I ran a BM aluminum block for many years, and at least on mine you would start the run with 80 to 90 psi oil pressure and up the return road after the run it would hold 30 psi, from the block getting hot and bearing clearances getting loose I always assumed, and my main clearances usually came in at .0025 most of the time. Never had issues with cam bearings getting loose, but I was usually pretty picky about leaving the starting line at 150 degree water temp or a little less. It looked like the sleeves move around on an aluminum block as well. I used to leak test my engine regularly as part of maintenace, and the cylinders would get worse and then better sometimes, I never worried about it until they dropped below 20% leak.