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MG Midget and Sprite Technical - Manifold Gasket - to seal or not to seal?

Hi,
Can I pick your collective brains?

I'm fitting a Maniflow 4-2-1 manifold to my '75 1500.

Should I coat the new manifold gasket with any kind of sealant?

And is there any other dark magic I should know, now that I'm on the rebuild side of the job.

Thanks in advance

NigelB
N Broomfield

I’ve never used any gasket sealant on exhaust manifolds. I believe you can get some high temp silicone sealants for such things but I’ve never had a problem just using a new gasket.
John Payne

John,
Marvellous, thanks, I'll get started, and hopefully, finished today.
Thanks
NigelB
N Broomfield

Well I've hit another stop in work.

When I was taking the manifolds off three studs came out with the nuts and I can't separate them. The two short ones for the far ends and the furthest back top row long one. I don't know if they are all numbered.

I've had them soaking in release oil for the day and tried a blow torch and a vice but still no luck.

I can get the "outer exhaust manifold" for no's 1+4 held on with the front stud/nut combo but it means I can't get the rear one in with any confidence that I won't strip the thread. And vice versa putting the rear in first. I can finger screw them in without the manifold in place, a bit tight but I know I'm not crossing the thread just finger screwing it. But they won't start with the manifold in place.

One of the long studs needed the thread remade to get it to start into the head, again only by fingers.

So looks like I need three bare studs to screw in then put the gasket and manifold on then the nuts.

Oh well, it's not as if there's nothing else to do. Like bleed the brakes, fit the window inner felt weather strips, straighten the steering wheel, replace the outer door handles, etc, etc.
N Broomfield

Manifold studs on 1500 engines are pretty highly stressed, as they are on the straight six Triumphs. They certainly used to be notorious for failing.
Personally I might consider new ones. Rimmer Bros still have them; I got some last year for Don's GT6 to replace some very dodgy looking ones, along with some of the little bridge clamps he somehow lost.
I've never used anything on manifold gaskets and don't remember any issues. My old man used to use a light coat of grease which he reckoned "helps it burn in" but I never liked the idea and never bothered.
As John says a new gasket shouldn't give any worries.
A question though;
Do you have the steel manifold nuts or the bronze (??) deep nuts?
Greybeard

I have exactly the same setup, 1975 with Maniflow 4-2-1.


The Maniflow is a very tight fit, I ended up grinding some clearance on the flange of the chassis leg to give a bit more room.
Chris Madge

Greybeard,

Thanks for the heads up on the stress. I've tried gripping the long one in a bench vice, soaked in release oil, and it still won't budge. I feel that it will just snap before the nut moves. The short ones don't have enough blank shank to grip and will ruin the threads.

So new ones are on order, after search for someone who may have the studs and the nuts together.

Chris,

I think I'm going to have to grind a bit of clearance as well. When you ground the flange of chassis runner did it result in a hole that consequently needed welded?

Cheers guys
Many thanks
Nigel
N Broomfield

Nigel

No hole. Just a crescent shaped cut into the flange, the box section was untouched.
Chris Madge

This thread was discussed between 28/08/2022 and 01/09/2022

MG Midget and Sprite Technical index

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