Chevy Big Block Oil Leak

[pip69Chevelle]

I am new to the site and own a reasonably restored 69 Chevelle SS 396 Mark IV (not Pro Touring....yet). Body and interior very good to excellent. Powertrain also quite good as leak down and compression all good, no smoke, uses no oil and performs quite good, tranny just fine with Hurst shifter and linkage. I had clutch and flywheel replaced and have a MagnaFlow stainless exhaust system done from headers back. Not sure what or when engine rebuild happened but it is dressed like a L78 with Winters intake and Holley 750 double pumper. Not an L78 though. In any case I had all work performed by a highly reputable classic muscle car shop here in SoCal and also had them attempt to resolve a small but annoying leak from what appeared rear main. Dye was used and black light. The leak persisted so they redid the project a second time and leak persisted maybe a bit worse. It so frustrated them they did it a third time and now leak is so terrible it really cannot be driven. They are going to to replace all of the gaskets again for fourth time and use silicone. Maybe pressure form main cap due to poor tolerances? Needs a line bore as first one was bad? These guys are good but are stymied. Any ideas how to resolve?

[reschke18]

Not sure what they have/haven't done, but my big block doesn't leak at all. I have the standard 2 piece fel pro rear main seal, and a one piece oil pan gasket. Hopefully they know which way to install the lip of the seal to use the pressure to help seal it. I put a little Permatex #2 on the edges between the seals and I also like to use a little Permatex 300 or #2 under the rear main cap and in the corners to stop any seepage. Then I put Permatex ultra black in all corners of the pan both on the block side and on the pan side, even though it is a molded seal. The quality of your oil pan will play a big role in the sealing ability too. Check the lifter bore plugs for leaks, and check your oil pressure port above the oil filter to make sure that is not it. May want to verify the crank is not scored, allowing oil past even the best of seals. Good luck!!