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MG Midget and Sprite Technical - valve rocker adjustment

I am trying to adjust valve rocker according to manual check all valves when othe valve fully open. how do i make valve 8 fully open to check valve 1 and then get valve 6 open to check valve 3. Oh. . . and what order do they number the valves. . confused!
d j kirk

D J. Number 1 valve is the one right at the front of the engine and so on back to number 8 at the very back.
Using the rule of nine as you are already doing, Adjust number 1 valve when number 8 is fully open. ie pushed fully down into the head. Best way to open and close the valves is to take out the spark plugs, put the car into top gear and roll it forward bit by bit until you get the required valve open. You'll see that as a valve is fully open, there is another valve almost open so when that valve opens adjust the corresponing valve. 5 closed, adjust 4. 6 closed, adjust 3 etc. Hope this helps.

Bernie.
b higginson

there's a John Twist video, see - http://www.youtube.com/user/Universitymotorsltd#g/u

or it's in the owners Handbook :)
N Atkins

Save you rolling the car back and forth. Remove the plugs as said, then apply pressure to the long side of the fan belt and use a fan blade to rock engine back and forth.

Also you can set your tappets in pairs. You will notice when for example when #1 is rocking (fully open), that there will be another almost rocking too. After setting #8 (Paired to #1), you will only have to turn the engine fractionally to fully open the next valve, and adjust it's pair.

Without my rocker cover off, I'm afraid I can't tell you which though. But it will be pretty obvious when you look.

It just saves a bit of effort and time in turning the engine.
Lawrence Slater

This was posted recently by Chris at Octarine Services - I think it's what Lawrence was on about.

"Here is a procedure that basically cuts the time in half to adjust all the valves.
An easier method to adjust valves, that requires less stops to rotate the engine is to use the following method:

Adjust valves 1 & 3 with valves 8 & 6 rocking*
“ ” 5 & 2 “ ” 4 & 7 “
” “ 8 & 6 “ ” 1 & 3 “
” “ 4 & 7 “ ” 5 & 2 “

*Rocking - valve 8 just past wide open and valve 6 just approaching wide open."
R G Everitt

Thanks RG, that's exactly it. My compliments. :)

BTW, I read recently that some advocate 12 thou cold and some 12 thou hot.

What's the concencus here? I've alway been a 12 thou coldy meself.
Lawrence Slater

I've always done them cold at 12 thou, which is standard procedure, but hotter cams require wider gaps.

Bernie.
b higginson

Whatever happened to Chris at Octarine Services?
Gary & Gaps

On a related point (and following on from Bernie), I have a Peter May billet 270+ cam in my engine. I assumed that I would need wider clearances for this cam (described as a 'rally' cam by Peter) and set them at 15 thou but when I spoke to Peter he said to set them at 12 thou. I don't want to question someone with the experience of a Peter May but is he right?
Chris H (1970 Midget 1275)

I would say he is right Chris

Even with very hot 286 road cams I still used 12 thou without issues. I always took the view that lift cost money so why adjust it away. :)

The very worst thing that could happen would be a burnt out valve but that never occured
Robert (Bob) Midget Turbo

One thing to keep in mind is the wear on the rocker face. If you use standard wide feeler gauges, this will give incorrect adjustments if the rockers are worn, as they bridge the indentation. If you can find a set of gauges that are the width of the vavle stem you will get more accurate adjustments. If you know any ex BT exchange maintenance engineers they may have a set.
Cheers John (ex BT)
HALL JOHN

Good call John Hall.

I slimmed down a couple of blades from my set for that very purpose, as I was/am too tight to buy new rockers. A bit of a bodge job, but it worked. :)

Better to buy properly made slim feelers though. I didn'y know BT engineers used them. Is this for contacts in exchanges or something?
Lawrence Slater

if the rockers are worn that much, time to buy new rockers!
David Smith

The main thing about clearances is that when the clearance is taken up the cam is still on its opening ramp and hasn't started to accelerate hard. If it doesn't take up till after the opening ramp, rapid wear will result. 12 thou on a midget cam is right on the sweet spot. Opening ramps can vary between cam profiles, hence some stipulate different clearances.

Paul Walbran

Presumably, if the gaps are set larger, say 15 thou, then this will also retard the valve timing and reduce performance? Would it be by much? (standard cam).

Yup David, but like I said, I am/was too tight to buy new rockers, and the car drives pretty well with the worn ones.

I doubt I'd notice the difference with new ones, unless it went on a rolling road to look for an extra tiny bit of hp.

I also have 2 sets of spare "worn" rockers in my garage or loft, so I'm good till I die, as regards rockers. lol.
Lawrence Slater

As I'm listening to AC/DC as I read Lawrence's reply, I say 'long live old rockers'!!!
Chris H (1970 Midget 1275)

And how about Led Zep and Judast Priest then?
Lawrence Slater

Actually, I've changed my mind about old rockers. I've just been out to the garage to re-adjust my rockers to 12 thou and one of the nuts stripped! Fortunately the adjusting screw seems OK and I have some spares nuts but I thought this a bit worrying and I hope this is not a common failure. I'm always careful when tightening so as not to over-tighten and I use a very short spanner. I guess its just old age (I know the feeling).

Chris - me nuts are failing - Hasluck
Chris H (1970 Midget 1275)

I listen to Bill Haley and Little Richard whilst doing my tappets. Now that's old! But then, so am I. LOL.

Bernie.
b higginson

must get confusing when rock around the clock comes on
N Atkins

Lawrence, you wouldn't believe the number of types and sizes of gauges used on the old electro mechanical equipment. I kept all mine and they have come in really useful over the years. I have a cranked set ranging from 1-60 thou in 1 thou steps, plus lots of others.
Cheers John
HALL JOHN

Why is the pitch on the rocker adjusting screws so coarse? It would seem to me to be the ideal application for a fine pitch thread to give more precise adjustment.
Guy

Old tools from bygone eras are the best.:)

Guy, maybe the thread is so coarse as fine adjustment is not really needed?

Actually, I'm coarse too as a matter of fact. :)
Lawrence Slater

Hi Lawrence

Having wider gaps makes the cam act milder as the valves close earlier and trap more air/fuel in. You are reducing the valve lift and duration which lowers the valve/time area. On our new rollers we can measure the difference in power production when running the tappets looser or tighter. Run them too tight (especially exhaust) and you lose power everywhere as the ex valve overheats...valve on seat time = cooling. Too loose and you can damage the valve tips. The initial ramp on a cam takes up the gap gently before the onset of rapid acceleration, if the valve tip is hit during the high acceleration phase it batters it rapidly. It also settles the valve back on the seat gently when set correctly. As a rule of thumb we tend to run ex tappets a little loose and inlets a little tighter. EG hot settings on a typical 12 thou cold A series cam would be 10 hot inlet and 12 hot ex. These could well be 12 and 14 respectively when cold.

Peter
P Burgess

Hi Peter,

Thanks for explaining that. I'll experiment. :)

Maybe one day, when I am flush, I'll take a trip up to your rolling road, and you can tell me hp wise, how much the fast road head I got from you has done for my Sprite. All I can say is that I can feel it has definetely add some, however much that is, and I'm happy enough with it :)
Lawrence Slater

And the "two valves rocking" method doesn't work with high lift cams. Try it, and then check with rule of 9, you'll see what I mean.
Alex G Matla

Have to take your word for that alex, as I only have a standard cam in mine.
Lawrence Slater

<And the "two valves rocking" method doesn't work with high lift cams>
It's not the high lift that's the issue, it's longer duration and/or the phasing, which might extend the opening or closing ramps into that zone. Usually such cams come with high lift, however there are also some short duration high lift cams for which this wouldn't be an issue.

Another cause of this is a poorly centred camshaft, in which the base circle is ground not concentric with the camshaft journals. I have seen base circle runout, as it is known, of up to 6 thou - some from reputable cam manufacturers/grinders obviously having an off day. I even found a few thou on a brand new standard factory camshaft (not all, just the one).

When you consider that even a very ropey cam profile, say 330 (crankshaft) degrees duration, would still have about 150 degrees of clean base circle around the back of the cam, and that the difference between full lift positions is very much less than that (typically around 30 degrees) base circle runout is likely to be the most common cause of the two valves rocking method giving an inconsistent result.

For that reason I check every camshaft to see if the two valves rocking method can be used - it does save a bit of time if it can.

(Here's the maths if you want it:
330 degrees duration
50 degrees opening ramp
50 degrees closing ramp
total 430 degrees
These are crankshaft degrees, so 215 degrees on the camshaft.
The rest is base circle: 360-215 = 145 degrees)
Paul Walbran

I tend to use rule of 9 for a 4 cyl a or b series engine, then start the engine, then chase any rattly tappets using a sacrificial 10 or 12 thou feeler gauge with the engine idling. On a B you can chase the noisy ones for ever it sometimes seems.

Peter
P Burgess

Hi pete,

I did try the running engine method once or twice, but the oil splashes everywhere that I had to clean off, made me lazy, so I went back to cold stationary engine.

btw, are these adjusting tools any good? I think Halfords used to sell them, but I never tried them.
Lawrence Slater

We had a customer show us how the tappet adjuster worked but I am not impressed enough to track one down :)

If the idle is low enough you shouldn't have too much oil splash, but Midgets can be little so and sos with a little rocker shaft/bush wear and have copious amounts of oil sploshing about.

Peter
P Burgess

Having read through this thread I would like to ask how much time could be saved by setting up the engine 4 times and setting 8 tappets using the rocking valve technique. As opposed to doing the job correctly and use the rule of nine! I reckon you would save about 10 seconds which is frankly worthless when compared to a job done right.

Peter I have noted in the past your comments on cooling the exhaust valve by opening the valve clearence to allow the valve longer on the seat.???

Whilst this would work and someone using say a 276 would gain a little benefit what about those of us using 286s and above? If a 276 exhaust valve requires extra time on the seat to cool what do we do with warmer cams? do we simply overheat? or is it god help us?
Robert (Bob) Midget Turbo

Not much time saved, just a bit of effort, for the lazy, -- me. :)
Lawrence Slater

Hi Robert

It is irrelevant what cam is used in relation to ex cooling. The tighter tappet settings than standard allow the valves to get too hot, stretch and spend even less time on seat, a vicious circle. Having the tappets set to a cold setting when hot seems to obviate the problem. Testing tighter tappets by starting engine and checking tappet clearances the clearances started to disappear as soon as engine started whereas the 'looser' by a few thou setting showed no loss of clearance under same conditions.

Of more interest all the engines seem to show more average bhp and torque with a slightly loose setting of inlet and exhaust on the new rollers even if a little drop in max bhp may occur and, as you know, it is getting out of the corner or off the line that is most important....torque means prizes :)

Peter
P Burgess

This is the adjuster brought out in the late 60s.
http://www.ebay.co.uk/itm/SPQR-VALVE-TAPPET-ADJUSTER-MINI-CLASSIC-BIKE-TOOL-BSA-TRIUMPH-gunson-ClikAdjust-/380379346846?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item589060379e.
Gunson also do one called the clickadjust.
Both designed to take into account any wear in the system.
Cheers John
HALL JOHN

Hi John,

Yup that's the one I remember. Are they any good? How does it work anyway?
Lawrence Slater

I think the MGOC have been selling them for years I think, £36 I know as I thought of getting one

but I think Peter said he didn't like them(?)
N Atkins

Expensive Nigel. Better off with feelers then.
Lawrence Slater

Thanks Peter but I am not sure what you exactly mean? maybe will get an opportunity to discuss it more with you sometime.

By the way not sure torque wins prizes?

Fred Dibnah's traction engine had far more torque than Jenson's McLaren but I know which one has a better chance of winning the Indian GP.

Fact BHP wins races, Torque times RPM equals BHP!
:)
Robert (Bob) Midget Turbo

This thread was discussed between 22/10/2011 and 28/10/2011

MG Midget and Sprite Technical index

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