Oil Pressure

I've recently assembled a 72 455. Previously I didn't have an oil pressure gauge but thought I would add one this time go 'round. The engine runs nicely and strong however, I'm a little concerned about the oil pressure at idle.

When the car is cold, the oil pressure at idle is about 10 to 12 psi. When it's warmed up, the pressure drops to about 6 psi. . At 1000 rpm, the psi is up to about 12, at 2000 its 20 and at 5000 it's about 55 psi.

I should add that the car has a very healthy mechanical cam. I've been told to watch out for the chevy style lifters and that they may push up too high and expose the oil groove which could bleed off pressure. I've checked the lifter travel and I'm quite sure this is not the problem. The pump is a new melling high volume pump...not a high pressure unit and recently, I was advised to check the pump but went with a second brand new unit.

Any thoughts? I've been told by some that this is normal and by others that this a serious problem.