I think you must had other problems?
The Felpro gasket works.

Warped manifolds, head surface bad?
Hardware not correct, manifold thicker mating surface than the header/exhaust manifold?
Did you check with a true straight edge?

I had checked 2 brand new Clifford side draft manifolds I got from them, first one was .060" warped, second was not much better, so instead of sending back for a third time, I just had the manifold resurfaced.

I never use any sealant on the Felpro gasket, it does not need it , as long as everything is clean, straight.

I am a big fan of Hylomar though.


I used the Felpro gasket when my 250 was supercharged, no leaks, I plan using Felpro when it will be turbocharged next.

I have even reused, used Felpro intake/exhaust gaskets with no problems.



MBHD

[quote=TJ's Chevy
I've tried several felpro metal gaskets and they never sealed. Never tried that "copper sealant" stuff I've heard of though. lol [/quote]

12 port SDS EFI