Is there any way to PERMAMENTLY eliminate rear main oil leaks?

It's probably about 8 yrs since I did a 100% rebuild on my 64 225. It most definitely had a rope seal. I think my rebuild gasket kit included a rope seal but I thought I'd update it with a "modern" lip seal. Also I was yrying to maximize power and a rope creates more drag.

I do remember the seal area on the crank had a directional knurling designed to direct oil toward tge seal. I'm pretty sure I smoothed that out some with some fine sandpaper shoe shine style. I don't think anyone has talked about that knurling.

I just checked the Dutra /6 book and he devotes 2 pages to rear main sealing.

A lip seal needs a smooth finish on the mating surface for any hope of sealing properly. I worked on gearbox design and stuff back in the 80's. If memory serves me correctly, we'd specify a finish of 8 micro inches on shafts in the seal area. That's a polish not a grind.

I remember servicing our equipment in power plants all around the country and every one seemed to have a drip pan under our older gearboxes. That was embarrassing to me and after investigating, tracked it down to oil weeping through between a key and it's keyway but that's another story. It was a design flaw started long before my time.

I may investigate a fix for the six but in the mean time, if I ever have my bottom end apart, I might go rope and lose a few oz-in of power.