I realized I have been keeping Facebook updated with my engine build but not classic Oldsmobile. So here's my Ford Y block rear main seal going in my 403.

 

Be very careful with the rtv on the ends of the seal. A guy on one of the other forums I visit had problems with a rear main seal leaking on a Big Block Chevy engine. He had replaced the seal twice in a year and still had a slight leak. I suggested he put the seal in completely dry other than some oil. It took care of his problem. I had him send both of the seals that he was having problems with and this is what I found:


Both seals were the same way. That rtv that had smeared into the seal was keeping it from working properly.

 

I built a SBC last year, and I did not offset the lips and ended up with a leak. I tried to use very little sealer on that as well. I used even less on this one. There is only a tiny smear on each end of the seal, away from the lips. I have also wondered about using 3m super weatherstrip adhesive or leaving them dry. I didn't want to use a rope seal, so we will see how it works.

 

I have never used anything on rear main seals. If you see how much of an interference fit they are you really dont need anything on the seal parting surface. They are mashed up against each other pretty good. When I did the 307 in my Wife's Riviera last year I used the Ford seal. She has about 3000 miles on it and it has not leaked a drop I think the original rope seal started leaking the day we drove the car home new