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Exhaust manifold recurrent leak

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Shortly after I acquired my TR7 Sprint the exhaust manifold started blowing. Fair enough, these things happen.

On investigation a couple of threads in the head had stripped, so I helicoiled the lot, fitted studs, checked the manifold was flat (it wasn't) and refitted with a new gasket.

Spent Sunday at Debden Sprint hooning round and on the way home, exhaust started blowing again at the manifold. Obviously I'd like to try and prevent this happening on a regular basis.

The TR7 Sprint has an alloy head and the tubular exhaust is stainless steel. Original Dolly Sprints had cast manifolds with no gasket fitted. There are only 5 studs. The tubular exhaust flange looks a bit thin to me.

So, why did the factory not fit a gasket and should I try the same?

I was thinking of trying a double gasket, would that work?

Is it worth trying a sealant, what would work at the high temperatures?

I noticed recently working on my son's MX5 that the exhaust manifold gasket (alloy head/steel exhaust) utilised a multi-layer steel gasket. What's the reason for that?

I used to have a Spitfire 1500 that would regularly blow the manifold to exhaust flange gasket. This had a poor design of 3 studs and the exhaust flange was never flat. I fixed this by filing the flange flat and using 'K' nuts. Perhaps the 'K' nuts would help in this case too.


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You can get sheets of the metalised exhaust gasket on EBay and make your own. I’ve used them with great success on various engines where gaskets are unavailable or poor quality fibrous rubbish.

The sheet is metalised both sides with softer sealing layer between them. 

With strong hands and a stout pair if scissors you can cut it, the big holes can be done with a stanley knife or hole saw depending on the required shape. When drilling for bolt/stud holes it’s best to do it between two pieces of wood to avoid ragged edges.

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