My 1970 buick skylark has 77,000 miles. I am the second owner. It sat in a barn since 1988. I bought it and drove it home from st louis. 3 hour drive. It did not leak a drop of oil. I put approximately 1000 miles on it in the last couple of months. Never has leaked a drop. Currently have the motor out to install some high performance parts. Should I replace the rear main seal or leave it as is? Maybe it's a miracle that it doesn't leak. Car has great oil pressure.
IT IS A MIRACLE, I wouldn't touch it. These cars mostly use a rope style rear main, which almost always dripped at least a little. I would follow the if it ain't broke don't fix it theory. Although it's certainly hard to resist with the engine out!
It takes 3 hours, without a hoist to remove an engine from hood down to engine out. Been there & done it at least three times. Then another almost three hours to reinstall to hood down. Change the rear main while the engine is out. Rope seals do not normally last 77000 miles. It could start to leak the day after u reinstall the engine. 2 years ago we replaced the rear main with new style from T/A. We loosened the main bolts and lifted the crank which made it very easy to install the two piece seal + nails. Of course we retorqued the mains.
I'm on the fence. With 77K mi and now you're putting performance parts on it, it may not last. If you replace it make sure it a neoprene/polypropylene seal.
Your rear main seal is probably asbestos, and maybe why it isn't leaking. You can't buy asbestos seals any longer. I'd leave it alone. Just pop the oil pan and clean out any crap.
The "side seals" are installed along side the main seal seal into the block. They are held in place with a nail. they act as an additional sealing between the rear cap & block.
