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MG Midget and Sprite Technical - Maniflow Exhaust Hitting Chassis Rail

Just a heads up for Frogeye restorers (you know who you are):-
My maniflow manifold misses the chassis rail by about 1/16", and therefore clanks when the engine revs drop just below idle.
I've just put a 1/16" shim in the nearside engine mount, but I'm not convinced it's rotating the engine about the o/s mount - might even be just moving the engine over a bit and making it worse.
I suppose the other solution would be to create a little venturi by battering a dent in the manifold.

So, no real solution - just sayin' . . . . . .
Nick and Cherry Scoop

Off the wall ideas, you could try slackening the 4 gearbox mounting bolts and seeing if you can shift the drivetrain across a little that way.

I've always had the same issue with mine, the hole that the pipes go through was radiused back when I installed the thing and I'm currently running an engine stabilizer bar from a Mini going from top of bellhousing laterally to passenger footwell, helps a bit but doesn't cure it completely.
AdrianR

Nick, on my 'other' Sprite the Maniflow pipe tapped on the chassis rail when l revved the engine. I too have an engine stabiliser bar but also ground back a crescent shape out of the bottom flange of the chassis rail. That fixed it.
GuyW

My old Maniflow touched the cassis rails. I even had to bend the rails. The new Maniflow has another configuration The two tubes who were next to each other are behind each other now so no problems at al.

Flip
Flip Brühl

Solution i use is to mount the manifold in a mill and put a 5 degree angle on the flanges to swing the pipes closer to the block and away from the chassis rail.
Chris at Octarine Services

Interesting. My frog's Maniflow mainfold is a perfect fit in this respect. It even manages to miss the Shorrock (which the PECO variant didn't)
Simon Wood

I always thought thst the exhaust manifold was different for 948 and later engines. Is it possible you have manifold for a later engine/car?
G Lazarus

It's not the flange though, Guy, but the rail itself. I had my tools out to ease the 'floor' a little, when I noticed it was the top corner of the box section.




Nick and Cherry Scoop

I don't remember the details of my order, Gary, because I've had the manifold for 12 years, and I do remember packing the engine mount at sometime in the past. You've met her at least twice at Le Mans without the clatter.

Simon - it's not fair.

Chris - I wish I had a mill.

Adrian - bonkers idea; I like it.

Flip - you bent the structure to accommodate a manifold?!

I haven't had time to lift the front and go under to have a look, to see if my latest shim has worked, but I will shortly.
Nick and Cherry Scoop

I think I understand the advantage of a maniflow manifold but I have a question: In the 70's I acquired a 3 branch manifold (as it was called then) for my mk3 1098 Sprite. I changed the exhaust - could have been "Peco". I'm sure it ran better but that characteristic Sprite exhaust noise was lost. Maybe that was more the silencer thsn the 3 branch but, do you get a different exhaust note with a maniflow?
Bill Bretherton

I'm not sure there is an advantage with a Maniflow, Bill. It's one of the things I'm reserving for after Spridget 60 (if we get there) - to try fitting the much older LCB manifold that I have.

Even the smallest diameter Maniflow is too big for a 948, it seems. For engines short of racing spec., Vizard says that passage of exhaust gases from a 948 cylinder head into the vastly bigger caverns of a Maniflow is not so good - and others agreed on here. Willy was one, I think, and Chris from Octarine.

There's an archived thread on Technical called "More About Exhaust Manifolds".

If anyone's interested, my shims produced a clearance of 0.020".
Worse.
I took them out again, and still got nowhere near my 1/16".
I'll have to run the engine and see what it settles to, before I have any more ideas.
Nick and Cherry Scoop

Thanks Nick, I've looked through the archived thread. I think I'll stick with the standard manifold (already fitted) - the flow may be inferior but I know the exhaust will fit and there'll be enough power for my needs. And it will retain that Sprite "sound".
Bill Bretherton

Do you think I could persuade the maniflow to change shape a little? I thought of fitting the exhaust steady bracket (HUGE jubilee clip to get round the two pipes), and adjusting it to give a little push - say 1/16" - and then hoping that after a few good runs the hot manifold would accept the new shape. Then I could re-adjust to give it another little push.
Nick and Cherry Scoop

Nick - rather than do violence to the Maniflow you've got (which you could always sell on eBay): I believe they can do a repro of the Speedwell LCB manifold, where the centre pipe joins the Y-pipe from the two outer cylinders ABOVE the chassis leg:


Tom Coulthard

Not sure that pic makes it clear - there is only a single pipe going past the chassis leg (this is the original, from the illustration in the Speedwell catalogue):


Tom Coulthard

I think that Vizard discusses these and concluded that the LCB ones which is what l think yours is, Nick, are better for 1275 engines. The alternative, 3 into 2 into 1 like Tom's illustration are better for the smaller engine capacities.
GuyW

Nick l have just re-read your first message on this.

As the exhaust pipe is attached near to the top of the engine wouldn't you need to rotate the engine anti-clockwise (looking forwards) to make the pipe at the bottom move inwards, away from the chassis rail? That would mean adding shims to the off-side engine mount.

There may also be a degree of adjustment in the slotted engine mount bolt holes so you may get more clearance by levering the sump across with a piece of wood between the sump and the n/s chassis rail as you tighten the engine mounts up.
GuyW

Aren't all LCBs 3-2-1? I suspect the LCB as we know it - with the Y-piece under the chassis - scarcely existed in period. Clearly the Speedwell's CB is slightly more L than the outer primaries.

Almost all the period performance A-series manifolds were short-branch 3-into-1s, which is actually what Vizard compares to LCBs. However the usefulness of his conclusions are compromised by the text contradicting the diagram. (Uncorrected between the 2nd and 3rd edition.)
Tom Coulthard

No Guy - the chassis rail is inboard of the manifold. So I need to rotate the engine clockwise, looking from the cockpit.

Trouble is, the engine mounts are fairly vertical, so the rotation (if any) is cancelled out by the straight lateral movement of the engine.

Are there slots to the mount that fixes to the body? I must look.

Tom - thank you. That's a good solution, and I do actually have a Speedwell manifold or something like it. I fitted the Maniflow just because it fits with the exhaust pipe and was easy, and I was hoping to get to Spridget 60. As you can see here, the Speedwell is much shorter, and I would have to get a pipe made up to connect with the exhaust pipe, or buy a new exhaust.



Nick and Cherry Scoop

Have you changed/ replaced the engine mounts ?
Some i've seen are thinner than originals.
richard b

Yes, I have, Richard. I've replaced the steel/rubber/steel mounts, and that's my guess for the difference in clearance.
Nick and Cherry Scoop

Tom,
perhaps it wasn't Vizard. I would need to do some reading to find the reference again. Maybe it was Daniel? I would agree, both types effectively go 3-2-1 but the reference made a distinction with the LCB version and that one was better suited to the smaller engines. It was to do with exhaust gas pulsing and gas velocities.

Nick, yes of course. Brain disconnected!
GuyW

See small bore LCB:http://www.maniflow.co.uk/uploads/77469_8a899a083bd8292ce0011d3fd0e9d0ec.jpg

Vs

Large bore: http://www.maniflow.co.uk/uploads/17028_ce1b6ad6bef998d088c345429bc7e43d.jpg

Cheers
Mike

M Wood

Back to bodgers corner..add a 2nd manifold gasket?

I think if you want to change the shape of it you will need more heat than generated from running the engine. A skilled man with an oxy-acetylene torch can heat pipes to make them bend where he wants them to without much mechanical effort.
AdrianR

You could put a slight angle on the manifold flange face by careful use of an angle grinder and then trying up with a flat bastard file.
GuyW

Re period LCBs. About 40 years ago I bought what was described as a genuine works LCB. It was small bore, with integral inlets for H1 carbs. I mated it to stainless pipes and the standard silencer. It made a LOT of noise, to the extent that I was stopped by the police on the South Circular (they let me off). I since read that these sold well in period largely because of the noise. The centre branch was very long, but I don't have the measurements and I sold the item last year.

Vizard seems to have changed his tune over the years (pun intended). My 1980s edition of his book recommends a medium bore Maniflow for a big valve 998, which is what I have. The sound is gorgeous, not as loud as the 'works' system. I still have stainless pipes and the Maniflow rear box (which rusts madly and I have to keep welding it). Tricky to fit and the tailpipe is sited inboard of the rear bumperette not outboard as standard. There is about 1/8" clearance to the lower mounting of the telescopic rear damper, but it all seems to work without clonking.

When I bought the car a PO had cut the fillet that goes between the chassis rail and the suspension structure and bent it up, presumably to accommodate an aftermarket manifold, although the car had a standard one at the time. I welded this back down and it clears the Maniflow LCB quite easily. I have a good half inch of clearance between downpipes and chassis rail.

One problem is that Maniflow really only make manifolds for 1275s and with the lower deck height on a small bore the outlet is too low. I was hitting speed bumps. I got them to shorten the downpipes and it's fine now. I must say Maniflow is a very customer-focussed company - they put my car up on the ramp to get the stainless pipes to fit, at no extra cost.

Les
L B Rose

Just for info, I've managed to get packers under the ditchside engine mounting, and now have what I hope will be an adequate gap (though no more than 1/8"
Nick and Cherry Scoop

Nick – I am told there are still OE NOS engine mountings to be had – as the Spridget ones were also used on the Minor and its earthly reimbodiment the Marina:

www.ebay.co.uk/itm/Austin-Morris-Marina-MG-Minor-Wolseley-Sieries-front-Engine-Mounting-New/270656680447

Though these look little different from modern repro, they are stamped with the Patent no. 431874, a licence for which was issued to the Austin Motor Company on 9 Feb 1937 (!!). I was sure I had a pair somewhere but can’t currently find them ... (I do gather that, though fiddly, it is possible to swap engine mounts without taking the engine out – though I’ve never tried myself.)
Tom Coulthard

Tom

I think you’ll find that the Marina mounts were considerably different to the Minor/Spridget mount, with the possible exception of the 1098cc van/pick-up.

I believe they were used on the ADO16, however.

I bought some engine mounts from Unipart at Cowley back in the ‘90s. They had a little Firestone ‘F’ moulded into the rubber.
Dave O'Neill 2

Dave - I have already found, thank you, that Marina engine mounts with that patent no. stamped into the metal backing plate are indeed Spridget-identical. I would not have made this suggestion to Nick otherwise.

You seem to know they were for the 1098cc van/pickup, so what is the problem? Of course there are other Marina engine mounts - the range used 7 different engines - but they mostly look quite different.
Tom Coulthard

I tried packing under the rubber block, but the angle was wrong to rotate the engine effectively. It tended more to push it sideways, making my predicament greater.
But packing under the lower mounting bracket does the trick. My exaggerated scribble shows the angles.


Nick and Cherry Scoop

I don't know, just wondering, could the patent number apply to more than one part (number). Could it apply to part of the part or an assemble process.
Nigel Atkins

Tom

There isn’t a problem, I was merely pointing out that the vast majority of Marinas didn’t use the Spridget mount.
Dave O'Neill 2

Well done Nick.
I must admit that is where I thought you meant you had tried the packing washers when you mentioned your first attempt. I wonder if a similar washer under the upper bracket to chassis bolt on the other side might rotate the engine a bit more and further increase your 1/8" clearance.
GuyW

Dave – as I understand it, the art of truffling for NOS parts is to find the obscure model or sub-type, where parts were still required to be on the shelf but were very slow sellers. Hugely popular models like the 1100/1300 range tended to mop up the supply of genuine parts quite quickly and owners were left with – as many of us saw it then – Quinton Hazell rubbish or later Unipart absolute cr*p. (Of course, by the standards of some repro parts available now, both companies were paradigms of engineering excellence.)

Nigel – you may well be correct but I think you miss the point. I was not saying that the patent no. identifies the individual part, but that it does indicate it was produced under BL’s auspices. I suspect the patent licence (obtained from the Standard Motor Company) may have been to do with the metal/rubber bonding process – a process that is reported to be failing on some repro engine mounts.

Les – by ‘period’ I meant period for the frogeye, when it was still in production or shortly after. The world was very different by the time BMC launched its Special Tuning Dept in 1964 (from whom your manifold could perhaps have originated?). Between 1960 and 1964, the number of cars on British roads QUADRUPLED – and to entertain these millions of new motorists came an explosion of motor accessories and go-faster bits that simply hadn’t been around before.
Tom Coulthard

Tom, yes I was thinking of the metal/rubber bonding process just wasn't sure which of the Frogeye/Spridget/midget range the mounts fit.

Your method of finding these original NOS parts is spot on and well done on making the match.

With takeovers, mergers and totally going out of business, and even before, the same part can have different codes or numbers and not just car parts.

Companies cross reference databases seem to have more errors and omissions now as suppliers and sellers seem to use databases from others replicating and even expanding the numbers of errors and omissions.

Getting any parts that you've not seen or had your hands on is a bit of a gamble.

Interesting statistic with the rise in cars between 60-64, one I never knew, must have been madness in some cities and towns.

Nigel Atkins

This thread was discussed between 26/06/2018 and 09/07/2018

MG Midget and Sprite Technical index

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