Agreed. Just trying to show the difference between pressure and volume. As you said, its sometimes hard to type it the way that you want to explain it.

Yes, I am having an oil pressure problem in one motor. Somtimes pressure is normal, and then at times it drops down to as low as 10 psi (not after a hard run), I could just be idling at the dock. Shut the engine off and start it again, oil pressure may go back to normal (40psi at idle), or may me 10psi or something in between. Engine runs fine - I am pretty certain that the pressure relief valve in the oil pump has a problem. After this season, I am going to have to pull the engine an check everything out - was just wondering if it would be prudent to replace pump with a high volume style.

If the drop isn't related to temp, I'd look at the pressure sender/guage before anything else.

Hook a mechanical gauge and check it that way before you spend the time and money to pull the engine.

Sorry, I should have said that I have checked it with a mechanical gauge and the electric gauge operating together. Both read the same (high and low).

Just my 02 but make sure you check the pick up tube to the pump for leakage. This will - can cause problems. Also check pick up distance to the bottom of the pan.

For me with a stock 502 with proper bearing clearances a stock oil pump is the better choice. You really do not need 50psi at idle.

People seem to forget that a big oil pump relieving pressure just creates more heat in the oil.

As a general rule the system should maintain at least 10psi for every 1000 rpm. Preferably a minimum 30psi (warm) @ idle on solid roller and solid flat tappet camshafts to alleviate any valvetrain lubrication issues which can present themselves when running the higher valvespring pressures associated with the aforementioned applications.