VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 1936 chevy 209 ci burning exhaust donuts

Gm .. got a 1936 chevy standard with a 209 ci .. im running split manifold with straight pipes.. i keep burning out my exhaust doughnut that sits between the pipe and the manifold ( closer to firewall) . I burn them out after about two cruises had it checked and replaced by a muffler shop but still continues to happen .. im guessing a small leak would cause this but thier doesnt seem to be any leaks once replaced with a new doughnut.has anyone else ever experienced this and what else should i check ..any suggestions? Thanks

There are two things that will cause exhaust donuts to leak: 1. Lack of compression on the entire donut. If there is any even small leakage between the manifold and exhaust pipe the heat and gas flow will eat out the material. 2. If the exhaust pipe can move, wiggle or wobble the same thing will happen. If there is a good complete tight seal there should not be a problem.

Chip is right on the mark, any leak or movement will cause it to quickly fail. One more question. Are both pipes the same? I have seen some pipes have an extra sleeve in the center that gives support and containment of the actual gasket. It protrudes up through the doughnut into the base of the exhaust manifold and has a flared out shoulder where the doughnut sits. Looks similar to a double flare used on brake lines.

If the pipes do not have that it might be something to build and try.

No it does not have that extra sleeve.. we replaced doughnut with a metal one .. no idea how those doughnuts preform .. going to see of that extra sleeve will fix problem if this metal doughnut doesnt work out .. thanks for the help from everyone who responded