No truth to washing out bearings. Also - pressure does not indicate flow. Just the opposite. What you are doing is taking engine power and trying to compress a fluid. All that really means is the bypass valve in the pump is open a lot, and you're creating heat in the oil. The best case scenario is the 10psi/1k rpm if your clearances are per the factory manual. If they get wider, the pressure will drop - but that's what supposed to happen. If you run your clearances wider than factory specs, the larger volume pump should be used with the HP oil pump drive.