Re: rear main leak
Benson,
It's better to use pressurized oil instead of air because oil is very visible.
You can go up to 50 psi if using a one-piece seal with the insert from Dan Price (dan4banger.com). The seal design is a radial lip and seals tighter with increased pressure. Try to rig up something like a hydraulic brake bleeder. If using the 2 piece design, I would not use more than 10 psi.
I also make Model A seals that are a similar design. They are one-piece only. Some years ago, one of these seals would leak after being driven fast on the freeway, but wouldn't leak if driven at normal speeds. When the pan was removed and the drain tube pressurized with oil to 50 psi to find the leak, there was no leak.
The engine used a Burlington crankshaft had been machined to provide the seal rubbing surface. The seal rubbing surface was verified to be concentric with the rear main bearing. Next, the crankshaft was drilled to get oil pressure from the mains to the connecting rods, and the engine was assembled and the rear main drain tube was pressure checked and verified that there were no leaks.
When the engine was completely taken apart, the seal rubbing surface was found to have .011 inch runout (tir). The seal instructions specify .001 inch tir.
When the crankshaft was drilled, stresses were relieved and the crankshaft was no longer straight. The crankshaft was straightened and the engine ran good with no leaks until the crankshaft broke at connecting rod journal 4.
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