My exhaust on my f100 is completely stock and its a 72 my question is would a clogged muffler cause the doughnut gasket to come apart like a slinky when the pipe is pulled from the bottom of the manifold I also think my intake/exhaust manifold gasket is probably needing to be replaced and possibly the one under the steel plate I used to block off the top of the exhaust manifold. When I first installed my 4 barrel it was running way way rich as a result of having been set up for something else by the previous owners, although as of right now my spark plugs look great so I need to know if fouling out the muffler would cause it to blow out all the gaskets the thing still runs but before I go and drop several hundred dollars I'd like some opinions.

 

Usually a blockage in the exhaust system, like a plugged cat or muffler, can blow the donut out.

 

Ya I cut the muffler off after it didn't like turning over and it appears I took the 39yr old muffler and put a end to it while tuning my 4 barrel. Now I am just waiting until I come up with money to do the exhaust. It'll start though and runs but being that the intake/exhaust gasket which is about 3 weeks old needs to be replaced I am just going to do the entire exhaust.