1929 Pontiac oil leak

[tartop]

I am having the engine rebuilt in my 1929 Pontiac by the local machine shop. Everything has went pretty smoothly except they have an oil leak they are not for sure on how to fix. They have the engine running and probably have about 2 hours run time on it so far. There is an oil leak between the rear of the crank and the block. There originally is no gasket there. They say it is made to drain the oil from that area back down into the pan. We assume they always have leaked some because of the design but they are not comfortable letting it leave because of the size of the leak. Concerns with getting oil on the clutch etc. Does anyone have any suggestions on a fix?? Thank You for your help!

[GARY F]

does your service manual call for a seal.  maybe rope type.

[tartop]

I thought about the rope but my shop manual doesn't give any info. I do not have a service manual.

[Guest]

Did they insert the proper wooden seals on each side of the rear main cap?  If the rear main clearance is correct and the wood seals are in place the groove at the rear of the engine should carry the oil down to the drain hole and into the crankcase.  By the way EGGE has the wooden seals.

Are they running the engine on a stand?  If so that may be their problem because there is no suction through the crankcase and it builds up pressure.  When driving on the road the road draft tube alleviates this situation.  At an idle the air from the fan blowing into the oil filler tube is sufficient..

Did they use new pistons with all the rings above the wrist pin or reuse the originals with one ring at the bottom of the piston.  If so maybe they didn't notice that the bottom ring comes half out of the cylinder at the bottom of the stroke.  If a three piece oil ring is used here (rather than the original type) the first time the engine turns over you break the bottoms off all the pistons.

Edited January 11, 2017 by Guest (see edit history)

[Guest]

The seals in my overhaul kit from egge were a dense cork composite  9/32 square by 2 25/32 long.

Later Pontiacs used a wood piece similar to the one on our engines,  I used a pair of them on mine rather than the cork that came in the kit.  I don't see why the cork wouldn't work but I has a pair of the wood ones so I used them.  The previous machinist that installed my crank used the rope type seal in the space and silicone (it didn't work)  The only difference with the wood seal is that two sides are parallel and the other two have a slight bevel, making one side of the parallel sides 9/32 and the other 7/32.

[Guest]

For any other split head six rebuilders who happen to see this thread. 

I have rebuilt six of these engines, Three others and the one in my daily driver (three times in 58 years total mileage 500,000 miles).  I have always used  bearing cap seals 494663 as per my 1934 Master Parts List.  All packages bearing this number have been wood.  My last complete engine rebuild kit from EGGE (bought 3 years ago) included cork seals (a very dense cork compound).  On looking further today my "Sixth Edition" of my "Pontiac Six Parts Repair List 1930" (a small 6 x 9"  98 page book) lists "bearing cap cork 486072.

I find it Interesting that for 55 years I was always supplied with wood seal and assumed they were correct.  Now I get cork seals and assume they are an upgrade and discover that one of my 1930 books list cork.

I guess you can learn something every day even at advanced years.

 

[tartop]

Well the machine shop installed the wooden seals and it did not stop the leak. Of course I know it is next to impossible to diagnose an engine leak when you cannot see the engine but does anyone have any other ideas??