41 Cadillac Intake/Exhaust Gasket Creep

[Art Cutler]

My Series 62 coupe developed what sounded like a single cylinder exhaust gasket leak - only audible when accelerating.  It appears the leak was from the left exhaust passage into the intake manifold.  The attached photo shows the copper gasket pulled outboard - appears to be a ratcheting effect over many heating/cooling cycles.  I can't find and warping in the intake manifold using my best straight edge.  I did a couple of re-torques after the original installation and check manifold bolt torques a couple times every year.  I coated the copper gaskets on both sides with copper gasket spray prior to installation - maybe part of the problem.  Has anyone else run into this problem?  My plan is to reinstall with fiber gaskets from Olson's with the exhaust passages into the intake manifold blanked off.

[harry s]

Art, I have had that same leak. As a correction I used the Pyro Putty around that port. It has worked so far. If I ever have to fix again I would use the Olsen gasket with the block off feature.    Harry

[Bob Schuman]

Your exhaust gasket failure and leak seems not uncommon on the flatheads with the gaskets currently available. Check carefully the exhaust crossover port on the engine block, as it commonly gets eroded in the area toward the center of the engine. The manifold may show erosion also, but not as likely as on the block. If all surfaces are not flat and smooth, no gasket will seal properly for long. Any surface erosion can be repaired by PyroPutty 2400, available by an online search. It is hand applied, and after 24 hours curing time can be machined or hand filed to a smooth flat surface. I'm not a great machinist, but was able to hand file on mine easily. The Olson's gaskets with the crossover port blocked, is a good improvement, in my opinion, which will help minimize or eliminate hot restarting problems.

[Brad Ipsen CLC #737]

Had the exact same failure of new copper gaskets.  Fiber ones seem to be better but still failed but much longer life.  All surfaces had been machined.  Now use old NOS gaskets and no failures yet.

[Art Cutler]

Harry, Bob, and Brad,

Thanks for your insight.  Good to hear I'm not the only one having this problem and that there is a fix.  I'll used Pyro Putty 2400 on the block exhaust ports into the manifold (photo attached).  Amazing how much metal can get etched out over the years.  The manifold shows only a trace of corrosion.

Art

[Bob Hoffmann CLC#96]

Guys,
I probably have some NOS  steel & copper gaskets. Please contact me directly at bobscads@comcast.net.
Thanks, Bob