Fired the engine up, 50 psi oil pressure, no problems, all great..then on a test drive the pressure dropped to 10 psi, I limped it the block and a half at idle. I checked it with another gauge, sure enough 5-10 psi at idle. Beats the crap out of me, I've built a crapload of engines, this is the first one that had an oil pressure hiccup.
I'm using an aftermarket HEI distributor and am wondering if that might be part of the problem (the oil pump drive end). The oil pump is a Mellings hi-volume. I spun it with a drill before running it in order to prime the engine and it had 30 psi on the drill motor.