I have rebuilt 253 v8 engine and the oil pressure drops at idling speed 500rev/min to 0 pick up to15 psi 600rev/min when put auto in gear drops away to 0 removed engine again and stripped it.
Put in new bearings and crank grind, refit engine. I have fitted new oil pump hv, and still doing the same thing. What do you think it could be? Thanks.