Exhaust leak at the h-pipe/header flange


Founding Member
Sep 26, 1999
Pleasant Hill, CA
I have a 97 Saleen S-351 that came with off-road exhaust. I am having to put the stock h-pipe on for a while, and I am having some major problems with the passenger header flange.

I know Mustangs, especially SN95s, have exhaust leak issues at the passenger header flange. I have done anything and everything to resolve the exhaust leak, but it doesn't go away. The leak is REALLY bad, and renders the car undriveable. Any ideas? Is there anything I can do to ensure a good seat between the header and h-pipe flange?
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Why was this moved to a 4.6 forum, when the car/chassis/motor are all based on the 94-95 5.0?!? The h-pipe/header problem is primarily found on 94-95 mustangs, as the header flange was changed out to a flat gasket after '96.
Because it is a 97 someone figures it should be 4.6. If the swap is temporary maybe use some high temp RTV to get a good seal? I did that with my 96 with the flat flange. I assume your flange is the bell type?
If you don't have access to a smoke machine, a little seafoam in a manifold vac line can help you find the leak.
Is it leaking where the EGR tube connects or the tube itself cracked??

With those bolts you have plenty of lenght. double up on the gasket, thats how I run mine as I was getting some noise too...double Fel-Pro 1415 I believe.