Exhaust - Sealer on gasket between manifold and downpipe?

[Zeus]

Hi all,

Fitting a new club shop supplied exhaust to my 1500 Spitfire. Should I use a bit of exhaust sealing paste on the gasket that sits between the manifold and downpipe assembly?

BTW - This is the 3rd exhaust purchased, the other two went back as they wouldn't fit the car!. Bends were simply wrong - How hard can it be?

Zeus

[Clive]

The 1500 has a major issue with manifold to downpipe gaskets blowing. Sealer is not really the answer. 

Ideally you want to file the mating face of the manifold flat, that invoves taking it off and removing the downpile studs, which need to be in very good condition. If it all looks ok, ignore that bit! (but many are lumpy)

Long brass nuts are useful too, do not use steel. 

Check the new exhaust mating face has no bumps etc on it too. 

[Zeus]

Thanks Clive,

Even the club shop supplied exhaust (which has all the right bends in all the right places) has a warped manifold flange on the downpipe. A straight edge reveals about a 1mm bannana bow. I guess the flanges get distorted when the two pipes are welded to it and no attempt is made to correct this afterwards. Perhaps I am picky but I don't think a gasket is likely to absorb that and the nuts/studs are surely not strong enough to straighten out the flange.

I have dressed it up and now I think it is pretty flat in all planes so I'll fit it without sealer on the gasket. The manifold is pretty good and I fitted new studs a while back.

fingers crossed.....

Zeus

[Clive]

7 minutes ago, Zeus said:

Thanks Clive,

Even the club shop supplied exhaust (which has all the right bends in all the right places) has a warped manifold flange on the downpipe. A straight edge reveals about a 1mm bannana bow. I guess the flanges get distorted when the two pipes are welded to it and no attempt is made to correct this afterwards. Perhaps I am picky but I don't think a gasket is likely to absorb that and the nuts/studs are surely not strong enough to straighten out the flange.

I have dressed it up and now I think it is pretty flat in all planes so I'll fit it without sealer on the gasket. The manifold is pretty good and I fitted new studs a while back.

fingers crossed.....

Zeus

isn't itgreat when things are not finished correctly. Yes, the studs would struggle, and I expect the gaskets to havehad a short life.

Hopefully your fettling will mean the gasket lasts well.

I have used these nuts (bigger size though) on cars, the extra length is reassuring and hopefully prevents corrosion on exposed threads.

https://www.ebay.co.uk/itm/371181189384?var=640327846785&hash=item566c1f7908:g:GLoAAOSwmUdUWNUg

 

[chrishawley]

On 23/02/2022 at 10:59, clive said:

manifold to downpipe gaskets blowing

I was bedevilled with exhaust manifold gasket failure on my Spitfire 1500 until I twigged that the missing piece was the bracket that stabilises the exhaust to one of the lower studs on the gearbox. Since I fiited one no further problems. If yours have gone awol then see

https://www.canleyclassics.com/?catalogue=triumph-spitfire-mkiv/1500&diagram=triumph-spitfire-mkiv/1500-exhaust-system-spitfire-mkiv-late

for what it should be like.