I got my motor running finally but I noticed after the coolant bleeding process (engine was running for a while), some oil had collected down at the bottom of the bellhousing and starter. It wasn't much but overnight it did leave a spot on the driveway, and it's frustrating because I should have absolutely no leaks (fresh motor, new gaskets and seals)

I thought it may have been running down from the back of the intake or oil pressure sender but I've felt around on those and they're dry. I even stuck my camera back there and took pics and it all looks dry. I'm stumped as to where the leak is coming from. Is it possible for a brand new rear main seal to leak?

 

Do you have a new crankshaft? If you turned the old one, you may have had a slight groove worn into the crankshaft.

 

did you check valve cover gaskets? slow leak at the VC will flow down the head to the starter. yes a rear main can leak, but I would look elsewhere before pulling the trans/clutch to check.

 

anything is possible but like ulakovic22 said i would look everywhere else possible before i yanked the tranny and clutch

 

You shouldn't need to yank the tranny to see. You only need to remove the inspection plate. Should be 4 screws/bolts.

 

What am I looking for once I take that off?

 

Oil.
A large, greasy, oily mess all over the back of the flywheel and slung all around the bellhousing.

 

Did you reuse your stock crank? The oil seal can and will wear the crank surface. It can put a slight groove wear the seal rode on the journal. Hard to believe but definately true. I have even seen UHMW plastic wear completely thru 12 ga. stainless steel.

 

did you lube the seal? some are meant to be installed dry, some are not....

also most leaks I have seen in that area on fresh engines are from the oil pan, did you silicone the corners? I always do the 4 corners and the front and rear curved part....

 

I had the same symptoms when I did my 383; turned out to be a leak at the pan gasket. I re-used the original gasket with my new Canton oil pan. When I installed it, I thoroughly cleaned it and RTV'd the corners, but it still leaked. I just recently had reason to drop the pan but this time I used a new gasket (from Canton)...no more leak

I had that leak for a couple of years, but there was still very little oil residue on the back side of the flywheel. So, like SS RRR says, if the rear seal is leaking you should see a lot of oil on the back of the flyweel.

 

I dunno if it's the oil pan. It has a fresh gasket, but one thing I know for sure is that the two metal "braces" that run along the left and right sides of the pan didn't get installed (I forgot all about them and left them at home when the motor was being built). They didn't seem THAT important but could that be causing a leak?

There doesn't seem to be any oil on the bottom of the pan, so if it's leaking, it's seeping right from the back of it at the top over to the bellhousing and stuff...

 

The pan rails are designed to ensure a proper seal. Without them you are squeezing the gasket unevenly and likely causing a leak. Look all around the pan, above the lip to see if there are any leaks.

 

It's possible one lifter bore is worn more than the others. Unless you want to measure them it's really hard to say why...

 

Most definitely. This reminds me of the stamped steel valve covers on MkIV big blocks. If you didn't use those tab plates, you'd get a leak for sure.

 

Some pics I took a few days ago:

This first shot is from the ground, look up along the passenger side at the bellhousing. Looks kind of like fresh oil there but it was hard to tell in person.



A couple of shots along the back of the intake. It appears to be totally dry.





Some shots looking at the back of the pan / bellhousing / inspection cover:







The bottom of the bellhousing and starter is where the fresh oil ended up collecting: