nsm

I've been replacing the donut gasket constantly (every 1-2 months) on my 1966 200 cu.inch. I don't know how the original cars were then, but I really don't think that was like that. I need to check my timing though, but I wouldn't think it would mess my exhuast up. How often does a donut gasket usually suppose to last?

Soaring

About 40 years. Yeah, you just didn't get the donut in right in the first place.

GypsyR

Likely you're looking at the wrong thing. The engine vibrates when running and wiggles under acceleration/deceleration. Moves around quite a bit. The rubber motor and transmission mounts deal with not transmittting all this to the rest of the car. BUT...you exhaust pipe is bolted tightly to your manifold. With all the rest of the wiggling goin on, something must give here. On almost all cars the entire exhaust is free to move around and it needs to be. Some folks make the mistake of welding or bolting exhaust or muffler brackets to the car instead using correct rubber hangers in between. Check it out. You should be able to shakes you entire exhaust system by hand all the way from about two ffet from the manifold all the way to the end. If not, then what will give is usually the donut. I've learned this the hard way. The same thing often happens with custom dual exhaust and headers. People blame the header flange gaskets and never think to look at the tailpipes.

85lebaront2

You are probably missing or have a broken bracket. From what I remember, the inline 6 had a small braket bolted to the side of the block that was clamped to the exhaust pipe. This made the exhaust system move with the engine so the donut gasket didn't get destroyed. If you look at the engine and you should see a bolt hole right in line with the exhaust pipe, just above the oil pan rail. This is where the bracket goes. It is only a couple of inches across, one end flat, the other curved to the exhaust pipe. It was held to the pipe with a clamp.

Scott H.

Good catch.
The next hanger wasn't until way back at the muffler, so that bracket is muey importaunt-A.
Also applying even tightening in steps to both nuts on the flange, and not over tightening is very important. The flange should be flat. If not, you need to make it that way. Maybe somewhere in the previous ownership it was over tightened and bent. If so, a good muffler shop can help you out. If left undisturbed, the donut gasket should last the life of the engine.

One last thing. Anti-sieze on exhaust bolts can be your very best friend.

Good luck,