VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Engine rear oil leak

I restored my 1932 5-window coupe in 2010. The engine poured oil out the back. That was my number one priority in the restoration. My mechanic at the time (now my ex-mechanic) decided that replacing the side cover gasket, valve cover gasket and oil pan gasket would solve the problem. The engine leaks as badly today as it ever did. I'm now pulling the engine and have it completely rebuilt. All new gaskets and babbitts repoured, etc. Is there some way to put a rear main seal in these old stovebolt 194 c.i.d. engines? Is there an aftermarket seal? Can the engine be machined to accept a modern seal? What do I do to permanently fix this? What's the general consensus on replacing the babbitts with insert-bearings? All suggestions are appreciated.

If the rear main is correctly adjusted for clearence, all drain back things working, etc. it will not leak more than a drop after a long drive. Sometingm was done incorrectly or assembled wrong.
There is nothing wrong with the babbitted rods.....again if the rebabbitting was done correctly. Inserts are also babbited, necessary for a bearing surface. The original rods can be adjusted if they loosen-up and inserts have to be replaced if they loosen up.

Thanks Gene. As far as I know the engine has never been rebuilt - just had the gaskets replaced which did nothing to fix the oil leak. If it was ever rebuilt it was many miles ago.

OK, so the drain back passage in the rear main bearing cap may be plugged with sludge or the check ball stuck. Or the bearing is just too loose alowing more oil to pass through the bearing then the return can handle.
I thought the engine was rebuilt recently.

The rear main bearing leak probably had nothing to do with the gaskets mentioned above. The problem stems from either an excessively worn main bearing or the ball check valve in the main bearing cap stuck in the up position, thus not allowing the oil to return to the oil pan. If the engine is rebuilt correctly with the right clearances and etc. you should not have an oil leak other than a drop or two.

When you have the engine rebuilt I suggest that you have the machine shop remove the check valve ball from the rear main bearing cap.

Yes, a machine shop can machine the rear main for a seal if you want to go that route.

Thanks. Do you think it's worth putting in a rear main seal?

I have never heard of any one putting a rear seal in an engine if that type.Not sure if it can be done.

I have talked to one or two car dudes over the years that apparently have installed a rear main seal.

My 29 had a leak in the rear, come to find out that they check ball was stuck and the path full of crud. also when it was rebuilt they installed a felt type seal in the rear, this enhanced the leak by creating a wicking action :/

Removed the felt type seal, cleaned the check ball path and ensured free movement, and reinstalled rear main. no more leaking :) Know some guys have drilled out the Pin (you can see it in the photo) and then removed the check ball all together.

Ball Check Up Close

Rear main w/ Felt Seal Installed

Felt Seal Up Close

Felt Seal in Top Half

Thanks. I've about the check valve issue. It makes sense to me. I understand the check valve was designed to keep the oil from running out when parked on an incline. This car is never parked on an incline.

You will be better off removing the check ball to avoid any future issues.

I too had a leak in the rear and did all of the above except remove a shim or two. When I finally got out the plastic gauge, saw I was a few thousands too loose, removed some shims and problem solved.

Right! Having the correct clearance on the main bearings is critical.

Hi All and Olsarge
Beside the problems with the oil return passage in the rear main bearing cap plugged or restricted, the check ball stuck closed and/or the bearing to journal clearance excessive,the 1931 Chevy shop manual notes on page 25 about the clearance of the back of the oil deflector to the back of the block. This is set by the machining of the rear thrust surface on the center main bearing. The book says this should be under .032 inches. The way some machine shops perform their services now of days, this would be a good thing to check.