VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 31 Chev "Donut" Between Manifold & Exhaust Pipe

My "donut" gasket finally went bad after 12 years. Went looking for one and was told the correct size was either 2" or 1-7/8". O'Reillys Auto found a nos 2" triangular one that was too large. My local muffler shop put a flat one in as there was no angular opening in the manifold for it to fit into, but did have that ability to insert part of the exhaust pipe into the manifold opening with a flat gasket.
I think I remember putting a triangular one in years ago, but now I'm not sure what to use. Anyone have experience with this?
Thanks,
Peter

The flat gasket is what was original I believe. I did however use a donut on my 32 as it's a little more forgiving as far as alignment.

I believe the filling station has the correct exhaust donuts and I think they are 1 7/8” but not sure.

O'Reilly Auto Parts has the 3 sided "donut" Exhaust Pipe Flange Gasket # 31401 @ $1.99 and is 1-7/8" diameter in the center.
At the time I ended up putting a flat gasket in yesterday as it looked right. The manifold does not have an angular flange and the tail pipe has straight pipe to fit up into the manifold. I don't know if O'Reilly has a flat one. The Filling Station offers a 3 sided one.

In any event, I would surmise that a flat exhaust gasket would be the proper one for a 31 Chevy.

I just felt with this the other day on my ”˜32. The new exhaust system came with a flat washer but once everything was install there was a leak between the manifold and the down pipe. I found that it was because the way the exhaust mounted under the car it did not allow for the down pipe to meet up to the manifold perfectly straight. I went to NAPA and looked though their exhaust gaskets. I was able to match the inside diameter on a thicker donut style gasket. This solved my problem as it was able to take up a little extra space between the manifold and the exhaust. Once installed you can’t tell that it is a different style gasket if you are going for the factory original look.

The catalog dated 1939 shows this to be the 29-33 exhaust gasket packing. Looks like they were making a donut by stapling three layers of material together.

Dave

The original exhaust pipe gasket was indeed flat. However the donut replacements seal much better than the flat ones.

I did a little further investigation and saw that the down pipe has a flange, like a big washer, about 1/2" or so down on the pipe, allowing a flat gasket with enough room for the down pipe to fit up into the manifold.


The bottom line is to use whatever seals your exhaust system. I have a flat one installed.

Now I know what was originally intended, and what works. Thanks for all the input and picture.



On a side question, does anyone know where the older copper clad manifold gaskets can be purchased?

Thanks again !

I bought copper clad gaskets for my 31 Buick at Olsen's Gaskets, Port Orchard, WA 360-871-1207. They are very helpful but I don't know if they have copper for Chevrolet.

Dave

I think you got your answer but I noticed the catalog also shows a flat gasket in the group below. I wonder if you were suppose to use both or there were two types?

Dimensions of the 372029 are od 2 1/2, id 2 1/16, 1/4 thick. Also I was incorrect it is four layers of material not 3.

Dave

I purchased a copper manifold gasket set from Olsen's Gaskets today. I'm pleased as they had the flat gasket that goes between the manifold and the down pipe.

Thanks for providing your information, Dave.

Ebay has flange gaskets/manifold gaskets. I just bought one for my 35 Standard. Original part number reference and measurements. They had other gaskets flat and angled on both sides. Fel Pro gaskets. Around $10 plus or minus a buck. free shipping.

Olson's Gaskets are great to work with. They go out of their way to assist. And the owner has a 1931 Chevy, too !

Yes they are great. They even offered to make something special that they did not offer. A very good experience.

Dave