I installed a 401 last year (someone else's rebuild). I started out with high oil pressure (http://www.bulltear.com/forums/viewt...292&highlight=), but took care of that problem.

But now, almost all of the sudden, I have very low pressure. Cold pressure is good (~50 psi), but when the engine warms up, pressure drops to around 10psi and I have lifter noise.

I've changed filters, checked the plunger and spring (they appear to function), and pulled the Bulltear oil relocation adapter to check out the oil pump.. pump looks good.. although I haven't taken clearance measurements. There was some minor wear on the relocation adapter.

I had the distributor out recently for a different reason, and noticed while the gears did not appear worn, the black oxide coating was a bit worn from the surface.

I'm wondering what the next step is. Replace the spring and plunger? Pull the distributor and check out the cam gear? Yank the oil pan and make sure I don't have bearing bits stuck to the pickup? Something else?