Jensen Monday Club

Exhaust Manifold Gaskets:

 

Tired of replacing blowing exhaust manifold gaskets? Then these "Percy Dead Soft" re-usable gaskets may the thing you're looking for.

The Monday club cars have tried all the usual alternatives, solid copper gaskets, etc, but had not a found a permanent solution until these were tried on 136-8494. They claim to be re-usable 5 times, and have so far been re-used 3 times, with no blowing or leaking. They have survived for about 18 months, with again no leaking or blowing. 136-8779 has just had a set fitted to stock cast manifolds. Take care to match the gasket to the manifold before fitting as they can be installed in different ways.

Click on: Manifold Gasket

James Barnes has done some research on the subject, and has come up with the following findings:

"Once again my exhaust gaskets have blown !
 
Felpro 1414 competition gaskets were tried, and without success. I had, in the mean time convinced myself that the reason I have been having these failures is because my exhaust manifold gasket face is not 100% flat.

This time it will be skimmed!

I had the flange face checked and the centre section was 0.025" lower than the outboard faces! So I purchased a new set of 1414's; then and only then did I spot the real problem.

 
Because the 1414 is a competition gasket the port openings have been opened up to allow for larger exhaust ports. If you use the standard head and a cast-iron exhaust manifold you will get a better gasket material with the 1414, but in places it will only be make a seal 1/16" wide!
 
No wonder that these gaskets fail on exhaust manifolds that haven't been skimmed and confirmed 100% true!"

The reason for the large port holes in the gaskets is because all the gaskets made for big blocks wedge engines are for the "Max Wedge" heads, which had huge ports for maximum flow. These ports have the same location as the 383-440 ports, so the gaskets will fit, but the ports are way to big to give a good seal. Unfortunately there doesn't seem to be gaskets made for the 383-440 sized ports.

Also, for maximum seal, the gasket face of the cylinder heads should be skimmed as casting imperfections in the gasket face of the head can cause hot spots which burn out the gasket.