Rear main brg sealing question

[Ray31]

My friend has a recently rebuilt model A engine leaking oil from the rear main area. We are wondering if something is missing in that area. Does the rear main crankshaft brg use a seal itself or is it sealed by the oil pan seal only? A dealer selling replacement brearing caps indicates no seal in cap itself. What do you mechanics think; could you tell us a little about what is in there. Thanks, JD

[JFranklin]

Model A's all leak some from the rear main as there is no seal. the proper bearing clearance and a drain-back tube on the cap stop or return most of the oil, also the shims must be correct. if it doesn't leak a lot I would just enjoy driving it!

[Guest carlnut50]

If you forgot to install the paper gasket between the engine and the flywheel housing it will leak because the rear camshaft bore in the block is open to the outside.I did not omit this on my rebuild,but I know of others who did and ended up pulling the engine out again.

[pistoncollector]

Years ago I had a friend who had a similiar problem. We tried everything known to stop the oil leak and could not. Finally I pulled the rear main cap one evening and discovered that the rebuilder had cut the oil groove in the wrong direction. When cut properly, and looking down on the bearing surface from the rear of the engine, the grove should run for the right lower corner to the left upper corner. That way the rotation of the crankshaft pumps the oil back in the direction of the oil pan. If cut in the wrong direction the crankshaft pumps the oil towards the flywheel causing excessive oil leakage. I changed the new cap with an old one I had (after scraping the surfaces)and which had the grove cut in the right direction, and the leak went completely away. Afterwards I did some research on the subject and found a lot of information about cutting the oil groove in the right direction in my DYKES manuals.

Try this, it might be your problem.

Best......Paul