Rear main oil pan seal
 

Have a new oil pan gasket set and it comes with two different seals for the rear main cap. One has to be squeezed in to work the other will fit but not as tight. Which should be used. I noticed the one I took off was the bigger one and the rear of the pan had cut into it pretty deep, thinking maybe the wrong one.
Any input appreciated.

Re: Rear main oil pan seal
 

I've used the over sized cork that I put a beveled edge on so it squeezes into place.

Re: Rear main oil pan seal
 

I use the thicker/wider one and it is a tight fit. Once pan is on and squeezed the cork even tighter it dont leek. ken

Re: Rear main oil pan seal
 

wrap it around a beer can with a rubber band the night before..or use super snot (weather strip adhesive) to hold it in place if you drink the beer..

Re: Rear main oil pan seal
 

There are two versions of the rear main cap; one is forged and the other is cast, which was introduced in April 1929. Ford was always looking to cut costs throughout the production of the A. Could it be that the cast version has a larger radius where it seals to the oil pan, needing the longer seal?

Re: Rear main oil pan seal
 

One of the caps referred to by Will N has a wider "groove" for the seal to fit into. I think, but do not truly recall, that the later caps has the wider groove. Us the seal that fits best, ie, goes in with just some resistance. No need to jam a wide one in a narrow groove. Lots easier if you pre form the seal as JShaft says. I put mine in a tuna can, keep a couiple in there all the time.

Re: Rear main oil pan seal
 

The cork rear seal is longer then needed and will need to be shortened a bit, go at it slow so you don't take too much off. Also put a bit of sealer at the ends.

Re: Rear main oil pan seal
 

Appreciate all the replies. Both seals were the same length and I used the one that is slightly thinner and slightly narrower. I trimmed the length to exactly 6 11/16" and it fits really nice, got this dimension from the leakless pan gasket PDF file. With the pan back on I can see that it just squeezes down where the other one that was slightly thicker was actually being cut into by the back edge of the pan. Much better fit and leak free. Thanks again for everyone's input.

Re: Rear main oil pan seal
 

You can also use an early small block chevy front timing cover seal which is neoprene.
Its the 1/4 thick one, trim to fit and a dab of silicone at edges.