I have a recuring rear main leak and can not seem to get it fixed. i just pulled the engine (400 block with eddy heads ) took it apart put new bearings in it a new ultra seal, ( the one that looks like a rope seal) billet alum. rear main seal retainer. all new gaskets. shined up the rear main seal area (68 383 steel crank, with the serrations ) put it back together . stuffed it back in the car , run it in for 20 plus mins like a new engine, (no leaks ) took it for a drive, about 20 miles. on the way back, the new seal started leaking again, real bad. pulled it in shop and shut it off, 10 inch oil puddle. I am at a complete loss. I am not a professional , but i have built 25 big block mopars over the years, and this is the first one ever to have this problem. This engine holds about 70 pounds of oil pressure at speed after warm up. drops down to 40 at idle. any thoughts, i know i got to pull it again, and tear it down , would like for this to be last time, want to drive this car (70 superbee, 4 speed ). any help would be appreciated.