I agree with Monte. Almost every time we have seen a rear main leak on a mopar the retainer was the offending piece.

x3 with Monte. Rarely have I had a lip seal fail (once out of probably 50 over the years?) , never had a rope seal fail.

If the block was line bored that is probably where the problem is. The seal retainer isn't putting enough pressure on the seal. How much to remove from the retainer to get the proper fit? Trial and error or pull the crank and measure. How loose is the timing chain?

If line honing the block, indeed has the crank too low in the registers, as some seem to be surmising, how is cutting the seal retainer going to do anything? Line honing has ZERO effect on the seal groove. If this was the problem, the seal groove would need to be cut deeper. Cutting the retainer on a line honed block, only results in the retainer "egg" shaping the seal, because the bottom seal register groove has NOT moved and neither has the retainer sealing platform. Lip seals are forgiving for a reason. They will conform to slight offsets of the shaft, hence the name "lip" seal. But if you squeeze it tight with a retainer and egg shape it, or put it to one side with retainer, it WILL leak. Some need to think more about what is actually happening here...........Line honing is only to get the bores round and remove taper. VERY little material is ever removed from the block, at least not by anyone who knows what they are doing. Loose timing chain? If you actually removed .002 from the block registers, that would be a LOT. How loose is .002 going to make a chain? Answer, none

If the surface is too course nothing is going last very long , it'll just keep chewing up whatever you put in it .

I believe you posted this elsewhere DVW and it sounded like a good idea to me. I believe you mean the retainer can be off from the center and not let the rear main actually be centered on the crank so you drill the bolt holes larger and do not use the side seals so the retainer will let the seal center on the crank and fill the sides with RTV sealer. I believe thats what you mean. Ron

that and look at the studs in the rear cap.

OP , what pan are you using ? I have seen where the studs on the rear cap actually keep the pan from completely seating against the block. I have had to machine the studs till they were flush with the top of the nuts to get the pan to fully seat.

If this is the case it will show marks on the pan.

The fact that it leaks when priming is saying your seal is either destroyed or you have a fairly good sized gap back there either between the retainer and the block, or the pan and the block, the only oil really getting to the seal is what goes past the bearing and crank clearance.

Or it's leaking from above , rear cam plug or the galley plugs , gravity is a funny thing ...

This is apparently a NEW or fairly new motor. It's leaked with various seals and probably same retainer. Rough or not, the knurling won't chew up a seal immediately, if at all. It also leaks while priming it. Highly unlikely the seal type, material or the knurl is the issue.

But was this the original retainer that came with
that engine... if it was I would think that it
centered on the crank... I hated changing retainers
due to this issue... from what he has said its got
serious issues.. the only 2 things that I see being
different is the crank and line bore.. as far as I
know they cut about .002 into the block for the bore
then match the caps.. nothing is done to the retainer

I have installed a bunch of main caps over the years when I worked in a machine shop, as well as line honing blocks. The caps come small, so first you line bore it, to get the size right and then hone it to round and straight. VERY little is taken from the block, if you do it right. That's why you cut the CAP on a line hone job. The retainer should never be cut, unless it sits on there crooked

Who knows if this is original retainer and who knows how it fits. Maybe it was cut. This is all stuff WE don't know.

Everyone is focused on the crank, the line hone, seal material, whatever. How about the OP sees if the retainer fits properly FIRST. Nothing else will matter if it doesn't fit.

This.

With the trans out, you should be able to see if it comes from above. If not that, make sure the retainer isn't sitting on top of the cap, or that the studs are holding the pan from sitting flush as said above.
The retainer thread bosses for the oil pan are in an area that could be hitting your cap.
In the case you have here, I don't think any suggestions are out of the question. Good luck!

Check and see if you put the main seal in the block one way and in the retainer the backwards. Never know.

when using a stud kit, i have always found the 12 point nuts to come in contact with the seal retainer. i machine a small clearance cut for both nuts. even the last billet seal retainer i installed on a buddy,s eng needed to be clearanced. also the windage tray will contact the studs possibly causing leaks.