution from that. I did note earlier, that I have never had excess oil under the rocker cover or oil leaking from that gasket. That always surprised me as other report it frequently. I just figured that I fitted mine properly and they don't. But maybe I don't get enough oil up there to cause the problem? I have definitely run the engine with the top off, and not had oil spilling over the block. Spitting and splashing yes, but not sitting level enough to over flow. Nor have I been able to see great amounts returning down the pushrod holes. But there shouldn't be that much should there, that it's so visibly flowing down the rod holes? When filling the engine, if you fill the cover, like watching grass grow, it seems to take an age to run down into the engine. So should I have been able to see more oil under the rocker cover?

Lawrence Slater

If I check my rocker clearances with the engine running - which I sometimes do - then oil on mine overflows at the rear of the block after about 2 minutes. Its not long! Another thought - maybe those triangular marks are from locktabs? I know they are also not specified but the fact that you have found those marks on two different cam plates suggests there was some logical reason for them.

Guy

Yup I agree Guy. But if they are locktab marks, then the plates must both have been installed reversed at some point, for the imprinting to occur. Here is the pic of mine on normal and reversed. Note the oil hole displacement. Although mine does fit reversed, it's not quite the perfect fit, as in the normal position. I have now noticed that the two holes to the left of the picture, those either end of the oil hole, are slightly elonglated, as if it has been forced. So maybe after all, it really is supposed to only fit one way. I wonder why there is not a far better description of all this in Haynes possibly, but in the Factory manual for sure. Yesterdays pictures to follow. ps. Note yesterdays results at removing the high spots. Evident in the reversed picture. The black circle on the cam thrust face is there to reveal the maximum potential contact area bewteen the cam plate face and the engine plate face. I've probably got less than half of that width in places, due to the extra rounding of the hole on the engine face plate. So I reckon I need another engine plate anyway. Another point. Whilst this does almost certainly explain my problem, Bob fitted a new cam plate. The possibility is, that the replacement engine plate he fitted is damaged/distorted/ or has a recessed/rounded camshft hole as mine does. With maybe high oil pressure as a contributory factor.

Lawrence Slater

OK, That answers my question. It was always obvious enough that the oil feed hole would move around if the plate was reversed. What I was trying to ask, but hadn't made clear, was if the bolt holes were equally spaced (at 120 degrees) I thought maybe they were not, which would mean that you would only ever get two to line up if it was flipped. I note you say there is a slight difference that can, or has been, overcome. Its all looking very clean now! ;-)

Guy

My camplate next to a factory original. Note the even wear on the factory item, suggesting that it's flat. Note the 2 triangular imprints, and the one squarish one. Did someone also fit this reversed, and use odd washers/locktabs? Again, as with mine, the other engine plate I saw was flat at the bolt holes, and couldn't have imprinted these marks. It sounds fanciful. But what if mine and this other engine were by the same builder? A recon perhaps? Fanciful I know, but almost like a signature. reverse the plate and use washers to secure it. The soft white metal would need something to spread the load from the bolts, maybe someone did exactly that on all the engines they built. Or maybe there is more than one person out there that does not know which way round the cam plate fits, and seeing the soft surface thinks it to be sprocket side. Then fits triangular washers to spread the load. Or maybe, just like easter island, stonehenge, and the great pyramids, I'm inventing history to explain the evidence.

Lawrence Slater

Lawrence, I happen to have a spare engine (doesn't everyone?) I have just stripped the front to take a look see. Only problem is its a 948cc so potentially there may be some differences, but it doesn't look like it apart from the obvious single row chain. The other thing is its a factory gold seal recon. One can never be absolutely certain but I don't think it has been taken apart since the factory rebuilt it. I will post some photos in a moment. But some comparable facts: The cam plate is clearly bi-metal, steel out, white metal inwards. It is fastened with three hex head setscrews with simple star washers beneath. No other spacers, lock tabs or anything else! The screws are NOT equidistant. centre to centre they are 2.09" either side of the oil feed hole, and 2.19 and 2.145" going clockwise around. You cannot flip the plate without some considerable adaptation; one would need to file at least 1/8" off the side of the third fixing hole to do so. There is only the slightest of wear on the outside (steel face) where the chain sprocket has run. Hardly more than just scuffing off some of the oil deposit. On the inside white metal face there is a wear ring around the centre, showing increased wear opposite each of the bolt-down corners. And - (drum roll) the corners have clear triangular imprints in the white metal. The engine plate has corresponding marks as well but there is nothing on either face that would appear to create that specific shaped impression. It seems that it is caused as I originally expected, purely by the fore and after hammering action of the camshaft. It has also raised small collars around each hole where the white metal has deformed into the countersink formed by the first thread of the bolt holes in the engine plate. They are definitely not sleeves, just deformed white metal. First photo is of locking plate undisturbed. Barely any wear on the outer face. Oil delivery hole closest to left bolt. Also note quite small splash/ overflow hole.

Guy

Next is of rear face of cam plate. Same triangular indentations and uneven wear around centre hole. Although even with a straight edge the plate isn't noticeably bowed.

Guy

And (last one!) Front face of engine plate showing triangular marks. There must be something about the shape of the cam plate that when bolted down at the three points and then hammered on one side by the camshaft in the centre, the white metal deforms to form those characteristic triangular marks with the rounded corners. I also measured the plate thickness where it has been hammered and it is thinning it by around 0.004"

Guy

When I rebuilt my engine, several years ago, I did fit a new cam plate, It was a genuine factory one as I got it from a BL dealer. The old one I recall was a little marked but not to excess. When I replaced the front engine plate the cam plate looked fine with no serious wear and the cam end float was well within tolerances. I had no reason to check the plate was flush but it all seemed to go up snugly. I renewed the front engine plate gasket and assembled with Hylomar. Because the original engine plate had fractured I also had the crank out and had it rebalanced. Journal wear was minimal (good these steel cranks!) and I just renewed the bearings. I did not check the cam bearings assuming them to be ok. It may be that the oil flow from these due to wear is higher than factory design. It occured to me that the original A series did not have the breather in the front cover so any excessive oil pumping would not matter. Its only in its latest incarnation the problem arises. BMC would not have seen this problem possibly? The 1275 engine seems to run a higher oil pressure than both its earlier ancestors. Certainly mine is comfortably over 70PSI hot at over 3000 rpm. I am running with a 13 row cooler. It seems to me that there is not one fault but a combination. None of us (Laurence and Me) have rebuilt an engine completely but have renewed obvious parts and assumed the rest is ok.

Bob Beaumont

Sorry, that didn't upload. Take 2. All I have done is to wipe of the oil deposit on the plate. Incidentally, the inside of the cover is pretty dry. Certainly no evidence of it having been regularly filled with foaming oil. Of course this engine doesn't evacuate via that chaincase but to me I doubt if there was ever much more than a heavy mist or low cloud of oil in there.

Guy

Drum roll indeed. :) Well that rules out washers or lock tab I reckon, but doesn't explain why the cam plate I saw has two triangular shapes and one squareish. I also can't see how the cam moving back and forth wold make those impressions. Wouldn't you'd hear that amount of hammering? And once compressed by 004", the camplate would no longer be clamped down tight, the bolts would be lose. Although I did say mine were not overly tight, so maybe that actually happens. Is it possible that there is some internal reinforcing on in the camplate, around the bolt holes, that could create the impressions. I note the corresponding pattern on the engine plate, buts that's an oil stain and washes off. And the wear on that camplate, is as you say uneven, not as bad as mine, but uneven nonetheless. Overtightened? I bought a 1275 Silver Gearbox once, direct from Leyland in Balham South london. Six weeks later I was sitting on a cretan building site stripping it, becuse they had used the wrong size spacers on the 1st gear selector. It moved forward enough to let sprung loaded balls pop out and prevent me from getting out of 1s gear. Point I'm making? Is it possible to fit these badl in such a way, as to cause these marks and uneven wear? But let's say that your's is perfectly normal, and the camplate/engine plate combo are innocent, even on mine. How then is oil reaching such a level in the timing cover, that suction can grab it? You spoilt my theories, I'm not playing anymore. LOL

Lawrence Slater

"I doubt if there was ever much more than a heavy mist or low cloud of oil in there." Your engine plate looks like the one i saw yesterday in respect of the "dryness" of the oil residue. Also the cam plate looks as if it has smears of dryish greasy looking oil, rather than the liquid variety I found on mine. I assume your engine has been sitting around for quite a while. Mine sat for 14 years, but the oil on the face of the timing plate, was far more fluid than yours appears to be. So if mine and bobs and fergus's are filling with oil and yours didn't, is the explanation as Fergus describes below? If so, how to combat it, what part to change? Can you magnify the rolled edges of the Camshaft hole? The plate I saw yesterday was far less pronounced than mine. From your picture yours looks the same as the one I saw yesterday, but being up close and personal is the only way to really see it.

Lawrence Slater

Can't say I've followed every nuance of this thread so apologies if this point has been raised.Clearly every time you change gear the crank will move forward against the thrust washers forcing the cam gears and chain to realign back and forth - or attempt to. This repeated movement will load the cam plate and fixing screws with a heave ho action and once worn sufficiently the free play will increase to a tapping motion, which may explain the uneven wear, pressure marks and deformation. In terms of the oil entering the chimney I still hold to my bender theory. At a certain height oil is simply picked up and thrown everywhere. The early splash ring doesn't stop oil going tsunami in the neck and if you have enough suction the oil feeds the inlet. A band aid fix would be to include an 'in line' adjustable valve to limit the flow so there's a minimum negative pressure in the crankcase but insufficient to draw the oil far enough to cause the problem.

F Pollock

Actually I didn't think any of what I posted undermined your (Lawrence) theories. Quite the opposite, I think it supports them! I also agree with Fergus' thoughts as well. I think what is happening with the triangular marks is this: The plate starts off with the three 7/16" setscrews properly tightened, with their star washers. The cam plate is firmly held against the engine plate. When running, the rapid fore and aft nudging of the camshaft begins to cause the wear ring around the central hole and at the same time is casing a levering effect by the centre of the plate being pushed outwards. This begins to cause the deformation of the white metal under the three bolts. Whilst one might expect this to be just under the circular washers, something to do with the geometry of the plate, where it is supported, where the leverage occurs and the overall shapes of the holes and outer edge combine to create that characteristic triangle - except for your one straight-edged exception(?why?). Once the white metal has begun to deform even the slightest amount (say 0.001") the bolts become relatively slightly loosened and the process continues, or accelerates. The bolts on mine were still tight - or at least needed a spanner to move them. But not very tight, just fingertip pressure on a correct sized combination spanner. I think that the only reason the wear on the back of the cam plate is in those three arcs is that as the camshaft pushes the plate outwards the segments between the bolt fixings flex outwards whilst the bits adjacent to the bolts are held rigid and wear. There is no way you would hear any hammering noise either, with it inside the engine, slavered with oil and we are talking of a bare few thousands of an inch movement at worst! The impressions left on the front of the engine plate can just be felt with a finger nail, but are really more of a print of the white metal transferred onto the steel than actual wear marks. Although mine has the marks like yours, there was no visible gap between the cam plate and the engine plate as on yours, even when shining a light through from behind. So on mine, oil discharge is still pretty well limited by the clearance between the end of the journal an the plate, even allowing for that bit of wear.

Guy

Guy you beat me to it. The washers are there, they are hidden. They are the steel side of the cam plate. Exactly as you say, the bolts clamp the steel side down, and underneath the soft white metal deforms if they are too tight, and perhaps over time anyway due to heat and continued pressure from the bolts. The base of the "triangle", is formed from the the circumfrence of the engine plate holes, as they roll away. I can't explain that Square one, but maybe there is something odd about the rear of that plate I didn't spot. Like yours my bolts were not lose, but not tight either. On the 23rd I wrote ---- "They weren't lose, but weren't very tight either. Just fingers with a 3/8th rachet undid them. Of course after 100thou+ miles, it's no wonder they might be loser than when first installed." Perhaps this then? When I first re-used that cam plate, it was already deformed at the bolt locations. I still remembewr it was on reversed, so could have been used twice before. anyway, I reveresed it, and tightened it up some more, not seeing that I was further deforminbg it and creating a gap under the cam plate, where it mates to the engine plate. Oil is forced under pressure between that gap and fills the timing cover. The rolled edges of my engine plate are eroded over time 100+ thous miles). I may well have overtightend those bolts. The steel sleeves, aren't man enough to resist the bolt clamping anction, and just sink down into the engine plate. Over time as the engine heats and cools the clamping force of the bolts on the camplate is eased, and when inspected appear to be exactly as you have described. Not lose, due to the star washers preventing them turning, but not tight due to the now thinner white metal, which has spread out. If that explains mine, how about Bob and Fergus? Fergus re used his, and "maybe" the same kind of thing applies but less so. Bob used a new cam plate. Over tightened, to cause an instant gap by deformation? How tight is too tight? what is the tolerable torque setting, not for the bolts, but for the surface of the cam plate?

Lawrence Slater

Bob and I also both swapped from the mushroom PCV to the y piece. Bob also swapped his engine plate. I don't recall the problem with the Mushroom, and that's not surprising, because it shuts on high vacuum. Which is why earlier the proposal to go back to the PVC mushroom was mooted.

Lawrence Slater

My boltholes in the cam plate don't have steel sleeves. Just the white metal that has deformed outwards to create little lips to the hole. Its very even and they do look live inserts but they are not, they are definitely just deformed white metal. Over-tightening might deform the plate to start with, but I I think unlikely and I don't think it is a necessary first step in the form or wear that then takes place. Reusing or re-tightening an already deformed plate is much more likely to cause it to bow as its is fitted. The triangular bits at the end on mine are about 0.004 thinner so subsequent re-tightening of these would lever the lengths between outwards, possibly to the extent of creating the gap behind the plate as in yours. I looked again at mine. There is no evidence of oil flow between the cam plate and the engine plate, it lies on there perfectly flat. So no oil erosion to photo either! I think if/whenever rebuilding an engine I would in future replace that cam plate as a matter of course. And I would certainly do so if it showed even slight triangular marks. Once those have formed it would be well nigh impossible to tighten the bolts without causing some deformation of the plate and likely result in gaps between it and the engine plate.

Guy

"Once those have formed it would be well nigh impossible to tighten the bolts without causing some deformation of the plate and likely result in gaps between it and the engine plate." That's it then? That's the root cause? I can buy that. The first thing noticed on mine was that obvious distortion of the cam plate. The erosion of the engine plate follows. Mine must have been bad enough to create a problem from the beginning, since I had oil suction from pretty well as soon as the engine was started. I then followed all the false trails, including bearing recessed in the block. Fergus, I tried the inline restriction approach. Mine was a a series of smaller and smaller bore pipe, inserted into the breather hose to the Y piece. It only worked when the bore was so restricted, that there was almost no suction. I conluded that wasn't the solution. Logically, the velocity of the oil through the breather hose would speed up wouldn't it? Maybe not enough to maintain volume, but I certainly got enough oil even when the internal of the hose was barely open. If it needs 1/2" internal to avoid + sump pressure, anything less can't be as good, and as the engine wears, and blowby increases, presumably more suction would be needed. I think your right a preventative measure is needed irrespective of the cause. I think sump case relief alongside the timing cover breather is the way to go. The sump breather would counteract the the potential to +ve pressure, and at the same time resist the pull from the timing cover. To do this, both would be connected to the Y piece, at a T before it.

Lawrence Slater

If you are a believer in achieving a negative pressure in the crankcase, which I am although not everyone agrees this is possible. Then adding extra vents defeats the process. Letting air into the crankcase by adding extra vents means that the extraction system just pulls air through with no resistance and it won't then produce a negative pressure. But maybe it would work with additional breather openings fitted with one way valves - just a thought! I would accept that on a worn engine this may not be possible anyway, with excessive piston blow-by. If negative pressure is not achievable, then the solution is just to allow as much open passive breathing to the outside as possible, probably not requiring any sort of suction and therefore one can get around the problem of adding octane-reducing oil vapour to the induction system

Guy

Regarding this; "The oil thrower as James said is there for a reason. It distributes the oil" It's main reason for being there is to sling the oil away from the seal to aid in it's sealing capacity. A common technique with pumps etc.

Alex G Matla

Guy, I didn't explain myself clearly. I agree I want the PCV. I think it's good and don't want to vent to the air. My modification is to add ANOTHER connection point. The regular one connects to the timing cover, just as now. The hose come up towards the Y piece, but is connected through a T piece first, which then connects to the Y piece. Meanwhile, ANOTHER hose is run from and additional breather canister connected to the drilled fuel blank. The hose from this connects the the remaining pipe on the T, and thus they are BOTH connected to the Y, and to the carbs. Suction applies to both. If +ve sump developes, it is countered by both pipes. But the draw is from both sides of the front of the engine block. Directly fromn the sump, and via the block small opening in the block. If the oil fills, and a vacuum developes in the timing cover hose, that will cause more air to enter the oil filler cap, down into the sump, and the vacuum will try to release by sucking on the breather connected to the drilled fuel blank, rather than the timing cover. But all the time the breather is still drwaing away from the potential of +ve sump pressure. Ah Alex. So you think there may be more oil in the timing cover by design then?

Lawrence Slater

Sounds good. I missed that the second breather would also be connected to the carb vacuum system. I have seen others add extra breathers and then wonder why the vacuum system no longer works and the car starts leaking oil! In fact one other aspect of your excess oil in the chaincase could be that the pressure extraction system is strong enough to create a pressure gradient between the main crankcase and the chaincase, such that oil is positively sucked through between the two, via the window and maybe even drawing oil up through the drainage holes in the front main? Too speculative perhaps, but your dual extraction would help to counter that.

Guy

Ps to my connection of another canister. The pull through the 2nd canister will be to pull against the oil column in the timing cover hose, but from the other side of it, via the small block opening that we call an "overflow". In that sense, it will turn it into exactly that. A manifold assisted overflow. LOL. we posted at the same time.

Lawrence Slater

No, but you would be amazed how effective a smooth surface spinning at high revs displaces oil along it's axis. Even air, the ventilator effect of an axle spinning at 30000 revs like a steam turbine is amazing. It would suck the oil out of it's bearings!

Alex G Matla

This is also why I don't understand how Petes works connected to the rocker cover, unless the oil filler cap is blocked completely, and the air is drawn via the timing cover. But even if it is, the draw only has the very small spaces of the cam follower tubes to operate through, and as someone said somewhere, not all of the these have drain holes in them, that might assist the process. If the oil filler cap is the plastic vented type, all you are doing is sucking air in the cap, and out of the rocker back, not the sump. I believe that on Minis where the connection is to the rocker cover, an, an air inlet is mounted on the gearbox.

Lawrence Slater

Alex, that's interesting. The thrower is fitted, concave side forward.

Lawrence Slater

Look at this picture and read what Alex posted about the effect an oil thrower can have. I haven't got a picture before I took the oil thrower off my engine. However, it is leaning against the sump, probably how I took if off. Note the F stamped on the rim. The Haynes manual says the oil thrower is mounted CONCAVE side forward, but contradicts itself in the picture, where there is also an F stamped on the oil thrower. Does this mean anything? Should the thrower be around the other way?

Lawrence Slater

Original Workshop Manual (BMC) confirms that F faces forwards, away from engine. It also says, in bold, that " the early type front cover and oil thrower must be used together". But no illustration so it isn't really helpful. Your photo isn't that clear, its difficult to see what shape that thrower face is in 3-D! It sort of looks as if it is concave, but with a central domed bit that goes over the crank sprocket central nose.

Guy

Yup, I'll look later, but I think it's essentially flat, except for the protruding bit on the nose of the crank. What did yours look like?

Lawrence Slater

Yup, if it's concave it's inperceptable, at least mine is. So F is front, and Haynes has it wrong in it's instruction, but not in it's photo. Nigel are you reading this? :)

Lawrence Slater

Its just a simple saucer shaped one. Its all back together so I cannot photo it but it is different to the ones on the later two row chain engines. But the dished side is forward

Guy

Ah so haynes confused the two. On the later ones it's flat.

Lawrence Slater

My Haynes shows one very much like the one in your photo, unless I am misinterpreting your photo. It looks like it has a raised central piece.

Guy

Yup it does, but the dish halo is flat. Maybe that is what they call concave, and just meant to say the concave side should face the rear and not forward. Interpretation. Me I would call it a flat thrower, with a protrusion rather than a concave or convex washer. Or a flat thrower with a concave/convex center. Over all though may it's concave/vex depending on which way you hold it. I'm asking on a Mini site, if anybody has torque settings for the cam plate bolts. How tight is too tight?

Lawrence Slater

If you were using a new flat cam plate, I doubt it would cause any distortion by tightening it up really well. The limit would be the torque applicable to those small bolts. But if the "ears" are already worn on the rear face, then tightening would cause the plate to distort. Which is why I now think one should fit new, if there is any indication at all of pressure marks on the ears.

Guy

Yup Guy I agree. In my case it all came down to my user error, although I won't get to test that theory until I build the engine and drive it in the next cold weather. And that's not going to be until the end of this autumn. But how about Bob? Where does this leave the owner of this thread?

Lawrence Slater

Here's the cam plate from the 'test-bed' engine. Look familiar? I think that the other camplate you saw which had 'even' wear, may just have had more wear, so it had worn all the way round, deeper in the usual places.

Dave O'Neill2

Oil throwers on 948 and possibly 1098 engines were dished. They probably changed to flat with duplex chain, I guess.

Dave O'Neill2

Dave your right about the other cam plate I saw. Because I have the original pic I can look at the file at higher res than I can post here, and what you say is true. Even in the picture I posted below, Posted 28 February 2012 at 13:08:31, you can just see it now you've mentioned it. So the moral is, never re-use a cam plate. It's not just about endfloat.

Lawrence Slater

But this now raises another question/problem conundrum, -- potentially. If you take a new cam plate, and your camshaft, and cam sprocket, and assemble them, out of the engine, you should get the correct amount of end float. The camplate must remain flat, and the thrust of the camshaft journal is evenly spaced with respect to the distance to cam plate thrust face. Then you insert the camshaft in the block and tighten the bolts to lock it in. The cam plate immediately deforms slightly, as evidenced by the wear on the picture of the cam plate that Dave has posted, and moreso on the picture of the plate that Guy posted. Thus the endfloat on an uninstalled but assembled camshaft/plate/sprocket is one measurement, but different on the installed item?

Lawrence Slater

PS. I've just been told by a chap on a Mini site, that Rover quote the torque for the bolts at 8lbft

Lawrence Slater

It's as if you need anti-crush tubes/sleeves in the cam plate, to prevent the bearing surface compressing at the bolt holes.

Lawrence Slater

I don't agree that tightening a new cam plate will deform it. I just don't think that the white metal deforms that easily when clamped against a flat face by the pressure exerted by those three bolts. What causes the deformation is the bending of the plate as the camshaft moves back and forward with axial loads caused by the skew gears to the dizzy drive and snatching from the chain with movement of the crank. These are very small movements, but in time begin to cause the triangular deformation of the "ears". Only once this deformation has been initiated would any further tightening of the fixing bolts cause the cam plate to arch outwards as yours has done. Thinking about it, I can also see why those deformation shapes are such distinctive triangles with rounded corners. It is caused by the interaction between a bending force and a clamping force, giving a sort of interference pattern that relates to the physical dimensions of the plate and the fixings. Maybe I should draw a diagram.

Guy

Yup Guy a diagram would help. I agree about the initial tightening, and that the real problem is the re-use, once the plate is compressed at the ears as you call them. Good description. Although, if the plate is over tightened from the outset, the white metal material must deform/compress. I don't have a scrificial plate to test this with, as mine is already compressed at the ears. But if the Rover quoted figure of 8lb is correct, I can easily imagine that I exceeded that. I don't know how much it would take to compress the ears, but I'm sure the bolt and block threads could take enough to do it. I said earlier that I wouldn't have gone past 10lb, but that feels like almost nothing on a med sized torque wrench, even if I used it. I probably used my 3/8" drive bar and socket. 10lbs is so easy to exceed, and without the guidance of a tech spec, I might have felt that I would rather over tigthen, than have these bolts come lose under the cover. I've checked my block face. And guess what, the threads in the block are pulled proud of the face! Anyway, now Dave entered the frey with his almost unused plate, we can see the first signs of contact occur at the ears, and as the wear in the cam plate progresses, it gradually begins to travel the whole circumfrence of the plate, as in the other plate that I put up. As Dave says, that plate has deeper wear marks at the ears, and more shallow wear at the centres between the ears. So the hammering you refer to, would first push the plate out at the ears, but in fact at that point no gap developes. Instead, when re-used, the gap between the engine plate and the cam plate, developes between the ears, as you described earlier I think, arching by the lever effect excerted in subsequent tigthening of the bolts. Did you also note my comment about the uninstalled cam plate/shaft/socket combination? If the cam plate wasn't pre-loaded by clamping it to the engine plate, you would expect the plate to wear evenly around the whole circumfrence. But in fact when installed, it doesn't. It wears in that now recognisable way. Something about all this still bothers me. I still don't think we have the answer, not all of it anyway. We only really know, that for oil to behave as it does in this fault condition, there must be too much oil in the timing cover. The rest is so much guesswork, much of it mine, and it still nags me that there is something significant missing, that is being replaced by supposition and clever invention.

Lawrence Slater

Looking at the dimensions of the cam plate it seems quite a weedy component, and the universal deformation, arching and wear characteristics makes me wonder if the thing can't be improved. So what if it was possible to make a stiffer version - one that didn't bend, wear out and cause oil to escape quite so readily. Given the critical hole centers remain what materials, shape and thickness would it need to be to make it sufficiently rigid?

F Pollock

In answer to Laurences point about my original request, it seems there is no obvious answer or a least an easy fix. Although I did use a new camplate when I rebuit the engine originally, I did not replace it when I subsequesntly renewed the front engine plate, wear was minimal and I achieved the correct amount of endfloat. The problem therefore could be: 1) Too much crankcase pressure 2) Worn camshaft bearings 3) Worn cam shaft plate (not convinced however) 4) Too high oil pressure? 5) Blocked breather cap Apart from (5) and possibly (4) it all points to an overhaul. Not something I was planning on an engine which has only done about 20K miles uses little oil, does about 30MPG and still pushes out 75BHP on Slarky's RR!!

Bob Beaumont

Fergus, how come you always get there first? lol. I was thinking along the same lines. If the plate was wider, it could perhaps be fixed at 3 additional locations, betewen the current "ears". That would prevent it arching, and allow for reduced bolt torque, since there would be 6 of them. However the engine plate on the side of the so called overflow hole is too thin. So your idea is far better. Is that the real thing? It looks as if you've just made one? What's it made from?

Lawrence Slater

No, it's just smoke and mirrors. When you consider the 'A' Series and the zillions of mods done to virtually every component, again and again it's a little surprising that neither the factory or the tuners ever sought to improve it. If there's a next step I think we need a friendly metallurgist and a source of white metal bearing steel to trial - any suggestions.

F Pollock

I have one suggestion. How about reinforcing the existing one? There's not much room, but there's enough. All that's needed is a way to prevent the centre sections arching. If a strap, perhaps a reversed bow (sprung), were to be added, in the shape of a large trangle, with the appropriate sized hole in the centre, and clamped much like a large washer, secured at the 3 bolt holes, that would a) spread the load more evenly at the ears, and b)prevent the centre stretches arching away from the surface of the engine plate. The most troublesome area, would be the side with the small oil feed hole. So the strapping washer couldn't have as much contact area at that particular point. However, 1)I don't think it would need great force to keep the cam plate from arching. 2)The strapping washer can bigger overall, than the cam plate, so if only it's inside circumfrence were in contact with the cam plate, that should be sufficient. This strapping washer can be quite thick if needed, as the only clearance issue is the nose of the camshft sprocket. As long as the camshaft sprocket runs freely inside the large hole in the strapping washer, I think this will work. I'll try and draw something if this isn't clearly explained. I need to assemble the camshaft/plate and sprocket to picture it. What do you think?

Lawrence Slater

Yes, the distance behind the cam gear needs to be measured and an allowance for the end float factored in. The reinforcer could be cast iron or sprung steel, and even use countersunk screws if it aids clearance. The stiffer and more rigid it can be the better.

F Pollock

Is this really an issue with the cam plate? I'm guessing that they all bow and wear in this way, but not everyone has the cloud of smoke issue.

Dave O'Neill2

I'm with Fergus and Dave on this as so many engines have been built in all sorts of tune and I've never heard of the cam plate being modified. The simplest way might be to make a new plate from thicker material, the steel thicker, as the stiffness goes up with the cube of the thickness. Allowance would have to be made by machining the back of the cam sprocket to suit.

David Billington

Dave, I completely agree with you, this concerns me too. We don't 100% know,if this is the real cause. However, whilst they all wear this way, it doesn't appear that they all bow. Guy checked his and there was no gap. On the other engine plate I saw, with the cam plate lying on it, there was no gap. With my engine, I have identified a gap under the cam plate. Maybe caused by my re-using an already compressed one and overtightening it, thus causing it to bow. However Bob used a new one, and still has the same problem of sucking oil. So I confess, I'm still not 100%, and don't think anyone is. But in the absense of another cause? If you have a better idea for the cause, I'm all ears. I'd love to find out that I had done something really really stupid when I built my engine. It would be far easier, and I'd willingly put my hands up to being bloody useless. But is it likely that Fergus and Bob made a stupid mistake too? I've also heard from a racing chap on a mini board who has experienced the same thing on a number of new build engines. His solution was to dump the PCV, and add more breathers, because he never found the cause. Fergus, I prefer your heavy duty version of the cam plate, but if it's cost too much to make, then at a push a stiffener could be home made. Here's my very crude drawing of one. As long as the central hole in the triangular washer is large enough, it will clear the sprocket. Are there any US, or other EU, or AUS, or anywhere guys reading this, who may have some thoughts?

Lawrence Slater

Lawrence, one way to find out; put your engine back together again, bodge a perspex timing cover and build an engine stand. Start'er up and look what happens. Easypeezy! Oh, and youtube it ofcourse!

Alex G Matla

Not the first time I've thought of exactly that Alex. In fact this afternoon, I was thinking I'd ask on here if someone has an old timing cover they don't want. I'd put in a thick perspex window and run it on my current engine in the car. Take of the fan for a better view and just use the electric fan. Only need a few moments to see how much oil gets in there. It might be interesting. Or as you say put the spare back together and put that in the car. Wouldn't take long, it's only got the front and head off. Sump and bottom is all still complete, including a sump full of oil. Somebody like to donate a sacrificial timing cover?

Lawrence Slater

Back again! Lawrence I do think you are trying to over-engineer a solution unnecessarily! By which what I mean is that if you re-assembled with a brand new plate and tightened the holding bolts correctly, you should have a system that would work perfectly well for many thousands of miles. Maybe 100K The reason that your plate was bowed outwards to allow excess oiling is that you took a used plate where the "ears" had already been deformed thinner, and then tightened it down hard. The effect of tightening the thinned ears down would be to lever the intermediate sections outwards allowing the oil to leak through. The solution is very simple. Redo it properly, as designed, and it will last as long as most other components on the engine. Its not as if it is an expensive part! That's 275 posts on this topic, and many of them are long ones too! Is this a record? I know that Welsh sheep was longer, but they were generally much shorter messages!

Guy

Guy, I'd completely agree with you except for one thing. Bob used a new cam plate. If we are reasonably sure why mine has the problem, and it was all down to crappy skills and laziness, that still doesn't explain at all why Bob has the problem. And as I posted earlier, it doesn't explain why a chap on a Mini forum, had the problem on several new builds. That leaves room for some doubt in my mind. Also, trust me on this. If this had ever happened to you, and you had stripped and rebuilt the engine several times, and never found a solution, then while the engine is out, and already in pieces, you'd be looking not only for a fix, but for a prevention as well. You're right. I could put it back together. Then I have to wait for at least 8 months before the weather turns cold enough to even test if it has worked. Suppose then that it hasn't? I'd then have to drop the sump. Drill a hole in the fuel blank for the additional breather, and then strip off the timing gear, and start looking all over again. It would be winter, and I don't fancy doing it in the winter, garage or not. Over engineer or not, I'd rather be certain than disappointed. A little more effort now might save a lot more later. And if it wasn't needed, what have I lost? Do Welsh sheep drive Spridgets? Or any sheep for that matter? lol.

Lawrence Slater

Do you not remember the Welsh sheep thread?! Its not that Welsh sheep have an interest in spridgets, but that certain spridget drivers take an interest in Welsh sheep. Allegedly! Maybe that's the difference. I am a lazy optimist. If I don't have to do something I won't, and I justify it by believing I will never have to! What is needed is for Bob to strip his engine and examine his (newish) cam plate. Maybe his blue smoke problem is resulting from a different source of oil to chaincase flooding anyway.

Guy

Well can't find sheep in the archives in the numbers you mention, but I can well imagine the "connections" some people may have been making to sheep. :) I hear they are a strange lot,,, sheep I mean. You never know who'll they'll bond with. As for this being much effort, it's not really. All I have to do is make a large trangular washer to cover the cam plate. The only other extra is, drill and then re-blank the fuel blank on the block, in preparation for it potentially being needed later. Everything else is the same. I have to strip the engine anyway, and rebuild it anyway. So putting a plate over the cam plate is no extra affort at all. Thinking about Bobs engine. The first thing to do without stripping anything on the front, is investigate the oil pressure. Confirm the gauge is accurate, and then investage the oil bypass for a blockage. I figure mine must be and I'll take a look tomorrow. If you can reduce, don't do anything more until next winter until it's cold enough to show the fault again. I reckon you can rule out the oil filler cap. If it was blocked, it would act against the vacuum pulling on the oil in the timing cover, although, arguably it would allow pressure to rise in the sump that would act in favour of the oil in timing cover. But, as you've already tried the paper trick, and it sucks and doesn't blow, I reckon the filler cap is excluded. That leaves doing a partial strip, but only of the timing cover and gears, to take a look at the cam plate/engine plate in situ. If you can get a feeler gauge under the long sides of the cam plate, then at the least you might need a cam plate. If there is still a gap with a new cam plate, you need an engine plate, and if that doesn't fix it, your no worse off, and you can try the extra breather system to see if that works. And then dynamite!

Lawrence Slater

I suppose the cam plate should only get distorted if the crank end float exceeds the end float of the cam. In this situation whenever the clutch is depressed the crank will move forward - exceeding the end float limit of the cam and the skinny thrust plate deflects to take the rest, bending it and then setting up the witness marks. When correctly assembled the cam end float should be .004 to .007" and the crank .002 to .003". So in theory the thrust plate should enjoy small clearance assuming the gears are running perfectly in line.

F Pollock

Fergus, I would have thought that lateral slack in the chain links would work as a damper to the transfer of loading from crank to cam. When I say as a damper, I mean that forwards movement of the crank would be transmitted via the chain to the camshaft, but without any direct force. Sufficient to accentuate the wear ring but unlikely itself to bend the cam plate. I still think that action on the helical gear drive to the dizzy will have an axial component on the camshaft, which may be the cause. Another possibility, that I see you also imply, is that if insufficient care is taken to align the two sprockets on initial assembly, then there could be a forwards loading on the cam plate continuously, not just because of crank movement.

Guy

One thing I've never checked when installing the distributor drive gear is the amount of pre load - if any exists, once you've bolted in the housing. If there was any preload here the helical drive would transmit these additional loads forward to the thrust plate. I suppose an easy check would be to reinstall the long bolt and see if the drive gear has any end float on its seat.

F Pollock

Well, I definitely didn't check for pre loading on the distribuor drive gear. It wouldn't have occured to me, and what could you do about it anyway? New disributor drive I suppose. As regards the crank endfloat, and cam/crank sprocket alignment, I can exclude those as causes. It was a newly ground crank, and the the right over size thrusts were installed. I also distinctly remember making sure of gear alignment with a straight edge, and although my cam plate was (it's very apparent now), knackered, the cam endfloat was ok. Having said that though I do reckon that all these things could be important, if the setup is perhaps always so close to the point that too much oil enters the timing cover. It may well be that there are many engines close to the edge, but far enough away to avoid it. I also think that there are many engines out there with this problem, that because they are used in the warm weather, the ownwer will never know.

Lawrence Slater

Dizzy drive end float apart, that helical gear will still provide some axial force to the camshaft at every change of speed, although it shouldn't be much when it is only the lightweight dizzy! Here's another observation for you Lawrence. You say that the camplate on your engine was initially fitted the wrong way round. The fixing bolt holes are definitely not equidistant so in order to fit it the wrong way round it must have been modified - holes filed oval? and possibly forced to get all three bolts in. Maybe this distorted the plate right from the start? I know that you then flipped it the right way around, but if it was already buckled by a few thou that could have started the whole excessive oil leak saga.

Guy

Yup, I agree with you guy. The holes on my camplate are offset(elongated) just enough to allow the bolts to go in. It's not much, and it's not a perfect fit, but once the bolts are in, it "fits" and appears to be ok. It didn't occur to me back then. So you may well be right about that. Also, for me to imagine triangular washers, I must have seen the charactersitic wear marks at the ears, and that implies that the cam plate had been on the right way to begin with at some stage. That's very possible because I got the engine from a breakers yard, sometime in the early '80s, and by then, if say it's a late '60s engine, it had probably been re-built more times than hadrian wall. But it had good end float so I used it, not even thinking about any other aspect. Interestingly, I just had a telephone chat with a bloke who suggested the following. He wonders if the camshaft might not have been fully seated, when the cam plate was bolted down. If it wasn't, the effect would be to bend the cam plate. The cam wouldn't turn too well of course, so I guess you'd unbolt and free it, then the camshaft goes in properly, and the problem disappears, but you don't notice you've already bent the cam plate. The other thing he wondered, was if the plate was completely flat to begin with, maybe, had been bent at some other point prior to installation. Even at the factory. It wouldn't take a lot, and who checks them for flatness anyway? Dave Oneil recently said that he once assembled a camshft and end plate, and the shaft wouldn't turn, because the plate was too thick. Maybe the quality of even genuine plates has varied a little over the years, not enough to matter 99.9999% of the time, but on rare occasions enough to present a problem.

Lawrence Slater

PS, someone on a mini site posted that both sides of the cam plate are bearings surfaces, "The cam retainer is a thrust bearing on both sides, the hole lubricates the chain pulley to retainer face." It's quite possible that on my engine, someone thought that most thrust was from the sprocket, and not the cam shaft, and made the plate fit that way. I think most people would know which way round it goes, but as the holes are "almost" right for it to be flipped, maybe someone figured the holes were just slightly out of line, and "fixed" them so they could put on what they thought was the right way.

Lawrence Slater

I am loathe to stick my completely ignorant nose into what I think is one of the best threads I've ever read on this forum, particularly as I've never even stripped an engine down or to be honest known anything about cam plates other than their vague existence. However from what I have learned from reading this thread, noting that we now believe the forward motion of the cam is causing a gradual slight distortion in the cam plate and thus letting oil seep through in sufficient quantity to accumulate in the timing cover and eventually be gulped into the carbs, is there any possibility that some after market hotter cams (and I seem to recall Lawrence, Bob et al developed the symptons after fitting these)are not made to the exact tolerances and are causing a greater/faster distortion effect on the cam plate than might be expected over many miles of normal factory cam wear? Many apologies if everything I have just said is just ignorant guff, its just that having read the whole thread you've got me thinking about nothing else now too! Keep it up!

Matt1275Bucks

Ah sorry Lawrence. Just seen your post of 11.26 and subsequent. This thread is moving too fast to keep up!

Matt1275Bucks

:) Welcome to the discussion Matt. I rather suspected that not only was this thread boring the pants off everybody else, but was probably annoying them off too. So it's good to hear you find it interesting. :) Hotter cam was a consideration by me from the outset. It's the first thing I swapped out to try and fix it. I thought the extra induction caused an increase in vacuum and caused the problem, and it may well have contributed to it, when the excess oil was already in the system. But it's not the prime cause. I now have a slightly damaged 270 sitting around because I wrongly blamed it 25+ years ago.

Lawrence Slater

I doubt that a hotter cam as such would make a difference. But Matt does raise the possibility that an aftermarket cam (of whatever temperature) could be dimensioned out of spec in such a way that it didn't push fully home and thus cause the cam plate to bend when tightened. The only problem I see with this is that the camshaft should be floating, positioned fore-and-aft only by that plate. Unless the oil pump was fitted wrongly or not engaged properly? After fitting one would at that stage turn the cam to see that all was well, and check that there was a minimum of 0.003 thou end float. but if it wasn't, then the plate could be already damaged. I am speculating here on a re-assembly prior to Lawrence's engine build. We know that by the time Lawrence rebuilt this engine the cam plate was already well past its best! Lawrence, when I checked the bolt hole alignment to see if the cam plate could be flipped mine would have needed one of the holes to be elongated by a good 1/8" - probably half the hole diameter. You wouldn't even get the bolt started without some drilling or filing. But a sufficiently ham fisted PO might have got bored with filing when it was nearly there and used something like a small podger (see windscreen fitting thread) inserted into the hole to heave the thing into alignment. Since we are only talking in terms of thousandths of an inch distortion causing the initial excessive oil flow leak it really wouldn't take much! Just in from the garage doing some welding. Set fire to the Sprite in the process. Quite exciting! Its surprising how big the flames can get before they are visible through a welding helmet! LOL!

Guy

Well I'm glad you saved the Sprite first. btw, was everyone else ok too? LOL Gotta have priorities. Yes, I forgotr to comment on that Guy, my holes are only maybe a 16th" longer most. It's haredly noticable. They are a little oversized, but again not by that much. That's why by just flipping and looking, it looks like it would go right on with no trouble at all, and it only takes a little jiggle to get the bolts in. More and more it looks I have a very dodgy cam plate.

Lawrence Slater

No problem with the Sprite. Its the MK1, not my current road car Sprite. And no damage, just sundry bits of cardboard, sponges rubber matting a plastic bucket (that burns well!_) and the old wiring n the back of the dash, which wasn't fitted at the time. 1/8" is what would need to be filed off one hole, if the other two were persuaded to align. If two holes were filed, then I guess elongation of 1/16" on each would do it.

Guy

All aftermarket cams - other than those specifically cut fron a billet are reground old ones. I once had a Piper Magnum 285 delaminate in a big way showing the rusty cam it was based on underneath. When I rang Piper I was told that unless I had used their followers and valve springs they wouldn't be held accountable. But yes this raises the question that if cams like these have been metal sprayed and not recut properly, something could be well out of tolerance. But of course when we pull a new cam out of the box we assume it's dimensionally spot on and just install it.

F Pollock

Hmmmm. I need a new cam too. I've been looking at the prices, and as soon as I saw the price was exchange, I realised they were built up and reground. Solid metal cams seem to be twice the price. Where do the likes of Moss and Sussex get there's done? Whilst on the subject of cams, I've noticed something interesting. I pulled the piper 270 early on becuase I thought it might be the cause of the problem. when I got it down from the loft recently, I had a quick look and decided it was hardly worn, but a little surface rust had damaged the journals. However today, I had a closer look, and the marks on my front cam bearing are just visible on the 270 cam. So the bearing damage must have happened very early on. So I compared it to the standard cam that was in the engine for the bulk of it's 100+ thou miles, and it's the same, just worse on the standard cam. Then I noticed something. The scoring/scuffing, and the mark that corresponds the deep score on the front cam bearing, is only on ONE side of the cam journals. The same on both camshafts. This leads me to think I had a timing chain problem from the outset. You know how bike chains can stretch more in one section than another, well, I think my timing chain must be like that, and has been excerting more pull on one side of the cam than the other. Either that, or the sprocket(s) were off concentric. Anyway, I think the bearing is worn more on one half than the other, sort of ovalled. This could shift some more of the blame for extra oil supply back to the front cam bearing. Pic later if I can capture it.

Lawrence Slater

Logically, there is much more sideways load on one side of the the cam. All of the pressure of the rockers (i.e. the valve springs) exerts only downwards. And the snatching of the chain as the crank accelerates and decelerates is also predominantly downwards and down left. One would expect the front cam bearing to wear far more on the bottom and maybe the 6 to 8 o'clock section rather than any others. I know you posted a photo, but I couldn't work out what orientation it was at. Does this theory match the wear section on yours?

Guy

Yup that's exactly as the picture posted 23 February 2012 at 11:02:04 shows it. The top of that combined picture shows the front bearing up the right way, with the oil feed from the crank, coming in from the left at about 9o/c, -- the slotted hole. If you look at the bottom of the bearing there is definitely more wear. But why is the cam journal only worn one sided? In places the lobes are alsmost 180 degress opposed. 1 and 8 for example.

Lawrence Slater

Just to discount the camshaft idea, I am using a standard original cam, not reground or modified in any way. As regards the oil problem, it is less prevelent when its summer etc but can be a problem on summer mornings when its chilly and the car has been outside all night. I cannot believe out of all the hundreds of A series engines around only 3 of us have experienced the problem!! Is it an issue with transverse engines? ( my 1300GT and MG 1300, the latter which was well worn, never had such a problem). It does not affect the smaller capacity engines nor single carb set ups. Only it seems those 1275 units with the Y piece going to twin SU's. I would stress my engine is not worn and when I did rebuild it I used all new bits all ex factory.

Bob Beaumont

Bob, this must be one of the longest ever technical threads, but way back near the start I posted an "oil fart" theory which I believe mine was doing(its why I added that oil catch tank shown on Peter's thread. Why did you discount that idea for your engine?

Guy

Bob, I totally agree with you. I don't think I posted this yet, but I'll make it short anyway. Are you familiar with Andorra? I've been through there in the Sprite maybe a dozen times. Not for while though. Drive up from France, go through to la vella, and on down to Barcelona. When you leave Andorra la lella, there is a long decline down into spain. The engine cools nicely, and mine would cool enough to suck oil. I was camping there for a week once (Andorra), and drove up, going North, back towards France just to enjoy the view from the top. I blasted the car all the way up. When it got there it was pretty warm, but the air was cold. We spent a couple of hours up there, and then drove back down. On the way down, I don't need to tell you what happened. It can't be a fart Guy, if bob is getting what I get. But what Bob says does trouble me. New parts, probably built better than mine, and still the same problem. PS. Yep a guy on a Mini forum told me he's had it too.

Lawrence Slater

I agree that the symptoms described seem the same, but I don't think it is properly established that the cause is the same. Mine was doing what I would describe as blowing a cloud of blue smoke from the exhaust some minutes after starting up, which then subsides again. Mine was then continuing with a bit of a blue haze. I added my coffee tin oil catch tank and it has more or less resolved the problem. Although I am convinced of the process that resulted in blue smoke clouds on your engine, Lawrence, I don't think that necessarily means that the same process is involved in Bob's engine. It would need some investigation to confirm exactly what is happening.

Guy

<< It does not affect the smaller capacity engines nor single carb set ups>> Smaller capacity engines do not have the breather on the timing cover.

Dave O'Neill2

That would explain it then Dave. Guy, I don't know what's happening in Bobs engine, but his descriptions of the oil cloud, and when it happens, are identical to mine. So the timing cover must be filling with oil. The question is, why. We think we can explain mine by what we know about my worn cam bearing, excess oil pressure, overly rounded hole in engine plate, leaky engine plate gasket, and of course the poor state of my cam plate. It all makes reasonably good sense. But most of that doesn't apply to Bobs engine. Only the excess oil pressure, and maybe the changed engine plate. So I agree, there could be another cause, in Bobs engine, and that could also mean, that we haven't really gotten to the bottom of why my engine does it. What we need is a live test. But it's not easily done, or maybe even at all. My clear plastic pipe proved to me that the cover was filling with oil, but really I knew that anyway, and that only confirmed it. The only other thing I can think of, as Alex also said, is to put a window in the timing cover and try and watch it. But I doubt you'd see much for all the oil splashing around, and you can't see behind the sprockets anyway. Guy, if yours was the same, the coffe jar would fill with oil.

Lawrence Slater

Here's a Morris Minor engine. Note the breather on the rocker cover which vents into the air filter. Also, the second breather on the tappet chest cover, which vents to atmosphere.

Dave O'Neill2

Guy, I have changed the hoses in response to your 'fart' idea which I was attracted to if only in name!!, see my earlier post. The original hose was worn but not blocked. The new plumbing seems to be fine but I have not had an opportunity to try it out fully. It does not do it whilst warming up in the garage but then it didn't before. My engine as I said before is a very early 1275 (thin wall block)and would have had the PCV valve originally. The later 1275's used a subtly different casting (thick wall block). I don't know but wonder if there is something in the design of the engine blocks and oil ways whichj was changed when the Y piece breather system was introduced. We are all pretty much agreed the timing cover must be filling with oil to an excessive amount albeit momentarily at critical engine oil temperature. There has to be something we are missing still.........!

Bob Beaumont

Cam bearings: Yes, Lawrence, those are the bearing photos I was referring to. Just needed confirmation as to which way up they were as my spare engine is back together again now. Bearing asymmetrical wear is explained by lateral loading of tappets and cam chain. The only explanation I can think of for the wear on just one side of the cam journal would be a slight eccentricity (bend? - or machined) in the camshaft? I still think that you are making an unproven step in your supposition that the cause of Bob's symptom is exactly the same as yours. It may be, but for me it isn't yet proven. To me its at the stage of, if you have a broken arm and I have a broken arm, that doesn't mean we both fell down the same flight of steps. You may have got as far as saying both broken arms were caused by impact damage, but not much beyond that! I never thought my engine was gulping oil. It produced a considerable cloud of smoke, but it does that when I restart after doing a wet compression test when I add a measured 3cc of oil from syringe -that's about 1/2 a teaspoonful. If gulping oil pulled in enough to fill my coffee can oil separator, I think it would do more than blow a cloud of blue smoke! That is enough to cause an immediate hydraulic lock! I think that these blue smoke problems may have different causes. I am sure you are right about yours - although I doubt it is pulling in quite the quantity that you seem to think. It takes only a small quantity of oil to create a lot of the blue stuff! But I also think that mine is the result of oil condensation inside the hose which then gets drawn through by the vacuum when the engine next warms up. Maybe not as dramatic as yours though, but that fits my symptoms and my investigations.

Guy

Goodmorning Bob, Sorry, I was busy typing when you were posting! Although I described solidified oil in the hose liquefying and being farted through, on consideration it requires so little oil to produce a significant blue cloud that I think the same may apply with relatively clean hoses. The conditions needed would be warm oil vapour being pulled through the pipe when you switch off;a cool night for this to condense on the inner walls of the pipe; and maybe a pipe that was routed so that there was a good length than sloped down towards the Y piece rather than draining back to the canister. Then some while after starting this cold engine in the morning that oil condensed on the walls of the pipe heats up, vaporises and is pulled through to the carbs. In terms of the quantity of blue smoke I am pretty sure that this is sufficient to produce the symptoms that I have had. (mine no longer does it since I added the coffee can which is low down, well below the carb.) If yours is gulping oil through from the chaincase, I don't think it is necessary to explain this as pulling in a continuous column of oil. Lawrence's may do so but if momentarily the canister inlet is engulfed in oil that would still do it. It would gulp a blob of oil, produce blue smoke, falter the engine revs, drop the amount of induction suction, stop gulping oil, and then recover itself, leaving a blue screen in the road behind to drift off in the morning sunshine.

Guy

Ah, there's the nub of it. Still nobody really believes me, or Bob I guess. I guess I understand why too. It took me quite a while to believe it myself. That's why I fitted the clear plastic breather hose, and why I still have it on my current engine. Guy. The hose from the timing cover to the Y piece is over 15 inches long. At 1/2 inch bore that is sufficient volume to hold just less than 1/3 of a pint. That's just the pipe. The breather canister holds some more. Try pouring that lot into the engine and watch the results. And once it starts, whilst the engine is still coldish, it continues. Or at least it would until the timing cover level went down, or more usually I stopped the engine to stop it happening. I didn't allow it to continue indefinitely, to see when it would stop on it's own. I'll say it again. There is no doubt at all, that a continuous column of liquid engine oil, over 1/3 PINT, was being injected into my manifold. That amount of oil can only come from one source. A partially full timing cover. Not condensate. Not a burp a hiccup, or a fart or a plug of semi solid oil/sludge, and not droplets. A continuous column of oil. And I'll say again the tail pipe of the exhaust pipe, was wet with oil, and the plugs were soaked after the event. A dense cloud of smoke, not a vapour trail. Bob is describing the same thing. He is agreeing with my description. Hence he must have pretty much the same quantity of oil being sucked up. I'm not saying it's the same cause, because frankly, we don't really know the cause in my engine either. All we do know, is that the timing cover must be full to at least the level sufficient to cover the entry hole to the breather canister. That is all we know. I think, you'll never believe it, unless you see it for yourself.

Lawrence Slater

I've called the pipe 15" becuase that's the appx distance to the Y piece before I swapped to the HIF44. So you can also add in the pipes from the Y piece. An unbroken flow of engine oil. As impossible to believe as that is, it was happening. No mistake about it. None whatsoever.

Lawrence Slater

Don't fret Lawrence. I did say that I believed your diagnosis for your engine. That was clear. I also said that mine at one time was also producing a sizeable cloud of blue smoke, but that I thought (am convinced even) that in my case the cause was different. The amount of blue smoke I was getting was comparable to when I do a wet compression test with 4 X 3cc oil. I put that in to give some sort of quantification of what will produce a lot of smoke and also because I thought others would be familiar with wet testing and the smoke screen that results when restarting. From your estimates, yours is gulping in perhaps 25 to 30 times as much! That, is a LOT of smoke!

Guy

lol. No fret guy, no worries. Exactly Guy a lot of smoke, exactly as I know it to be. The explanation for yours is highly plausible, and as I said right at the beginning, I'm sure there could be an element of it on mine too, maybe Bobs as well. But this is a different dimension. There is another reason I posted those last pictures. I've mentioned several times, but haven't really pushed the point, that my current engine suffered the sucking oil syndrome, when first re-built, and until I put on the HIF44. I said that the new cords rings, might have contributed to this as perhaps they took time to seal the bores. So the score is, 2 of mine, 1 of bobs, and 1 for fergus, and at least one for a chap on the mini forum. That's 5 engines, all 1275, and 1 transverse. My current engine is more akin to Bobs, in that it didn't have me re-using a flipped over cam plate. Of course it did have me re-building it, and if it still sucks oil, the common denominator may well be me, something I am doing very wrong. I would dearly love that to be the case, and actually suspect maybe it is. I just can't think what. It occurs to me that maybe I should try putting the twin hs2s back on my current engine, and see if I can induce the problem again. If it does, that gives another line of enquirey. I'll have to get the twins down and take a look at them tomorrow. See they are still alive.

Lawrence Slater

Looks like I have to take off the hiff anyway. There's a mark on my rocker cover that could be a blowing exhaust manifold gasket.

Lawrence Slater

I've just found 5 other people, Spridget owners, who had the same problem. Same cold weather symptoms, same warm up period, same embarrassing cloud of smoke that can't be explained as condensation. And no solution was ever found. They are in the 2009 Archives in one thread. I'll get the name of it and post a link later. Eat now.

Lawrence Slater

Just to be clear (sic) my cloud is quite dense and will last for about 1/2 mile when travelling at 25-30mph. Its not just a puff of blue smoke. It only does it just the once however despite however many times the engine is stopped and restarted that day.

Bob Beaumont

1/2 mile at 25 - 30 mph is only just over a minute. Still, probably more than mine when it was doing it. Mine was an embarrassingly large cloud of blue smoke, but still more of a short belch, which more or less stopped after a few seconds, just leaving the blue cloud do drift over the adjacent pedestrians.

Guy

Guy, I've just read the 2009 thread properly, and you were posting there too. Nobody realised what it was. 2009 technical archive. Thread. "1972 1275 midget producing smoke" http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=97&subjectar=97&thread=200903100740502958 Do these sound familiar? "Ian, this is exactly the same problem I ave with my Midget, start it up all looks fine get 1-2 miles down the road and then time for the james bond special smoke screen. I to thought and was told when I purchased the car that it was valve stem seals, when I took the old head off I found a broken valve spring so I purchased a head off e-bay and fitted that with new valve stem seals on both inlet and exhaust (wait for the opinions on fitting them to the exhaust!!!) All looked promising all fitted drive down the road the first time and no problems, I now realise I stood it on the driveway warming up first to make sure I had no leaks before the test drive as I had no screen, next time though queue smoke screen." And. "I have exactly this problem with a 1973 1275cc Midget. It has done 6000 miles on a recon engine and the problem has started to occur in the last 1500 miles or so. The smoking occurs after driving for about 1 mile and is accompanied by a rattling/pinking - sounds like the oil pushing past the pistons? After about five minutes the problem disappears. The car runs at 80 psi dropping to about 70 when hot." And "Ian I had exactly the same problem which was the oil seperator/breather on the front crank case of the engine. I ended up cleaning it out and disconnecting the closed circuit pipe and fitting a small K&N breather to it. It was always a bit of a mystery but it cured it! Jody" And "Does it only happen in cold weather by any chance?" They were contributors either with the problem, or had heard of it. Are they still on the BBS? I Milton, Tyne and Wear, United Kingdom J Shaw, Essex, United Kingdom Shaun, 72 RWA, 67 Sprite, Norfolk, United Kingdom Jordan Gibson, Healey Frogeye, Northumberland, United Kingdom I D Wadddell, Staffordshire, United Kingdom Notice the comment about HIGH OIL PRESSURE. Crankcase breather my thread from 1998. http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=20037171504047&mode=archiveth&subject=early/78&subjectar=110&thread=E199810281548300

Lawrence Slater

well at least you are consistent! I still always have trouble with the archive. It just does not want to work for me. Even those two links don't find anything that I recognise as the thread you are discussing!

Guy

Guy, try this. http://tinyurl.com/8357hpy You may have misunderstood. They were not my posts, those were other people. ALSO, I have now found 14 more threads that nobody understood. The usual diagnossis was bad rings and valve stem seals. The usual solution when that didn't fix it, was disconnect the breather and install a filter or catch tank. Plenty of posters gave BIG clues about the timing cover filling up. I believe this is a very common but unrecognised problem, both sides of the Atlantic. The state of my cam plate and engine plate, must exacerbate the problem, but they are not the sole cause! Even on my engine. I still don't know what is. On many of the posts I found (all technical from 1998 to 2005, then I got bored), there is a mention of high oil pressure. Could this after all be the most significant factor?

Lawrence Slater

A combination of high oil pressure and worn cam bearings, possibly.

Dave O'Neill2

Thanks Lawrence, That last Tiny URL worked OK. The earlier two archive links you did both just opened up a new current 2012 messages page, my normal Last Posts view. Not6 sure why. Anyway, yes there have been loads of discussions about smoking engines, which display a range of symptoms, some very similar to yours. Yours always was a smoker but you are not the only one. But similar symptoms are also caused by other things too. On that particular thread I was talking about over-supply of oil via worn rockers. An almost parallel situation involving starting from cold, thick engine oil being pumped at pressure through worn bearings and limited oil drainage out of the closed space via restricted drainage openings - all of which equally describes your chaincase or my rocker cover. So I quite agree that the scenario is right. Where it does seem to differ is that in the rocker cover the consequence of oversupply of oil is simply that the guides are immersed and then oil is pulled down the stems into the manifold chambers. Whilst in your case the suction actually initiates a semi-continuous process of sucking up oil.

Guy

I am not right in thinking that 'James Bond' actually removed his breathers and used a K&N filter but still had the problem?

Dave O'Neill2

No, I think he cured it by periodically turning the car upside down to clear the excess oil from the breather cannister. He devised a quick method using an airborne spiral roll technique to avoid scratching the paintwork.

Guy

Dave, what he posted was "I even tried removing breathers etc but that did not cure it, I suggest checking your oil levels as mine needs topping up frequently" That was Shaun, 72 RWA, 67 Sprite, Norfolk. He doesn't say that he didn't put the breathers back on. He gave up and went for a K series. Jody "cured" it by disconnecting it. "I had exactly the same problem which was the oil seperator/breather on the front crank case of the engine. I ended up cleaning it out and disconnecting the closed circuit pipe and fitting a small K&N breather to it. It was always a bit of a mystery but it cured it!" Guy, YOU were talking about the rocker cover being the cause of the problem. THEY weren't. It's very obviously not "similar" to mine, but EXACTLY like mine. Guy and all. I just posted that I have found 14 other threads from the years 1998 to 2005. I could have gone on right up to date, but I didn't bother. There is no need. Different people from different years ALL describing exactly the same thing. This is not oil in the rocker cover. This is oil from the timing cover. I honestly don't understand why there is any reluctance at all, to accept that for some reason still unexplained, oil is filling the timing covers on significant number of 1275 engines, and being sucked into the induction. LARGE amounts of oil. FORGET my TWO engines. There are at least 15 other people who have reported exactly the same problem (even though many have not understood it), including Bob who started this thread, who does understand it. Bob knows the oil is coming up the engine breather, hence the title of the thread. Yes of course, cracked rings, bad valve stems, poor drainage from the rocker cover, and a number of other things, including small amounts of oil droplets and mist, CAN cause an engine to smoke. It's VERY common. So what? This is different! So please, suspend your doubt, take it at face value for what it is. Forget about condensation, leaky valve stem seals and anything else, and let's concentrate on THIS problem and it's cause. I've always believed that others must have this problem. I posted it here in 1998. Until Bob started this thread, I thought I was the only one who had posted about it. Now though I see there are over a 15 other posters all describing the same thing. This thread has consumed a lot of peoples time, including mine, and I've enjoyed it. It has also forced me to gain a far greater understanding of the working of the system that provides PCV and lubrication to the timing chain, and made me realise how few people understand it. So I understand now why nobody has EVER come up with the PRIME cause of the oil sucking issue. I will continue to post here if only to amuse myself, --- if nobody objects. I hope that others will also keep posting.

Lawrence Slater

The chain needs oil. The timing cover has 2 sources of engine oil. 1). The open crankshaft front main bearing. 2), The almost closed off, camshaft front bearing. Assuming no wear, those are fixed openings through which oil can be supplied. If the openings are made larger, more oil can be supplied. Just like a tap. We THINK we understand exactly how the oil is delivered via the cam plate to the timing cover. Let's assume we're right. Oil from the camshaft is delivered via an open ended groove in the front camshaft journal I have just noticed a DIFFERENCE between the grooves in the 2 camsshafts I have. The grooves are bigger on one than on the other. This would be like opening a tap further. However there is another variable. Oil pressure. Increase oil pressure and you increase supply. If you don't increase drainage, and if the pressure is increased, and or the tap is opened more, the cover will fill with more oil. Yup Dave, I agree, it's beginning to point back to the bearing again, but I think more likely it is beginning to point to oil pressure. I also think that for any one engine, it is going to include aspects of other variables such as sump pressure, thickness and grade of oil even, state of engine wear and components, degree of inlet manifold vacuum, state of tune etc etc. But irrespective of all of those possible contributing and aggravating factors, there must be a single overriding cause of too much oil in the timing cover. Find that, and all the other factors, on their own, won't cause the problem. That's what I think, and that's what I'm looking for.

Lawrence Slater

About oil pressure; I have an adjustable oil pressure relief valve. Because too much oil pressure is a waist of horse power, and it heats the oil unnessecairy. I still do think the only way is to run the engine outside of the car with a way to see the oil level in the timing cover, be it a window or a simple clear tube fixed at the bottom and top, a looking glass so to speak.

Alex G Matla

Lawrence, I have said almost as often as you have argued the point, I believe you. I accept your diagnosis. I wasn't trying to say that it isn't caused the way you describe it. What I was saying however is that not EVERY case of sudden blue smoke is down to that one cause. Mine certainly wasn't. Presumably the ones that continued to do it even when the breather was disconnected weren't either. I was commenting however that the circumstance of cold oil being pumped into the chaincase and not draining away fast enough, is mimicked by oil accumulating in the rocker cover on mine. Both situations occurring when the oil is slow to drain away and both seem to relate to an oversupply of oil because of worn bearing surfaces. Incidentally, I recall that some years ago there was a discussion on the Spridgets@autox forum about the circumstance of oil being sucked up the breather pipe as you describe. Probably around 2003 I would guess.

Guy

Is this the longest thread ever?

Jeremy 3

No, but we're working on it ;o)

Dave O'Neill2

Alex, what do you mean clear tube at the top and bottom? I already connected a clear plastic hose to the breather, that was how I confirmed the cover was filling with oil? Anyway, I know how to investigate this a little more. All I need is a "CHEAP" timing cover, with or without a breather canister, and it doesn't matter if it's damaged, because I'm going to cut a hole(s) in it. 4 methods. 1) Put the cam in, to seal the bearing hole. Plug the oil feed to the head. Put the cut out cover on, pour fridge chilled engine oil in, and time how long it takes to drain the cover. 2) Put the cam back in, but leave the chain off and spin the cam with a drill ( through a hole). Watch as the pressure builds, and squirts oil into the already cut open cover. Watch as the oil drains. 3) The head's off so there's no compression to overcome. Put the chain back on and spin the crank with it. Watch effect of chain on oil. Messy option, unless I make a perspex window, However my oil is black and I don't want to change it on this spare engine as it would still be murky. So this will be an open observation. 4)Cam in, chain on, cover off, spin engine with drill. Try to observe oil from front main and cam bearing, with and without cam retainer plate. (No distributor drive, so no forward cam thrust). I'm going to fiddle with option 4 tomorrow, as I haven't got a sacrificial cover yet, and because it will be interesting. Actually though, I think it's a bit of waste of time. We know the cover is filling with oil, if it wasn't this thread wouldn't exist. But I'd still like to see close up, how the oil enters the cover.

Lawrence Slater

Another thought just struck me. Perhaps the oil sucking is also self aiding. Once the cover fills to the required level, and the vacuum takes it, a siphon effect will also be pulling on the oil. Even if the suction from the manifold reduces, for a while (small) at least, the oil could still flow. I could refit my good cover, and try this with a tube as soon as the canister if full.

Lawrence Slater

I ment like a sight glass, a level indicator. And the only way to reduce manifold suction is WOT right? Not a thing you do when lots of smoke erupt from your car. So if you close the throttle in reaction to the smoke, you actually make it worse, until the cover is emptied out

Alex G Matla

That's the thing Alex, it's not that straight forward. It's closing the throttle that really initialises it, and makes it worse, until the revs drop. But once you open the throttle, the vacuum drops off a little and allows the oil to settle back. So in theory the oil flow should ease off. That's how I used to counter it sometimes, if I didn't stop the car. I used to dip the clutch, and let the revs die, then gingerly build up the revs again, and often, once the current batch of oil had gone, that would be it. But it didn't always work, and I was wondering if that might be due to some siphon effect. So I tried it today, with a can of oil. It's pretty easy to pull a vacuum, and get oil to siphon from one can to another. So I think that once it starts, until the column of oil breaks, it's also aided by siphon. That's where Guys valve would do the trick. Air would enter the system, and break both the vacuum and the siphon. But my preference is. 1) Identify the prime cause, and 2), add the 2nd crankcase breather on the fuel blank. I looked at my oil pressure bypass today, and the plunger was sticking in the block. The trouble is of course, my engine has been sitting for 14 years, and that may be the cause. However, once out there was no surface rust, but it is a bit scored. Now I've read that the common problem, is that it sticks open and reduces pressure. But as I always had high pressure, I don't think I've ever paid it much attention. If it wasn't lifting of it's seat enough this may be the cause of my high pressure, and maybe a big factor in the excess oil flow in the timing cover. I think once I strip the engine completely, I have to make sure all the oil galleries are blasted clean somehow.

Lawrence Slater

<<I have to make sure all the oil galleries are blasted clean somehow. >> The normal method is to drill out the gallery plugs and use bottle brushes to clean out all of the crud. You could talk to your local engine 'shop about chemical cleaning. What oil pressure do you have on your current engine when cold? What did you have on the old engine?

Dave O'Neill2

Hi Dave, Yeah I'll ask about chemical cleaning. I may have imagined this, but think I read somewhere that on an old block, this is not such a good idea. I can't remember where or why though. Any thoughts? As regards pressure. I'll start it soon whilst it's still cold and check, but it's 80+ always, even in mild weather. This was always true of the spare engine too. As I say, I used to believe this was a good thing, so didn't connect it in anyway with something I should cure. In fact the opposite is true. I think the higher I could get it, the happier I was. However, irrespective of it being involved in this problem, I now realise, that apart from it being a power drain (which I suspect is minimal and not a worry on a road car), it's not actually good for the engine or the oil in other ways. Excess heat and wear being two factors directly related to excesively high oil pressure. That said, if this were to come down simply to too much oil pressure, I'd be pretty surprised though, as well as kicking myself for a self induced problem that has plagued me for 25+ years. lol BTW, I know my oil pressure gauge is accurate, as I have an almost new spare (broken temperature sender bulb), that I checked the one in the car against. They both read the same.

Lawrence Slater

Another angle on the high oil pressure topic is that what it really means is too much restriction on oil flow in some part of the system. This then means less volume of oil pumped around the system in a given time so it can mean less cooling of the high pressure spots like bearing surfaces.

Guy

I didn't catch it in time to show it at almost 100psi, but you get the idea. Even when at around normal operating temp, I can pull at least 70psi when the revs are up to around 35/4000rpm. It would easily be 80 psi at say 3500 after a couple or minutes/miles. So why no oil sucking on the this engine? I swapped from twin hs2s to a single hif44, and before doing that, this engine did suck oil. But I had also just re-ringed with cords, and there could have been excess crankcase pressure until the cords sealed the bores. So this is not at all clear cut. Is it certain that the take off point for the oil pressure gauge is an accurate measure of engine oil pressure? Or could it be a measure of the pump pressure, before the pressure bypass reduces it? I'm guessing the former, but confirmation welome.

Lawrence Slater

I’ve not read all the posts on here so I’ve missed it – in simple short terms on these type of Spridget A-series engines what is >>the working of the system that provides PCV and lubrication to the timing chain<< and off topic but on your Prop mini-dash you’ve got a vacuum gauge, I always remember a RR tuner telling me that if you wanted fuel economy that was what you needed, I can’t think that why you have the gauge so I’m curious to know what do you use the gauge for also: >>I honestly don't understand why there is any reluctance at all, to accept . . .<< yes I know how you feel - it’s a matter of belief(s) and you yourself are normally a prime example, you can have a strong belief to your version of the logic to a matter which means you do not accept another belief and version of logic to the matter dare I suggest using a thinner oil to drop your pressure or would that put more oil up your pipe

Nigel Atkins

Nigel, " what is >>the working of the system that provides PCV and lubrication to the timing chain<<" They are seperate functions, that are both performed in the Timing cover. 1) The timing cover chamber is connected to the crankcase via block a small opening. So using the manifold to pull air down through the oil filler cap, through that block opening, and up out of the timing cover, reduces or iliminates crankcase pressure. So called PCV. 2) The timing chain and gears need oil. So they are fed via the front cam bearing, and probably to a lesser extent via the front main main bearing, all of which are inside the timing cover. It is the unintended interaction of these otherwise two completely seperate functions, that causes the problem of oil being sucked up the breather Pipe. If PCV isn't performed via the timing cover breather pipe, -- it wasn't on earlier engines-- then this problem wouldn't exist, and the possibility of the timing cover over filling with engine oil, likely never noticed. Actually some people have reported this fault directly after changing engine oil. I.e new thicker oil caused the problem for them. As to the other questions, I'll do another general thread as I'd rather keep this on the topic. :)

Lawrence Slater

So going back to the oil pressure. Does anybody know if a blocked oil filter head could raise oil pressure? I have the old paper type. Long ago in the mists of time, the oil filter warning light came on. I changed the filter, which looked good to me, and the light stayed on, even with the engine not running but with of course the ignition on. I put that down to a dodgy switch and disconnected it. Now I'm wondering how that part of the filter head functions, and if the failed switch is in anyway connected to high oil pressure. Could it have been damaged by high oil pressure?

Lawrence Slater

The switch may have been OK. If the relief valve was stuck open you'd get a low reading, and conversely if it was stuck shut you'd get a high one. Your start up reading of 80+lbs is too high if it's a standard spring, and hasn't been packed out to increase the poundage, as the manual gives a blow off value of only 50lbs. When I prep a block I lap the relief valve in. Apart from seeing it has a good contact area, it makes you flush everything through so it's all squeaky clean.

F Pollock

I don't remember using a longer spring, and certainly haven't added and packing. I'll measure the spring length on both engines tomorrow .

Lawrence Slater

Lawrence You have mail

Dave O'Neill2

My oil pressure reading is about that when cold. Just short of 80PSI. it drops back to 70PSI when hot at 3000rpm. I did not renew the spring or valve but it all seemed ok and moved freely. It runs with an oil cooler and spin on filter but they should not affect the pressure. Could this be the problem with excess oil in the timing cover??

Bob Beaumont

Bob, the oil cooler will keep the pressure higher, as the oil won't thin as much. But as to this being the cause, the evidence is still circumstantial, but fairly good. I'm going to try and find out why my current engine has such high pressure at start up. If I can make the bypass do it's job, maybe you could do the same and see if it cures the problem. What we need is a blast of frost so you can test it. :P

Lawrence Slater

I can only think that high pressure must be related to a) too powerful a pump (unlikely); b) too viscous oil - when cold, but design with relief valve should take care of that. c) Pressure relief valve not relieving at the corrct pressure - modified spring or jammed shut maybe? d) restricted oil gallery somewhere. limiting the ease of oil circulation. Just for the moment thinking about that last one - if there were a restriction (partial blockage?) in the gallery between the front cam bearing and the head, then it would give both a higher pressure reading and also an excessive flow out of that cam bearing. The problem with this is of course the unlikely circumstance of Bob's engine (and others) having the same problem!

Guy

Guy, we wondered about the blockage in the cam to head feed, but my spare engine was clear. Do you know the route that oil takes from the bypass back to the sump? I guess if that's blocked (partiallly) that could do it. PS, other posts I found did mention high oil pressure. Edit, the more I think about this the more I seem to think that the oil pressure on my current engine is actually increasing when it's cold. How high can a pump go?

Lawrence Slater

It does seem possible. High oil pressure, so long as it is not related to viscous oil, could well result in too much oil getting pushed out past the cam bearing and into the chaincase. Vizard has a diagrammatic representation of the oil system (page 400) Just says oil pressure relief bypass "falls via a drilling direct to the sump"

Guy

now I know this video is for a B-series engine but the board schematic and talk of blocked line, and machine shop work might jog other thoughts it's only 10 minutes so worth watching all the way thorough if only so that you can say I wasted your time again the principals, even though it's a different engine with different inards and outards just might trigger something for you by seeing another aspect or view, even if not totally related http://www.youtube.com/watch?v=a7mVVvWnR34&list=UU40j4KqUJPMVv4FQ29ro-xQ&index=155&feature=plcp

Nigel Atkins

As far as I remember, it should be reasonably obvious where the oil from the O/P relief valve goes when you have the bare block in front of you. I've had a few fairly standard, not too worn midget engines which never gave much more than 70 psi cold, even with oil coolers.

Dave O'Neill2

Hi Dave, I haven't got the sump(s) off as yet, but I'll be doing that shortly on the spare engine after I get a sacrificial timing cover and do a few tests. Very good Nigel. Best thing you've posted. Note from that Vid. It's possible for oil to get behind the relief plunger and cause a hydraulic lock, preventing the plunger lifting. There's a drain that should prevent this, but it could be be blocked. Also, although he didn't specifically talk about how the timing chain was lubricated, it was implicit. In particular, he mentioned the MGB system of lubing the chain tensioner, via a cross drilling in the block. OF NOTE, was that he refers to "oil that gets trapped behind the camshaft plate", thus confirming the A series method, that the plate acts to contain the oil behind the plate, only allowing the escape via the small hole. I'll have to look at a B plate and see if it works the same way. However, I think all this is beginning to add up. Excess oil pressure, perhaps combined with excess end float, perhaps combined with greater than designed inlet suction. The exact factors probably vary on different cars, but the overall flavour is the same, and I think that the system is always pretty close to the edge.

Lawrence Slater

"Excess oil pressure, perhaps combined with excess end float, perhaps combined with greater than designed inlet suction. The exact factors probably vary on different cars, but the overall flavour is the same, and I think that the system is always pretty close to the edge." This finally seems to make sense, and plausible without being too far fetched. I think the bend in your cam plate is probably rather more of a one-off that adds up to tipping the system even more over the edge in your case! When I say one-off, I don't mean it doesn't happen in other cases. But I think that is caused by re-using a cam plate on which the "ears" are already significantly worn or compressed. When re-fitted and tightened up, the thinner ears will bend back against the front engine plate, causing the segments between to arch forwards, away from the engine plate and providing the additional escape route for oil under pressure. Another interesting point is that I think that putting a slight arch into the cam plate in this way, will actually reduce the apparent end float of the camshaft. There isn't much in the manuals about installing that cam plate other than to "check the end float with a feeler gauge". If the plate is warped one could get a false reading, making it appear to be OK to proceed, despite the wear on the ears. The best advice would be to replace the cam retaining plate whenever fitting a new cam shaft.

Guy

>>Very good Nigel. Best thing you've posted.<< you cheeky git :) anyway I post lots of links to John twist videos >>Note from that Vid. It's possible for oil to get behind the relief plunger and cause a hydraulic lock, preventing the plunger lifting. There's a drain that should prevent this, but it could be blocked.<< that was one of the points I thought useful >>Also, although he didn't specifically talk about how the timing chain was lubricated<< he did mention it in the video >>OF NOTE, was that he refers to "oil that gets trapped behind the camshaft plate"<< another point I thought might help glad you looked at it and it was of a little bit of help I thought you might dismiss it as it was about the B-series that’s me finished with being able to contribute to this thread other than to say change to Mobil 1, 0w-40 Extended Life oil, just think how long you could leave oil changes then :)

Nigel Atkins

No that's great stuff Nigel. The B is not much more than a large scale A. Many similarities. Does John Twist have an email address/website contact form? Is he still alive and practicing his arts? It occurs to me that he may have come across this himself. I've already read a post stateside of someone with these symptoms. Guy I agree. This must be getting close to getting at the cause(s). Measured my spring in the spare engine today. Book says 72.63, mine is 71 dead. So the length isn't the cause, but the plunger does look like it has been catching the sides of the bore. Very good seat marks though. I need to get the sump off to look at the rest but before I do that, I want to do a cover fill test, and to that end I need a cheap cover. --- Working on that.

Lawrence Slater

Dave, sent you an email.

Lawrence Slater

Lawrence, you could try, I don't think he keeps very up to date with the many emails he must get University Motors videos - http://www.youtube.com/user/Universitymotorsltd#g/u web site - http://universitymotorsltd.com/

Nigel Atkins

I may be muddling him with someone else, but I believe he decided to pack in the business 2 or 3 years ago. Had a garage sale and closed it all down. But then about 9 months later he had second thoughts and resurrected the whole thing again. I think that was John Twist / University Motors

Guy

that's the guy but his wife's illness and death might have also been involved

Nigel Atkins

Yes, that was the reason but I thought that was personal detail, and it was not necessary to elaborate.

Guy

His latest video is dated 2nd March so he's clearly still firing on all 4.

F Pollock

I think John Twist said about his wife in one of his videos so I don't think I'm being insensitive to repeat it I think it might show him in better light than what you put - >>Had a garage sale and closed it all down. But then about 9 months later he had second thoughts and resurrected the whole thing again<< I can look thorough the videos to find where he gave these personal details to the world if you want and if I'm wrong I will sincerely apologise and would if I could also then delete that post of mine

Nigel Atkins

By way of an update,the engine performed ok again today. No smoke.It is of course no guarantee its cured but this is the third run out since renewing the oil filler cap and oil breather pipe to the carbs.

Bob Beaumont

Bob, if you had the same symptom I had, and others have described, and I think yuu did, then sorry to say it's not cured. It's just warm weather giving you the illusion of a cure. A new oil filler cap, would if anything make it worse, as a completely blocked one would have had the effect of holding back the oil being sucked up the breather. And as you say the old hose wasn't blocked, I can't see any way how that would make any difference. So if yours is cured, then it was the condensation Guy talked of.

Lawrence Slater

Laurence,I am under no illusion! However,the engine was started from cold (hadn't been run for a couple of weeks)and the weather conditions were similar when I experienced smoke before.But, I have now changed the oil from Halfords classic 20/50 to Castrol 20/50 which may have had an effect given oil pressure may be an issue. The guage was showing just over 75PSI cold. I have not looked at the relief valve.

Bob Beaumont

Hi Bob, Is there much difference between halfords and castrol in terms of thickness for the same weight of oil? If oil pressure is a big factor, then the oil could well have an effect. Some of the other posts I read, people reported the problem was worse after changing the oil. Well let's hope yours is sorted, but I remain sceptical. If you had the same problem as me, then not getting it now could be entirely down to the rise in ambient temperature. I appreciate the engine was cold, but not as cold as it was when you first posted this. I don't know how much thicker engine oil gets per degree f drop in outside temp, and how much that causes the problem, but it must be warmer now than then. Doing what you've done didn't solve mine, but then I now know I had a very poor cam plate at the very least, and didn't suspect that at all. Fingers crossed then, and wait for snow at easter. lol

Lawrence Slater

there should be no noticeable difference between Castrol 20w/50 and Halfords 20w/50 at the 20 and 50 bits at least I've used both in no particular order in my present Midget over the last 5 years one make may break down more than the other and or quicker than the other but I wouldn't know as I do a thorough oil (and filter) change every 6 months I did notice this winter that starting was sluggish so at last I've come to my senses and I'm going back to Mobil 1, 0w/40 like I used in my previous classics for many tens of 000s of miles all year round Lawrence, the fully sythetic oil will last longer and wear better so extended oil change intervals I might consider 12-15,000 and 1-2 years, you might go for 20,000 miles but it's more to do with the start up type and frequency and journey types all tied in with weather type - but don't ask me about it look it up on t'web oh, and the meaning of synthetic oil has stretched a bit over the years - but you'll never get over 300 posts about it :)

Nigel Atkins

Nigel you might like to read this. The Synthetic Oil Myth Then there is the myth that new engine break-in will not occur with synthetic oils. This one was apparently started by an aircraft engine manufacturer who put out a bulletin that said so. The fact is that Mobil 1 synthetic oil has been the factory-fill for many thousands of engines. Clearly, they have broken in quite well, and that should put this one to rest. http://www.nonlintec.com/sprite/oil_myths.pdf

Lawrence Slater

Whether synthetic or mineral, I always think that there is benefit in an oil change in flushing out any debris that has accumulated. With regard to this, frequent changing seems to me to be more beneficial than long change intervals. Certainly in the earlier years of synthetics, one of the "selling points" was that you could go long intervals between changes, thereby offsetting their higher initial cost. Fine perhaps on a modern engine with fine tolerances and cleaner burn engines but I have my doubts that one should rely so much on this in a 60 year old designed engine. Prices for mineral (up) and synthetics (down) have converged over the years so for similar running costs one can change synthetics at more frequent intervals which must be beneficial. Currently I am still on mineral 20W50 and I change it at 3,000 mile intervals. But I may change to synthetic, possibly running to as much as 5,000, but no more than that.

Guy

Lawrence, I was refereing to the old engines that we have in our cars rather than modern engines I will have a good read of that link though - as you know I'm not one with a closed mind a rebuilt engine will want short change flushing type oil changes so why waste your money on more expensive oil my wife had a LHD smart from new that came out of the box with Mobil 1 in it it was supposed to have Mobil 1 at oil changes but who knows with dodgy Mercedes dealers - the worst thing about the smart was its Daimler Chysler owners set up just down the road in Milton Keynes IIRC(?) at 120,000 miles a smart engine was taken apart and the wear tolerances were within what were allowed for a new BMW engine Guy, I think the thoroughness of the oil change can be as important as the frequency and the time or mileage interval can vary depending on the vehicles use, the weather and other variables I am also going on my own personal experience of using Mobil 1 for many tens of 000s of miles in classic cars including a Spridget I used to change at 12,000 miles or 12 months which ever was the sooner - I didn't have the engines stripped down and measured for wear but they all seemed to go well, I think I had over 90,000 on my previous Spridget when I parted company with it, I can't remember how many I put on but I do remember I was heading towards 15,000 miles if I'd kept it for the full last 12 months

Nigel Atkins

Since there is so much information contained in this thread, I've decided to reactivate it rather than create a new thread, or continue the discussion in the "good news bad news" thread started by Tim. Last year I stripped my spare engine to investigate the possible cause(s) of why engine oil is sucked up the timing cover breather and into the manifold. My own conclusions, based on what I found regarding the condition of my camshaft endplate, and the engine front plate, convinced me that the 'major' reason for the oil sucking syndrome is too much oil in the timing cover. I still think that along with too much suction the main cause is too much oil inside the timing cover. So to investigate that, I bought a spare timing cover from Dave O'Neill. I'm going to cut a clear window in that cover to try and see what happens to the oil level when the engine fills. I bolted back on the oil filter housing, and an oil pressure gauge. I plugged the feed from the top of the block to the missing cylinder head, head and I checked the length of the pressure relief valve spring. The spring length is 72mm, and it's the one that came with the engine 35 years back. So I assume it's the original. I removed the flywheel to make it easier to spin the engine by hand/drill. I refitted the front engine plate(old gasket with some sealant)and refitted camshaft endplate. (Last year, if you read lower down the thread, 25 February 2012 at 17:45:01 UK time you'll see that my camshaft endplate was "distorted", and the surface of the engine plate was "eroded". So I flattened both off, so that they mated properly, and eliminated the gap you can see in that picture). To begin with yesterday , I put the camshaft back in again without the chain on the crank, and used a drill on the end of the cam nut to make oil pressure. Notice the small leak around the plug on top of the block. That simulates feeding the rockers, lol. I made well over 75lbs within seconds, but by the time I took the pic, it had dropped to 50. Subsequently, just turning the cam with my fingers is enough to build oil pressure. It's amazing how you can feel the cam rotation opposed by the oil pump, as the pressure begins to build. I can feel with my fingers exactly how the oil pump robs power from the engine. Watch this exciting vid and see the oil come out. Lol. http://s1208.photobucket.com/user/slaterlp/library/Timing%20cover%20oil%20feed After this, I used a crank handle from my socket set to spin the camshaft by hand.

Lawrence Slater

Using the crank handle it takes very little speed to build well over 50 lbs pressure. You can see the oil coming from the "oil feed hole" in the camshaft endplate, and the oil seeping from the front main bearing on the crank. But notice how more is coming from the camshaft, when compared to the crankshaft. I don't think the crankshaft oil is the main feed to lubricate the chain. I think it's just the consequence of being and open bearing, allowing the oil to cover the whole of the shell/journal. I think the main feed to lube the chain is the camshaft feed. But if the front main was worn then it must add quite a lot to the oil filling the cover. Also I wasn't spinning the crank at this stage, so it'll be interesting to see how that alters the oil coming from the main bearing. But anyway, just spinning the camshaft on it's own, and at very low revs per min, it doesn't take long – less than 15 seconds – to deposit quite a bit of oil into the oil tank below.

Lawrence Slater

More to follow these last 3 posts on this reactivated thread. Notice in the previous picture that the oil is predominantly from the feed hole in the cam endplate, and none from the sides of it. There was almost none from the centre of the cam endplate either. What there was of it, was smeared round by me letting the socket contact the endplate. Then I deliberately distorted the cam endplate to give a 4 thou gap between it and the engine plate on one side. This simulates how oil escapes under the plate, when it should only be escaping from the feed hole. The camshaft endplates distorts as soon as you over tighten them. Is this the cause of the over filling versus insufficient drainage?

Lawrence Slater

You may have to cut and past the video link I gave in the first reactivated post 3 posts back from this one. Or try this. http://tinyurl.com/ldvvl8b

Lawrence Slater

Is there any scope to increase drainage by enlargening the vent hole to any degree, or even putting a rad on the edge to encourage flow?

F Pollock

I've been wondering that Fergus. But would it weaken the block? Also, does this hole appear on earlier blocks, without the front cover breather? If it does, then it can't have been a vent hole in the first place, since there would be nowhere for crankcases pressure to escape to as the earlier engines didn't have a breather in the cover. So if that's the case, it's either a casting hole as some have called it, or splash oil feed hole, or it's an overflow. I reckon I can rule out it being a splash feed hole. I span the crank today using a drill on the crank bolt, without the timing chain in place Although my drill only spins at max 2700rpm, as I didn't have the cover in place, I would have expected to get some oil splashed over me. But there wasn't a single drop of oil splashed out of that hole. I then put the chain and sprockets back on and span the engine. Unfortunately I couldn't do it for long, for fear of burning out the drill. When the oil pressure comes up, well over 75lbs, coupled with the drag of the friction of the rings in the bores, my drill began to over heat, so I had to stop, long before I'd got that much oil in the bath I was catching the oil in. So I'm not going to be able to fill the cover, with or without a viewing window, unless the engine is running under it's own steam. But I'm pretty sure the key is excess oil being fed from the cam plate. whether that's also coupled with too much suction and too little drainage, is a bit of a guess, but it probably is, so increasing the drainage in some way would seem to be a good idea.

Lawrence Slater

Even though this thread doesn't seem to be of use any more, due to it's length and lack of interest, I'm going to repeat the post I made on the other thread ("good news bad news"), as it continues the recent posts I made below. Then I can keep a copy of THIS thread on my computer for reference. Then I'll abandon this thread to it's fate. :). If I assume(for now at least) that I'm unique in fitting a badly knackered camshaft endplate on my spare engine, and have a worse case of oil sucking than anyone else, then "if" that's the case, the distorted camshaft endplate is a red herring. But I have a 2nd engine that has oil sucking, and the question remains, why do some other engines in which perfectly good new camshaft endplates have been fitted, also suffer from oil sucking? Firstly, I found the answer to my question in the other thread about the "vent/overflow/casting" hole, in a picture Guy posted back down in that thread of a 948cc engine. That engine has the same hole in the same location as the later engines. Therefore, it can't be a crankcase vent hole, as there was no breather in the timing chain cover of the early engines. If it was just a casting hole, why not cover it with the engine plate? Why make a bigger hole around it in the front engine plate? So it's clearly there for a purpose. I'm 100% certain it's not a splash feed to lubricate the chain. In my experiment spinning the engine, -- there wasn't a single drop of oil expelled from that hole into the timing chain cover. Instead, oil is delivered into the cover under pressure from two sources. From the end of the crankshaft front main bearing, and from the end of the camshaft. It initially collects at the bottom of the cover, and provides plenty of oil for the lower section of chain and sprocket to run in a bath of oil, and carry oil up with it as the crank rotates. So all that's left for the hole in the block face is as an overflow hole. But why would you need an overflow hole? Especially if there's no breather for the oil to flow out of, if the cover fills up. The two small drain holes in the front main cap, could be overcome by the oil feeding in from the front camshaft and main bearings. This might well happen when the oil is still "cold" and hence thicker, and won't then flow so easily back through those two small drain holes. Also, apart from the constant flow of oil from those two oil feeds, there's also crankcase pressure, blowing the oil back into the cover, or at least resisting the oil being drained through those two small holes in the main cap. If there wasn't an additional drain hole higher up, the cover could completely fill up with oil. With a constant oil feed, and crankcase pressure being applied in the timing chain cover, oil would very likely be forced out of the front crankshaft oil seal. So there's an overflow hole to take the extra oil back into the sump. The overflow hole in the block was introduced before the breather in the timing chain cover was introduced. It must have been expected that the oil could reach that level, but the overflow hole would prevent it rising above that. I doubt it was expected that the oil would rise above that overflow level, but in some circumstance it must be above that level for oil sucking to happen. When the timing chain cover breather was introduced, the entry hole to the breather canister on the inside the timing chain cover, was set at almost the same level as the overflow hole in the block. In fact the bottom of the entry hole to the breather canister, sits BELOW the bottom of the overflow hole in the block face. So BEFORE the oil starts to flow through the overflow, it is already flowing into the breather canister. So now with sufficient crankcase pressure, and some suction from the breather, with an already high level of oil in the timing cover, the lower oil drain holes and overflow are completely overcome, the timing chain cover fills to the top of the breather inlet hole, and up goes the oil into the manifold or carbs. But not all engines have the oil sucking problem. So what common variable(s) applies to those engines that do? All the engines, new or old, have crankcase pressure, but that varies due to wear in the engine and or modifications. Assume the oil feeds from the front main and camshaft bearings --- ignoring oil pressure for now ---, and the drain hole sizes of the main cap and overflow are considered fixed, but the crankcase pressure and strength of breather suction can vary. So maybe those latter two factors alone can combine to cause the oil in the timing chain cover to rise sufficiently above the overflow level to commence oil sucking. Higher than "normal" crankcase pressure will pose even more resistance to the flow of oil back into the sump via the drain and overflow holes. At the same time, breather vacuum applied to the timing chain cover canister, from the inlet manifold or carburettor connections, will also pull on the oil, and slow down the flow rate through the lower drain holes and the overflow hole, causing the oil level to rise high enough. So I reckon those must be the cause(s). In all engines the oil can reach quite high levels in the timing chain cover. The overflow and drain holes cope well enough with normal crankcase pressure and when there isn't too much suction from the breather. But in engines with either too much suction or crankcase pressure, alone or combined, when the oil is thick enough(usually cold), this causes the timing cover to fill with oil to a level that completely covers the breather entry hole. Then the oil is grabbed by the suction and pulled into the engine. When the oil warms up, it gets just thin enough to drain fast enough. But if there's too much suction or pressure the problem continues. Here's a picture I took yesterday, combined with a sketch of measurements, I posted in the long other thread last year. It's a view looking forwards from behind the engine front plate, into the timing cover behind it. It shows the relative heights of the overflow and breather canister entry holes. My biro cap indicates the centre of the overflow hole in the block face.

Lawrence Slater

In case my experience on this matter might be relevant/of interest, I was suffering this EXACT same issue. Car would just be starting to warm up, about a mile after leaving home, and suddenly a MAJOR cloud of blue smoke from the back of the car. Very worrying and equally embarrassing. It stopped happening when I allowed my oil level to run a little lower in the sump. I suspect my dipstick might need re-calibrating/marking but in the meantime, the blue smoke has just stopped happening! Glynn

G Williams

FWIW my thoughts - 1. The hole in the front of the block is to allow air/fumes to reach the vent in the front cover. 2. When running the engine is filled with a heavy oil mist. 3. The purpose of the mesh in the oil separator is to catch and return to the sump the majority of the oil droplets in the mist. 4. When this mesh gets dirty the gaps in it get smaller and the gas flow is higher so oil CAN travel up into the pipe to the carbs/PCV valve. 5. You get the slug of oil after a while of engine running and before the oil has thinned enough not to climb the mesh. 6. Taking out the mesh does not solve the problem because the oil droplets just collect in the suction pipe. 7. The solution is to replace the mesh with similar density clean mesh or to construct a bigger oil separator. 8. All the ideas of oil levels and pressures are totally irrelevant!

Chris at Octarine Services

Well that makes sense. I didn't clean the mesh when I rebuilt the engine originally, However I have been using the car more in the last 2/3 years and on longer runs. This has meant more oil changes which had possibly meant clearance of the gunge in the timing cover mesh. The replacement of the pipe to the cover pretty much eradicated the problem.

Bob Beaumont

Glynn: that was my experience. Low oil level no problem; top it up - trouble! I checked my dipstick thinking along the same lines as you (same names think alike!) but it was spot on. Chris: I had enough oil coming over to run the car as a diesel. Ignition off, it just kept on running. The pcv was full of liquid oil, It finally stopped when it spat back and threw liquid oil out of the small breather hole in the top of the pcv covering the underside of the bonnet (which was open, and both front wings in oil. My engine was Searle-rebuilt about 3000 miles back so I guess the mesh should (should!) be clean.

G Williams (Graeme)

Chris, appreciate your knowledge and understanding BUT how do you explain my recent experience whereby dropping my sump oil level has completely ERADICATED the problem of the blue cloud of oil smoke approx 1 mile after leaving home? Glynn

G Williams

Suddenly this thread kicks back to life, here we go again, and I can't be bothered anymore to refute the "slug of oil" formed by "oil mist" theory to account for all oil sucking. Whilst it seems it may be the cause for some, Bob's for example, it certainly isn't the cause for mine or others. Read the WHOLE thread properly and you'll see it's NOT only a slug of oil that some experience. ---- "All the ideas of oil levels and pressures are totally irrelevant!" ---- Except if you actually experience this yourself, and cleaning and or replacing the wire mesh doesn't solve it. Graeme, I've noted each time you've mentioned oil sump levels, and now Glynn has come on board and experienced the same thing. Yo'uve been jogging my memory to way back in the 80's when this first happened to me. It may be a false memory, but I'm pretty sure I remember losing so much oil to sucking that my sump level dropped and the sucking stopped when it was low. But I always topped up again and put up with the sucking whilst the engine warmed up. But how can the sump level affect this? If you look way back down the thread to my post on the 22 February 2012 at 18:11:57, you'll see a picture of the sump showing the max oil level in the sump. It's under 3" from the bottom of the sump. That's a very long way below the entry hole to the breather canister. How can the oil be sucked up from there? Graeme, and Tim on the other thread, had a problem with the PCV. Tim didn't use one, and graeme's was faulty. So the breather cover was exposed to full manifold depression. Is this really enough to lifta column oil all the way up from the sump? I know the moon can distort the shape of the earth and lift the oceans, but can the inlet manifold suction of a Spridget, really lift oil all that way? It doesn't sound possible, and I suspect it isn't. But clearly it must have something to do with this, as otherwise why would it stop if you let the sump oil level fall below maximum?

Lawrence Slater

Lawrence, I have read the whole thread and have experienced it myself on my own 1275 and my MGB as well as customers cars. I investigated and solved the problem years ago - if you really want to see what happens then do what I did - cut off the oil separator from the cover and connect the front cover to a clear tube about the size of the separator ( I used a bit of plastic pipe used as filler tube for boat water tanks) and stick one of those plastic scotch pads in it. The cold oil mist does climb the mesh. When it warms up it stops climbing the mesh. Increase the vacuum and it climbs the mesh even when hot.

Chris at Octarine Services

Chris, I've not heard of it happening to B's. How much oil, are you talking about when you say a slug of oil formed from mist? In excess of a "1/3rd of a pint" of oil? That is a breather pipe full of liquid oil, plus the breather canister. How do you explain that inspite of my cleaning my wire mesh with petrol several times it never solved the problem? I don't dispute the droplets of oil, slugs of oil, and mists of oil getting into the engine, and no doubt my engine suffers(ered) from that too, but what happens to my engines is in a different order.

Lawrence Slater

Lawrence, sorry I don't have time to read the whole thread, but I can say that my experience reflects what Chris has found. Both B's and Midgets. In practice, if the canister is chemically cleaned (as in a reconditioners tank - petrol can't do it properly) it can make a dramatic difference to the amount of oil that is carried into the manifold and hence oil consumption. "can the inlet manifold suction of a Spridget, really lift oil all that way?" This isn't a simple case of vacuum pulling it up, there is a constant movement of gases through the breather system driven by crank case pressure from combustion gasses leaking past the rings (there's a bit even in a new engine). The oil mist (yes it exists) gets carried along with it and if the separator isn't doing its job it will make it all the way to the manifold. Aerodynamic drag on fine droplets is much more significant a force than gravity. (just as anything small and light such as leaves, or droplets in a mist, get easily blown around in a breeze) Have a look at the article linked to from the thread on PCV/engine breather system by Growler recently which describes the whoile thing well. Typically the gauze in the separator becomes much reduced in efficiency after it has been dealing with a very tired engine for quite some time as it gets very gunged up doing so, but then gets no attention when the engine is overhauled. In addition, if the engine is of the type with a PCV valve and the valve is malfuntioning (as they do), that will cause considerably more flow through the breather system than intended. The result is clouds of smoke and on occasion a waste of money reconditioning a perfectly good engine which didn't need it. Yes, it has happened. I have had customers come in to me who had just that done (elsewhere I might add) only to have the engine as smokey as before, when all that was needed was a new PCV and/or a cleaned out separator.

Paul Walbran

This post: http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=thread&subject=97&thread=2013081723174512868 ...has a link to the great article Paul refers to above. (And no, I'm not going to read this thread either. I can barely load it!!)

Growler

Lawrence: I don't know my pcv was faulty. It was an option but on the other hand it was brand new. If oil level builds up in the cover to the point where it floods the breather, its starting point is the level of oil in the sump. If the oil is low to start with, it may not be sufficient to give it the "leg up" to flood. If full manifold suction is applied to a column of oil it would lift it much higher than the distances involved (30" Hg and about 30' of water is supported by a full vaccuum)

G Williams (Graeme)

Graeme, I believe you. I agree if the oil level in the sump drops, and then the sucking stops, the two must be connected in some fashion. But how? There doesn't seem to be a means for the suction to take hold of the reservoir of oil in the sump. And now you've complicated it even more, by saying something I deliberately left out. You think your PCV might be ok and not faulty at all. When it first happened to me, I was using a PCV. I thought it was faulty. I bought a new diaphragm and valve. It didn't fix it, so I changed to the Y piece, which also didn't solve it, the continous flow of oil continued. I also agree about the lifting capability of 30Hg, but there would need to be a sealed sump to even consider that wouldn't there? And it isn't seales. Air is fed in via the rocker cover cap breather, breaking the "vacuum". Yup, I've read that article and intend to read it again. I've seen similar before, but it doesn't explain the oil being sucked into the inlet in a continuous column of liquid oil. No I'm not disputing that an oil mist exists, or course it does. But it doesn't explain my symptoms (and some others), even if there is an element of oil mist involved, -- which there probably is. Sure, it's a long thread, and takes time to read, but unfortunately not reading it, means not knowing that all this has been discussed before. My breather is clean. But let's suppose it's not. Firstly, the breather cannister isn't FULL of wire mesh. The mesh only occupies part of it. Secondly, the mesh in occupying a portion of the breather cannister, reduces the volume of oil that could be "trapped" in there. Even without measuring it, I can see that the wire mesh won't hold at least 1/3rd of a pint of oil in mist form or otherwise. So where is the remainer of the oil coming from? It can only come from the timing chain cover. So is it now being suggested that mist droplets in the mesh, combine with mist droplets in the cover, to form "AT LEAST" 1/3rd of a pint of oil, and rise up the breather hose? Well it's a theory. OK, let's suppose it holds water(oil). "Typically the gauze in the separator becomes much reduced in efficiency after it has been dealing with a very tired engine for quite some time as it gets very gunged up doing so, but then gets no attention when the engine is overhauled." Absolutely. Most engines out there are running with old breathers, that have NEVER been cleaned even in petrol, let alone a chemical bath, and yet no oil sucking. Why isn't EVERY engine affected in exactly the same way? What's unique about mine and others engines? Nope, I still don't buy the oil mist theory to explain this particualr oil sucking thing, even though as I've acknowledged all along, it's involved in a small way.

Lawrence Slater

Where did this figure of 1/3 pint of oil come from? I think that the uncertainty throughout this long discussion is what amount of oil produces what amount of thick blue smoke. In my case I have had thick blue smoke belch out of the tailpipe and cause enough of a cloud that it would obscure visibility for any following traffic. And that I know was just from the oil mist / oil phlegm theory. Your problem if it is drawing up that much oil appears to be very different. But I believe that most other reports of significant amounts of oil smoke belching out are in reality the lesser form, basically as Chris has described.

Guy W

How much oil equals how much smoke ? Well I know that the neighbours house disappears from sight when I start up an engine after a wet compression test and that has 3 oil can squirts per cylinder so about a dessertspoon full in total. "Even without measuring it, I can see that the wire mesh won't hold at least 1/3rd of a pint of oil in mist form or otherwise." No it doesn't but that is not the way it works. What you get is a constant flow of oil and air/fumes up the separator and the associated pipework which accumulates into bigger and bigger "blobs" which being heavier than the mist have more tendency to stay in the vertical pipework and let the gases bubble through them - this accumulation carries on until there is enough oil there to travel into the carbs - then because they are now sucking on pure oil rather than gases you get a sudden rush which clears out the separator and all the associated pipework. "How do you explain that inspite of my cleaning my wire mesh with petrol several times it never solved the problem? I don't dispute the droplets of oil, slugs of oil, and mists of oil getting into the engine, and no doubt my engine suffers(ered) from that too, but what happens to my engines is in a different order." Petrol may wash out some of the liquid oil but it does nothing to shift the carbon deposits on the mesh. The only way I know to clean the mesh is to heat the whole unit red hot - then you will see the incredible amount of smoke that NO oil in the separator can produce! "Most engines out there are running with old breathers, that have NEVER been cleaned even in petrol, let alone a chemical bath, and yet no oil sucking. Why isn't EVERY engine affected in exactly the same way? What's unique about mine and others engines?" Because every engine is different - the amount of blow by the pistons - the amount of suction from the carbs or PCV - the viscosity of the oil - the state of the separator. On a engine that doesn't suffer the problem the separator is coping and vice versa. The solution is either reduce the suction from the carbs or increase the size of the separator - better still go for the vortex type oil separator used on the M series engines or on race cars - http://www.demon-tweeks.co.uk/motorsport/oil-catch-tanks/automotive-plumbing-solutions-lightweight-alloy-oil-catch-tank - fit a pipe from the bottom of the separator to the sump and you have a self emptying unit.

Chris at Octarine Services

Hi All, Lawrence, I think once an amount of oil has covered the base of the breather tube then the negative pressure from the carbs is easily enough to lift it to the carbs (doesn't matter at that point whether the rest of the engine is oil tight). Graeme is on the right track with this.. I know somewhere you mentioned the measurements of the negative pressure you had in the inlet. I think you can convert this to an approximate measure of how much oil this would lift relatively simply: Level of oil lift = manifold pressure (inch Hg) X Density of Hg (13500 kg/m3)/ density of oil (about 850kg/m3) or in other words for every inch hg oil will be lifted 15 inch. So manifold pressure 1 inch hg less than the crankcase would lift the oil all the way.. out of interest what pressure does the PCV block at.. Cheers Tim

T Dafforn

I would have expected that if as much as 1/3 pint of 20/50 oil were ingested into an engine, it would stall the engine. Yes, a petrol engine will "run on" on oil vapour from the breather system, but that, like diesel, is much more volatile than liquid 20/50. In fact with combustion chambers of around 24cc, that much oil is sufficient to cause a hydraulic lock - and probably end up with a bent con-rod!

Guy W

Guy, The drillings in the carb bodies will restrict the flow and the oil would be distributed amongst the 4 cyls so I doubt more than a cc or two would find its way into any one compression stroke.

Chris at Octarine Services

Well either I'm a fool, I'm a liar, or I'm exaggerating. LOL. I know I'm none of those. I know what solidified carbon deposits look like, and I know what sludge looks like. Neither were present in either of the timing covers on my engines when I rebuilt them. What oil "varnish" is present now, is easily wiped off, in seconds, with petrol. See picture. I see no reason why the wire mesh in my breathers would be clogged with carbon deposits either, and since I can EASILY pour engine oil through the one have off the engine, I'm confident it isn't clogged. History --- . I bought my sprite in 1977 with a running engine it. It rattled and it had low compression, but it went, and didn't smoke that much considering the siezed rings I found on the pistons when I stripped it. But although it dod smoke a but, it DIDN'T suck oil in the way I'm telling you here. A couple of years later circa 1980, I rebuilt it, using the SAME timing cover, which I would have washed in petrol, the same as everything else. I put it back together again, bored out to +20, new standard 4 ring pistons, ground crank, new standard camshaft and new cam bearings, standard cylinder head with the same valves. I can't remember if I used a new cam endplate. As soon as I started it up, and it got a little warm, it sucked oil into the PCV. Note: I used the same timing cover as prior to the rebuild, when it DIDN'T suck oil. After trying to "fix" the PCV, I changed to the Y piece. It still sucked oil on warm up. I endured it for years. I then bought ANOTHER running engine taken from a Midget that was being scrapped. I drove it, and it ran well, it didn't smoke, and it DIDN'T suck oil. I wanted it to build a slightly faster engine. So I stripped it, had the crank ground, the block bored to +30, and I used 19320 Cooper S type 3 ring pistons. The camshaft was a Piper HR270, and the head was from an Austin 1300GT. I put it together, and as described earlier in this thread, I re-used the camshaft endplate. I swapped out my original engine, and put this one in. As soon as it started to warm up, IT SUCKED OIL. It didn't suck oil BEFORE the rebuild, but it did immediately after the rebuild. SAME timing cover with the same wire mesh as was on it prior to the rebuild. After trying to find why, I gave up and again endured it. Years and miles later it was getting tired, and I rebuilt my original engine again. Cord rings new end shells, new standard cam on existing bearings. It still sucked oil until I swapped to an HIF, or the maybe the cords finally bedded in and reduced crank pressure. I don't know. It's still in my Sprite now. How much oil sucked up? Where does the 1/3rd pint come from? See my Post 02 March 2012 at 12:49:25 UK time, and look at the picture. I originally fitted that clear pipe in place of the rubber hose to see what was happening when I first experienced oil sucking. I could easily see when that pipe was full of oil. I've still got that pipe on my car. I can see if it's clogged with anything or not, and it's not. The volume of that pipe is enough to hold 1/3rd of a pint of oil when full. I've seen it FULL of oil on NUMEROUS occasions. Now look at the pics below again. I filled my timing cover today with oil, and then drained it into a pint glass. It too can hold about 1/3rd of a pint of oil. So with my breather pipe full of oil, AND the breather canister full of oil, my engine was being fed a continuous supply of oil from a reservoir of "at least" 2/3rds of a pint of oil. Now you tell me that "mist" in the timing cover condenses to form 2/3rds of a pint, and I say you're wrong. That would be a "very dense cloud" of oil not a mist. And once the wire mesh in the breather canister –- which can't hold that much oil --- was empty, there wouldn't be time to condense sufficient "oil mist" to immediately replenish the supply in order to form a continuous column of oil flowing to the carbs/manifold. Does the engine stall? Nope it doesn't. It keeps right on running. If you want to see how much smoke that produces, hear the engine note change, and listen to the loud clanking and pinking noises it makes, whilst watching liquid oil drip from the exhaust tail pipe, -- then disconnect the breather pipe from the timing cover, get a funnel, and pour 2/3rds of a pint into the manifold or Y piece with the engine on about 1200 rpm. Tim, I agree with both you and Graeme. The breather entry hole, must at some point be covered, and at that point, as Guy noted a long way back in this thread, the suction from the carbs increases dramatically. Enough to lift the oil all the way into the cars/manifold. What I was asking is, how can the oil level in the sump contribute to this? I don't dispute that it does, because I've experienced it too. But for a syphon to work on the sump oil, the pipe would have to be at the same level or submerged, but it's not. Are you saying that sufficient suction could "raise" the oil level in the sump, enough to lift oil out of the sump, into the timing chain cover, and up into the breather? I'm certain that something is causing overfilling of oil in the timing chain cover, and when the oil is cold/cool, it just can't drain out fast enough. It reaches the breather entry hole, the suction increases as a result, and oil gets sucked into the engine. Everything, crankcase pressure, suction, mist, splashing, etc contributes to it, but imho, the prime cause that tips the balance as yet hasn't been found. Nobody has the answer. On my engine it may be the cam endplate or the front cam bearing. I don't know. But it's more than "mist" alone. Yes it can be solved by reducing suction. This results in oil scroll leaks. Reduce blow by? Sure rebuild the engine again, and hope for the best. It hasn't worked on mine 3 times, but then I'm a fool. How about all the others who've rebuilt their engines, and although they didn't have oil sucking before the rebuild, they now have oil sucking. Are they all as daft and useless as me at building an engine? Fit a bigger breather canister, or a super-duper mark nine stronty valve, connected to a time vortex breather system. Yup could do it. But I'd like to find the cause thanks, and fix that. :). Tim, when are you putting your head back on, and connecting the breather to a PCV or the carbs? It's my guess that this will fix yours.

Lawrence Slater

LOL, I seem to have upset you again Lawrence! What I was asking, was how did you measure your 1/3rd pint? I couldn't visualise a practical way of measuring it whilst it was being drawn into the engine and burnt. To me, measuring the volumes of the chaincase, canister or hose is not the same thing, or at least is making assumptions which may not be true. With this being such a conundrum, you need to be open to all possibilities unless of course you are not really looking for new ideas. If you draw a mixture of air and oil up a plastic pipe, the oil will cling to the pipe walls as it is being drawn up the pipe. Cold viscous oil even more so. Seen from the outside this can look as if the pipe is solid with oil, when perhaps it isn't. You would still have significant oil sucking, but not the same volume. This could explain why an excess level in the timing chain could get transferred through the two high suction points first through the entry to the canister, and then through the entry to the breather hose. It doesn't solve your "why some engines and not others" question. But there may be a fairly fine "tipping point" in the quantity of oil needed in the chaincase to cause the effect. And this threshold could be explained by a sum total in the variations of oil temperature, viscosity, blow by and manifold depression etc between an engine that does, and one that does not. (This thread is still almost impossible to load!)

Guy W

Seems like for you the cause is rebuilding the engines - they don't suck oil when knackered but do after Lawrence has tinkered with their insides! Perhaps your shop that does the boring is not using a torque plate and the bores are oval? Or perhaps the bore finish is wrong? Maybe the bores are not bedding in properly? Cos it rather points to TOO much blow by the pistons.

Chris at Octarine Services

Lawrence: it doesn't need a sealed sump - that would stop it! Image a straw dipping into a galss of water. Suck on one end and the water rises up the straw. If there were a cover on the glass, the suction wouldn't do it. Relate the glass to sump, water to oil and straw to rubber tube from the breather, then the suction is provided by the inlet manifold. Here's some info on the pcv http://mgaguru.com/mgtech/engine/cv103.htm

Graeme Williams

While not quite pertinent as I used large bore breathers into a catch tank and no PCV my last engine, after full rebuild, chucked oil out initially into the tank after rebuild, even with a separator, but over the course of the first 100 miles it diminished to just passing some oil mist and no bulk oil into the catch tank as the rings bedded in. Breathers are 1" into the rocker cover and 1" to the separator at the fuel pump boss. The separator has a drain back to the sump with an anti-surge valve in the sump. Interesting at the time I noted that the new engine was using the oil cooler even for a trip of a few miles into Bath and back which after bedding in didn't even get the cooler warm. The system had an oil thermostat and this issue went away in the first 20 miles or so.

David Billington

After removing the pcv following the disasterous oil smoke on start-up, I ran the hose from the timing cover into a catchment bottle at low level (about where the shocker sits). Never a sign, or even a smear of oil in the bottle.

Graeme Williams

No not upset at all Guy. Just getting bored repeating all the same info over and over again, because my typing's slow. Also my mind is very open to new ideas on what's causing it, as long as we're discussing the same thing, and not mists and vapours. Sorry about the thread, others started typing in it again. lol. How did I know it wasn't just oil clinging to the sidewalls of the pipe? I pulled off the pipe at the breather and let the oil run back into a jar. There was loads of it. Even used engine oil clinging to the sides of the pipe doesn't make it the completely impossible to see through it. It was full, you'll just have to take my word for it. Yep you're right Graeme, if the sump wasn't open somewhere, the suction on the oil in the sump would be lessened I guess. But I just can't see the sump oil reservoir being lifted all that way. However, that doesn't explain why, when the sump level drops below max, the sucking stops. Now you have no suction at all on the breather. So apart from crankcase pressure, there's nothing to expel the oil, and if nothings coming out, there can't be much blow by. That removes blow by as a cause in your engine. As for mine Chris, so now you're accepting what I say, and attributing the cause to blow by, -- crankcase pressure. Of course there must be an element of that. I figured as much. But if that was the sole cause, and the bores were that ovalled, there'd also be a lot of smoke at all other times too, my compression and performance would be crap, which they weren't, and I'd be blowing oil from the dip stick. My engines, when not sucking oil, are smoke free. Here's something some may find surprising, I did. The mesh in the canister occupies less than 25% of the space. It sits in the centre, 45mm in from each end, and it's only 25mm deep. It's held in place by an identical metal spring(clip) at each end of it. So the very maximum amount of oil it could hold, if the canister is full, is less than 25% of 1/3rd pint. But of course circa half of the wire mesh is solid. So actually it would only be 12.5% of 1/3rd of a pint. Not very much oil at all. Probably enough to account for the "burps" of oil some get, but no where near enough to account for my engines symptoms, or to fill the breather pipe. It's a small amount of wire mesh. If it were full of carbon deposits, it would reduce suction and in fact limit the possibity of sucking oil I reckon. And if it needs replacing or chemical cleaning, why didn't BMC make it a serviceable item? It's not. I also filled the timing chain cover with water, - with the chain and sprockets inside. 1/2 a pint or thereabouts. So if it is full of oil when this starts, that's a lot of oil to draw on, and explains it nicely. The question remains, how is it filling/not draining?

Lawrence Slater

One quick and easy way of sorting out the liquid v vapour issue is to insert a short length of clear plastic (Makrolon?) tude into the flexible hose between the breather and the pcv. If it is liquid oil coming over it ought to be very obvious. Anyone have 150mm of thick walled 12mm tube to hand?

Graeme Williams

woo-hoo

David Smith

400 ps - my engines do not smoke :-)

David Smith

Lol graeme - that was done ages ago on the thread!!

Chris at Octarine Services

Lawrence, No I am just saying that excess blowby will push more mist into the breather and if the mesh can't catch it to return it to the sump then it will travel on up to the carbs. I am not talking a light mist though - with the crank throwing 7 journals worth of oil - that's 12 discs of droplets within the crankcase being thrashed round with 4 rods whizzing about as well, think more of a shower inside the sump area - plus the oil in the sump being whipped up (windage) by the whirling crank - if there is too much gas being blown/sucked through that hole in the frontplate then I can see that oil in the timing cover may build up because it can't flow against the blast!. Solutions? 1. make the hole in the front plate much bigger 2. weld a plate over the breather entrance hole to stop direct splash into the breather can and raise the entrance height. 3. Remove the front can completely and fit the side cover breather on the front tappet chest cover a la 1098 engines 4. Remove the front can and connect breather to rocker box cover a la 1500 engines. Number 4 would be likely the most effective

Chris at Octarine Services

Chris: don't remember that. Do you know who by, and the result?

Graeme Williams

Me Graeme. See my pics Posted 02 March 2012 at 12:49:25 UK time. I've had a clear breather hose since I first had this trouble back in the early 1980's. That's how I know it's liquid oil in a continous uninterupted flow. Chris. I've been arguing that the pressure coming from the crankcase, resists the flow of oil back into the sump, until I'm blue in the face. So at least we agree on that. No comment on the tiny size of the mesh, and the very small amount of oil it can possibly hold? I'll buy the splashing around of oil, definitely. I'm aware that happens, and it possibly also helps to explain why, if the oil level in the sump is allowed to fall to a certain point below max, the sucking stops. If the crank paddles aren't as deeply immersed, that might be the tipping point for that contribution. But it's no solution, to run around low on oil. On your list, 1, I assume you mean make the hole in the block face bigger. The engine plate hole is big enough already. This has already been discussed before too, and a little way back Fegus suggested it again. I asked if anyone knew if it would weaken the block much. We also discussed it on the other thread, "good news bad news". Guess you didn't read those posts. :). 2, would raise the entrance height, but prevent draining from the canister below that plate. And since I suspect the height the oil level actually reaches, inside the cover, is to completely cover the hole, I doubt it would work. It could even make it worse. 3, 1275's don't have tappet chest covers. Thought you knew that. But under consideration if the actual cause can't be found and rectified, is to fit a breather canister using the mechanical fuel pump blank. 4, tried that many years ago. Didn't work too well as it resulted in more rear scroll leaks. I assume that's why BMC abandoned it in the first place.

Lawrence Slater

I think where we differed is that you suggested the oil was entering the timing cover via the front cam bearing - I know the flow from there is very low ( having run an ngine without its timing cover in the past - very little comes from the front of the crank too. I think the problem is caused by the heavy oil content of the gasses in the crankcase coming through the hole. Normally the engine copes with that until the blowby or carbs suction get too great. Another thought is to fit a sump baffle to reduce the pick up from windage. Yes total senior moment there 1375s dont have tappet chest covers.... The 1500 was later than the 1275s and the rocker cover breather is often used by the racing fraternity. Actually the rear pump fitting would make a good vent point and being close to the scroll could be advantageous. Re the filling of the timing cover - it would be interesting to fit a sight tube to the cover - like they do to oil catch tanks - then you could actually see the level that the solid oil reaches.

Chris at Octarine Services

Chris. The 1500 and 1275's are different engines though aren't they. Triumph and A series, with significantly different designs surely and the 1500 was derived from smaller stable mates that'd been around since the 60's i thought. Anyway, the mechanical fuel pump on the A series, is nowhere near the oil scroll, it's on the left front side of the block. Yup the sight tube's been suggested. I'm hoping to fit an entire perspex window in the cover to see what's going on though. Round in a circle again. Did you read about my camshaft end plate in the early postings, and the most recent posts about it? VERY interesting that you say you ran an A series WITHOUT the timing chain cover. Wasn't oil splashed all over the place when you did this? You say not much oil came out from the cam bearing, but this is the supply to lube the chain and sprockets. The cam end plate has a hole for that purpose, which is fed via the groove in the cam front journal. Obviously it's supposed to be the correct amount of oil, and not too much. But how much is that? Nobody knows the exact amount. But if you've run an engine without the cover, and "not much" comes out, then my theory about over suppply from my leaky front cam bearing, via the knackered endplate, has a whole new lease of life and proves on my engine at least, what I've been saying all along. Namely the cover is filling to the point at which the breather entry hole is covered.

Lawrence Slater

Thnx Lawrence - sorry I missed that.

Graeme Williams

Well, I think it is interesting that Chris has run with the timing cover off and not seen vast quantities of oil being pumped out, while Lawrence got quite a bit of oil pumping out (even before warping the cam plate) when just turning the engine with a drill or by hand. (I think Lawrence's oil pumping test is in the "good news bad news" thread) Maybe there is a reason why some engines pump more out of the bleed hole than others? Charley

C R Huff

We ran the engine sans cover because we had a strange rattle from the front end ( engine still in car ) obviously without the rad in there we couldn't run it for long and it was only at idle. But there was very little oil thrown out onto the chain - certainly no more than you get when running the engine sans rocker box.

Chris at Octarine Services

Thanks Charley. Since nobody since nobody else commented, I suspect you are one of the very few who read that post, and looked at the picture. It was in THIS thread -- Posted 12 August 2013 at 11:24:19 UK time As you say charley, I got a significant amount of oil from the cam bearing and distorted end plate. So if the "normal" amount is as Chris describes, I've got 3 obversations. 1). How does the chain and sprocket get enough oil if there's very little coming out? I suspect that above idle, and for longer than a few seconds, enough does come out. 2). As I got a significant amount just be hand cranking, I reckon I got too much, and by the sound of it, way above "normal". 3). It may be as charley says. Some engines expell more than others from the cam bearing, and if so, why? So there's only one thing for it. As soon as I get my Midget on the road, I can take the Sprite off the road, and I'll repeat Chris's experiment. But if I can get some long rad sized hoses, I'll install the rad in a remote location and put an electric fan on it. Then I can see what really happens.

Lawrence Slater

As well as the cam squirt hole which fires oil onto the back of the cam sprocket, there is oil from the front main bearing which will get onto the crank sprocket - plus I guess the chain will pick up oil at the bottom of the timing cover.

Chris at Octarine Services

Yup I know that Chris. I was making the point that if hardly any oil came out from your running engine, how can the chain possibly get enough oil, when compared to my hand cranked engine which delivers quite a bit? I hand cranked for less than 20 seconds, and collected quite a bit in the tank below the chain. -- see picture in previous post. If that had been a running engine with the cover off, oil would have been thrown all over the place by the chain, the sprockets, and thrower on the crank. So what you've done, is to confirm my thinking that my engine is delivering too much oil into the cover. -- irrespective of the oil mist carried in by blow-by gasses, which only adds to it ---. That amount of oil, when cool, is too thick to drain away fast enough. The levels rises inside the cover until it reaches, and then rises above the breather canister entry hole. Then the increase in suction caused by this, lifts the oil all the way to the inlet. As the engine and hence the oil continues to warm, the oil thins, draining is sufficient, and the sucking stops. As long as the oil remains warm enough, no sucking, as soon as the oil cools enough, the sucking starts again. See my post in this thread from last year. 01 March 2012 at 23:30:46 UK time. As for what's happening in my other engine, that's more speculative, since I've only got my spare engine apart.

Lawrence Slater

Yes also explains the periodic puff that some have described.. perhaps in boarder line cases rapid deceleration using engine breaking (hence high revs) would push the oil over the breather: Braking forcing the oil to the front of the engine. High revs increasing the timing chain wave effect. Closed throttle giving max vacuum. the low engine load and high revs also gives max blow by potential (according the the 106 PDF). the perfect storm? Tim

T Dafforn

Maybe so Tim. I was about to say max suction depending on if connected on the manifold or the carb. But actually, when on the overun with the throttle closed, there will be max suction in the manifold, but as soon as you put your foot down, that's immediately transfered to the other side of the throttle. In my case --- before I fitted a Single HIF -- I changed from a PCV on the manifold, to the Y piece on the twin SU's. The episode I described in Andorra was on the Y piece. As soon as I put my foot down after going down hill for a mile or so, I started sucking oil. The engine temp had dropped to way below 140. So the oil was cooler, just as I exposed the timing chain cover to a sudden increase in suction. Of course people do do this in many cars, but don't suck oil. So I'm still sure I must for whatever reason, have too much oil in the cover. Dropping the level in the sump, may just tip it back the other way so sucking doesn't happen. But that just doesn't sound like the best solution. The must be something else going on.

Lawrence Slater

This thread was discussed between 16/02/2012 and 22/08/2013

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