Damn oil leak, Rear main??

340Duster247 said

Hey guys, I've had this little small block in and out many times with various combos and rebuilds and along the way I've never had an oil leak that's acted like this one so maybe you could help me out.
This is bar far the worst oil leak I've had, shut off the engine and got the dreaded drops coming from the back upper of the pan. "f**k I guess the engine had to come out" but before I pulled the engine I figured I would investigate. Seeing how this new engine/combo just went in at the start of summer I'm not really to motivated to yank it.
Got under the car and cleaned up everything removing any oil mess since this leak happens to get onto the flex plate and spatter everywhere.
With it all clean, I start the car and wait and look. Nothing. Dry. Zero leaks. Let the car idle and get up to temp. After 30 mins of run time I rev the engine a couple times. Under the car still nothing. Dry.
I shut the engine down, get under the car and it instantly starts coming out at a pretty good pace.
Hmmmm, rear main seal???
Anyone had a similar leak.
I think I have an idea what's going on , but want to get the wisdom from you guys first. Lol
Added a photo of the leak and new combo for ya guys too.

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I have lately been wondeing about those rear main seals.

There is the earlier rope seal and the angled knurling on the crank seal area. I can see how this works with the engine running winding the oil back into the engine with the knurling. With the engine sitting off, can the oil seep back through the knurling?

Then on a rebuild or newer lip seal rear main seal. The new lip seal sitting on the knurling, with it running pushes the oil back into the engine.

With the engine stopped the new lip seal would be bridging the knurling peaks and allowing oil to run back out throgh the knurling valleys ??

So my question is with the lip seal style rear main seal, would it be a good idea to polish down the knurling smooth so the rear main lip seal has a smooth surface for the lip to seal against.

Just like the smooth surface seal up on the front harmonic balancer and timing cover.

Also wondering if the aftermarket cranks and stroker cranks have eliminated the knurling altogether ???

Maybe even the stock reman cranks have the knurling removed as part if their reman process ??

Granted you want a good vented crank case and PCV setup to eliminate any positive crank case pressure pushing the oil out.

Any thoughts or opinions on this ???