I started this project 6 years ago and finally I get my 588 B1MC alum world block to the dyno and right after start up the rear main leaks. This isn't the first engine I have done and by some chance never have I had a rear main leak. I thought I read somewhere about these world alum blocks having issues sealing the rear main? Any thoughts or ideas.

Mike

Do you have a vacuum pump on it? Perhaps an 8 qt pan with 8 quarts in it? Was it filling the puke tank? Details please.