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MG Midget and Sprite Technical - Maniflow manifold fitting

I am fretting about the fit of my Maniflow manifold on the 1275 Sprite. I fitted it last year to replace a 15 year old Maniflow that had eventually rusted beyond repair by patching. The new one is ok, but extends further below the chassis rails than the old one. It gives me very little ground clearance, especially as the car is also lowered.

The gap between the top of the pipe and the lower edge of the downwards facing flange is now 1 1/4" , which I think is around 3/4" too much. I can only think that Maniflow have altered their design as I am certain the previous one was very much tighter under the floor of the car at that point.

Options seem to be to try and raise the engine a bit - new engine mounts and maybe some packing. Or to cut and shut and reweld the new manifold down pipes.
GuyW

Guy. I too bought a new Maniflow for my 1098 Sprite and I am in the same situation as you. Also, the shorter 1098 block means that I have even less ground clearance. With my previous LCB (not a Maniflow one) I did as you are thinking about doing,ie cut and shut welding job. The Maniflow's pipe orientation as it passes through the chassis is different to the old one and it looks like with a cut and shut it would be quite difficult to correctly realign the pipes.
If you decide to do a cut and shut, I would be very interested to see how you did it as I am a bit concerned that I am going to damage my new(ish) manifold.

Bernie.
b higginson

Alignment is definitely the problem - plus getting a good enough weld bead all the way round. Access between the pipes may be awkward. I do have a spare head so would bolt the manifold up to that as a jig whilst welding.

But I am not sure yet.
GuyW

Welding the pipes can be awkward whee they are close together. When I was racing my A35, LCBs weren’t readily available, so I had to fabricate one from bits of Mini and Spridget LCBs.

I only had an arc welder in those days. You might stand a better chance with a Mig.

Packing the engine mounts won’t be easy, due to them being angled. Any packing will move them closer together, so they won’t line up with the front plate.

Have you spoken to Maniflow?
Dave O'Neill 2

Interesting, I purchased a new Maniflow last year. It replaced an ST manifold which I had had acquired in a job lot of Special Tuning bits when a BL dealer closed down in the 80's.

The Maniflow was actually closer to the chassis rails than the old ST one and I have as a result enjoyed better ground clearance!!
Bob Beaumont

I've considered doing this on my Sprite but never got round to it. I might do it to the Peco manifold I'm fitting to the midget but it will be slightly easier as it only has one tube from a triangular collector under the carbs.

The way I'd do it is scribe a line an inch or so longer than the amount you intend to remove at the chosen point, as straight and parallel as you can get it. Wrap tape round the tube as accurately as possible to give a straight cut line as you hacksaw. Cut the required amount out. Then hopefully after a bit of dressing with a file you can use the scribed line to line up the joint. Then I'd MIG round the join using small, quick spot welds. These would then be ground flat and I'd use a piece of larger tube about two or three inches long, opened up and wrapped round over the join. Then fully weld round the ends and opened up seam. Not easy to explain but hopefully you get the idea! Don't blame me if it doesn't work!

You could even do the tack welding when fitted to the car to be sure it's lined up as you want.

I'm actually quite impressed with the Peco manifold. It probably doesn't flow as well as a full LCB but it's a good compromise and fits perfectly through the unmodified aperture in the shell/chassis.
John Payne

Depending on how much you want to remove you could use an exhaust pipe expander and make the lower section a slip fit over the upper section and either weld or clamp. The vertical section of the LCB looks like a likely spot to cut for such a mod. Exhaust pipe expanders are available from the likes of ebay for less than £20.
David Billington

That's a good idea David. I would feel happier doing that.

I do have another possible alternative. Anyone remember Mike the Pipe? Well not far from me I see a van parked up that from the advertising do bespoke pipes like that for motorbikes. I don't know him but might see if I can track him down.
GuyW

Mike the Pipe was not far from me in Carshalton. His stuff was legendary! The current owners of the site still fabricate bespoke exhausts
Bob Beaumont

That pipe expander sounds like a decent bit of kit. I could do with something like that to make a new system for the Sprite. Looks like another toy for the toolbox!
John Payne

I guess this is what you mean David?

http://www.ebay.co.uk/itm/3PC-Tail-Pipe-Expander-Muffler-Exhaust-Tail-pipe-Tube-1-8-to-3-1-2-Auto-Tool/122835950174?hash=item1c9997da5e:g:0b8AAOSwgmJXzSsi

Worth a try at that price I think.
John Payne

John,

Exactly what I had in mind and lots being sold on ebay and at the price likely worth a punt. I did think that if the amount of tube from the LCB removed was small then the expander could be used on another length of the same sized tube to form a sleeve around the join.
David Billington

Mine needs to be shortened by 3/4" to 7/8". That amount of overlap would be ample for a welded joint, though probably not sufficient if one was just relying on a clamp.

Has anyone actually used one of these cheap eBay pipe expanders? I find it hard to believe that a 1.5 or 2mm thick walled steel pipe will actually stretch that easily with a simple expander like that. Do they actually work?
GuyW

Guy,

I haven't experience of those units but have stretched and shrank, a sizing operation, a number of parts over the years with simpler tooling and the sort of thickness you mention, it's not difficult. The material whether mild steel or stainless is quite ductile and stretches easily.
David Billington

I might try that then. Looking at the way it works I think if only inserting the expander part way into the pipe (say 3/4" in my case) one would need to restrain the segnments from expanding and popping out at the opposite end. Maybe fit an exhaust U-bolt clamp around it at the outer end.
GuyW

Guy,

I was thinking that myself as a possible issue with a short expansion length, maybe just pick up another section of the same steel tubing and use that to support the other end so the load is evenly distributed.
David Billington

Yes I must admit I’m a bit dubious as to its ability to expand a steel pipe that much. Obviously there must be a way of doing it as you see it on exhaust system but I thought it was done by forcing a mandrel in with hydraulics. Still it is sold as being able to do it so hopefully it will.

I’ve thought of a modification to my cut and shut method. Get some tube with the same ID as the OD of the manifold pipe, once you’ve cut the manifold, slide a 2 or 3 inch length of the lager bit over to basically create the same as expanding it. Then weld it all up, job done!

John Payne

Bernie, out of interest which one did you buy as the Maniflow site suggests the small one for the 1098 whereas most places seem to suggest using the 1275 one.

Trev
T Mason

Trev. I got it from Moss and I guess it must be the one for the 1275.
Do Maniflow recommend the smaller one for ground clearance issues, or is it because they feel it's more efficient gas wise?
Either way, it's worth thinking about.

Bernie.
b higginson

If you have friend with a tig welder, the pipe isn't too dificult to shorten and weld up. Mild steel and pulsed TIG works really well.
R Cohen

Bernie, I don't know if it gives better ground clearance or not. I think the pipe configuration is slightly different and its smaller bore but that's all I know. I seem to remember Vizard stating that the smaller bore gives the best performance but not read it lately so could be wrong. I keep wondering which way to go as I need to get one soon.

Trev
T Mason

I just spoke to Maniflow and the guy said that if I send my manifold back to them, they can tweak it to get better ground clearance.
I don't know what they will do other than bend it somewhere.

He also said that the 1098 one does indeed give better clearance.

He mentioned that 5 speed boxes alter the orientation of the engine. I was already aware of this, hence the spacer under my gearbox mount.
b higginson

I have had this Maniflow for around 12 months so I don't think I can expect them to alter mine now. I was also aware of the T9 thing and my home made gearbox support already lifts the gearbox as high as the air duct under the battery tray will allow.
GuyW

Just a follow up on this thread, and the suggestion of expanding the manifold pipe to aid a small cut and shut job to shorten the vertical part of it.

I bought one of the pipe expander kits off e-bay (£16) and tried it out tonight on a spare length of similar diameter mild steel exhaust pipe. pipe was 38mm with a wall thickness of around 0.7mm. Conclusion? - about as much good as those other "expander kits" advertised on eBay! (not that I have tried them, I should add!)

First I tried it cold, and couldn't get it to do anything measurable. Then I tried heating the pipe which was marginally better as I got a 0.25mm increase in diameter. Not enough to sleve the pipes together though. That was heating it to cherry red with a propane torch. I couldn't get more heat into it as it was convecting / radiating the heat away too much. Tightening the expander as far as I could at which point the expander bolt thread began to distort.

So as far as I am concerned, it is rubbish and doesn't expand pipe. What it will do is re-round a pipe, or push dents out. It will also expand if a slit is put down the side of the pipe, which I guess is what I will be doing, and then welding it up again.
GuyW

Guy,

I bought one and tried it and it was harder than expected but I was trying it on 16swg tube, a bit more than double what you have, as that is what I had, I got about 0.5mm expansion before thinking exhaust tubing would be easier. One thing I did do was I lubricated the thread and taper/wedge components as they seemed to come dry, I think that helped somewhat.
David Billington

Guy if you know the OD of the pipe you want to cut and shut you could try your local exhaust fitters. I sometimes make up systems or part-systems using scrap exhaust parts that I get from the local place. They are very generous and just let me help myself to bits and pieces. I'm often lucky and find bits in really good condition.
A short end the right size to make a welded sleeve over the cut would get you going wouldn't it? Short enough and you could probably get access to weld the cut first before sliding the sleeve over it and welding round it.
Alternatively, can you grind out the weld at the flange, push the shortened pipe through and reweld it (at whatever new angle you like for the clearance)?
Of course I can't see the job, so I may be talking b****cks!
Greybeard

Yes Grey, thanks, I do have other options. I just thought I would report back on the performance and limitations of the expander in case anyone else was considering one.

And David, yes I did lubricate it with a bit of graphite grease as I thought oil would run off as I heated the pipe. The other thing - they provide spare 0 ring rubbers, used to hold the spreaders together. Why ? - because they instantly melt and disintegrate when heat is applied!
GuyW

Glad I didn't buy one then!

I did my cut and shut job the other day but it didn't need a full cut. I found the manifold was angled down and also towards the sill. I cut slots about 3/4 of the way through the tube in a few places, bent it until it was about right and then welded the cuts up. Not particularly pretty (had to do a fair bit of grinding!) but it's not visible.

I then bought a 45-50mm adjustable pipe connector (about £10 on eBay and comes with clamps - excellent bit of kit) to join the 45mm manifold to the 45mm system. The system I bought was the Moss GT performance system in stainless. I'm really happy with it, so much better than the Maniflow one from a looks, quality of build and fit point of view. Whether it flows as well doesn't really matter but as both are just basic straight pipes and a straight through box I can't imagine there's much difference. In the Moss sale it was a lot cheaper as well, stainless too.
John Payne

John the car I am having to alter my Maniflow manifold for has a stainless steel exhaust system with a box transversely across the back. I fitted in in 1997 and have done around 95,000 with it since then I admit it is getting a bit ratty now and has had a couple of minor repairs but I think that is pretty good going. I've had mild steel ones fail after about 3 years and a fraction of that mileage.
GuyW

You've definitely had your money's worth out of that Guy. I can't see mine reaching 95k miles, not while I own it anyway!
John Payne

""I am fretting about the fit of my Maniflow manifold ..which extends further below the chassis rails and gives me very little ground clearance, especially as the car is also lowered""

Just to complete his story - I cut sections out of both the down pipes, splayed the end of the lower portion in each case by making 2 short slits in the sides and rewelded. The join for the outer two branches is where they come together so is not discernably different from the original. The other pipe now has a slight pythonesque bulge mid way down.

Fit is now much better with sufficient clearance, but no more than needed, below the floor pan.
GuyW

Guy - earlier you were worried about getting a good weld bead all round. Did that go OK? Should I particularly worry about a mig welding job on an exhaust manifold?
Nick and Cherry Scoop

Nick, the weld went fine, using my MIG. I don't see why it shouldn't last. It certainly loked OK to me.
GuyW

Thanks Guy. I'm glad to hear it, as I shall attack my old manifold as soon as the bad weather gets here.
Nick and Cherry Scoop

Nick, I am feeling in a generous mood - you can have some of my bad weather if you like.
GuyW

This thread was discussed between 23/04/2019 and 13/06/2019

MG Midget and Sprite Technical index

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