if bearing clearances are different will cause this, also the pressure relief spring/valve in the pump maintains the pressure from the pump. also if one block has a drilled oil galley plug and one does not will do this as well...but checking with mech gauge as said before should be 1st..good luck Rob

you want the oil galley plug with the hole at the end of the path, I wanna say its the left side if you are looking at the front of the engine, check that to be sure because I am not sure, going off memory...