Brian at IMM worked hard to get me a small base circle roller cam that kept the lifters in correct relationship with the unbushed lifter bores so that oil would not bleed off. During assembly I ran the oil pump and spun the engine just to make sure. No oil leakage. Engine is now in the car running and oil pressure is very strong. Some factory blocks are very sloppy, like mine was, but Brian was still able to pull it off.