If the bearings are still full of assembly lube they may hold pressure better than a running engine, the only way to know is to bar the engine over a couple of turns and check it then.
I just thought of something else, in later engines the top end gets oil through the cam bearings, and if they are installed wrong the bearings, lifters, and head don't get oil. I would pull the side cover and check the lifter gallery for oil.
