Our local engine builder turned us on to these 1-piece rear main seals.
You can find them here about 3/4 of the way down this page.
https://www.roushcompetitionengines.com/performance-parts/We tried it Sunday, installed the crank in the block, torqued all the main caps. When we went to spin the crank it would hardly budge. We got out the torque gauge, it was taking right about 40 lb-ft to spin the crank. Sat there and scratched our heads, all of the main clearances looked perfect when measured. I started unbolting the caps, starting with the rear, and when got the rear cap bolts loose all of a sudden the crank freed right up. It was now taking less than 5 lb-ft to spin.
The crank is a Scat steel crank. The dimension of the crank at the seal matches every other crank we have in the shop, so I don't believe the crank is too big of diameter at that seal.
I asked an engine builder friend, he said yes he's used one (not on an FE engine), and it made the crank hard to turn so they threw it out and used a common rear main seal.
My question, has anybody on here used one and had luck doing so?? I'd like to run the seal because it seems like a better concept, but currently it's not working out so great.