Ok I’ve tried two of those Mancini billet seals on my last two biulds. Both came in as leakers. One Still leaks but the other is sealed fine. My guy that does my machine works has a 440 builds that has been through several seals with the stock retainer and they still leak. These things are hit or miss seams like on B.B. Mopar. My question is will the factory rope seal work better and can you still get them? I remember always having oil leaks back in the day and it was just something you lived with.

After years of never having a leak, I was talked into a billet retainer, and new style seal. Leaked horribly from the get go. Took it out, installed a FelPro Viton seal, and the stock retainer, and the leak was gone.

What he said...I have also had good luck with the Superformance rear main seals..

Although I'm not certain what brand Superformance uses, they are probably the same Viton rear seal that the Fel-Pro is... they are all sourced from major "seal" manufacturers. Changing the retainer is most helpful.... regardless of the seal source.

I'm a former long-time aftermarket engineer from Fel-Pro.

all of my "rear main/pan" leaks were from something else. it's time consuming but be patient and look for other sources of the leak before tearing into the seal.

THIS x10!!!!!

https://board.moparts.org/ubbthreads/ubbthreads.php/ubb/showflat/Number/2815954/Searchpage/1/Main/232394/Words/%2BRear+%2Bmain/Search/true/billet-rear-main-seal-retainer.html#Post2815954

but I'm not a long time gasket engineer
I buy those seals by the dozens so I don't run out on the weekend or at night, no leaks in a longtime on both knurled or smooth cranks

I got three of them Billet retainer. Two of them in use. work well for me. One of them has got O-ring on the side it is junk don't like it at all. I always use them FelPro Viton seals..

i'm not an engine builder, but from years of reading about rear main leaks on big blocks, having the retainer bolt holes drilled a touch oversize may allow the retainer to seat the seal to the crank better without the bolts "pulling" the retainer to one side or the other, causing a leak ?
or am i missing something ?
i'm looking closely at this because my charger and panel truck are both big block powered.

I followed Monti's direction on installing that rear main seal. I used the billet seal retainer and Superformance seal clocked at 12 oclock and 6 oclock on the parting lines. no leaks the first 2 seasons, then the leak started and hasn't stopped. I just live with it.