The Stovebolt Site Forums The Shop Area Engine Shop Exhaust gasket

On a 1955.1 with the standard 235 motor 3 speed trans, Does the exhaust pipe that mounts to the exhaust manifold seal up with a donut gasket or a two-hole flange (?) type gasket?

That's my project for the day. I have a flange type gasket hope that's all I need.

Thanks

According to the 1957 Chevy Master Parts Book it should be the flange type flat gasket, GM# 3692831. Sounds like you have what you need.

Thanks for the information

It depends on the shape of the manifold flange and the mating flange on the exhaust pipe. Some manifolds will work with either gasket, depending on the exhaust pipe they are mated with. If there's a 45 degree bevel at the manifold outlet, the donut gasket can be used- - - - -assuming there's a corresponding bevel on the exhaust pipe. The donut usually seals better than the flat gasket. If the flange is welded to the pipe, you'll need the flat gasket. Donut gasket systems use a sliding flange and a flared end of the exhaust pipe.
Jerry

yeah , mine has a doughnut.

I changed it out this morning and there was a donut in it. I installed the flange type in it and so far, it has sealed up. Only tested it for a few minutes as I couldn't run it long in garage. I will give it a good test this next week.
What about using both if a leak return comes back?

Jerry makes a good point that it depends on what your existing manifold/exhaust pipe setup is. I hope I didn't mislead you as I think since yours already had a donut seal that the flat gasket will likely not work properly for long.

My '51 3100 has a '54 passenger car engine which uses a donut seal. Knowing what I know now, I'd say you will need to replace that flat gasket to seal up your exhaust properly.

To further muddy the water in this little puddle, there's also a "half and half" donut with a flat side for a rigid exhaust pipe flange, and a bevel for the manifold. One of the three designs will solve just about any manifold/pipe sealing situation.
Jerry

If your leak comes back I don't suggest using both as the donut is intended to keep the flanges apart to compress the donut which would leave the flange (flat) gasket just floating in the space.

I gave the thought of using both, a little more thinking and agree that using both isn't a good plan, as WiCruiser mentioned. During the repair, I noticed that the bolts holding the pieces together were not using lock washers. I do recall just reaching over the fender and tightening them up from the top side and not inspecting any of the hardware last spring. It did seal up the leak only to return again. Perhaps just using some lock washers would have corrected the problem had I seen that there were no lock washers then and continued to use the donut that was in there already. I am just so concerned about breaking one of the studs on the manifold and opening up Pandoras box.
I did use lock washers upon the latest repair.
I guess only time will tell now.

Thanks as always to everyone. I can't tell you how many times I mention this site when talking to people about the truck and how helpful and lucky I am to have it available.

The time-honored setup that still works well is using brass nuts with a longer thread than a steel nut, and a dab of Never-Seez to keep the thread from seizing up due to exhaust heat. Those nuts can be snugged periodically as the gasket material compresses.
Jerry