I have 0 oil pressure at idle

Question:

I have a 1947 Ford pickup with the original V-8 engine that I had overhauled. They put in pistons, bearings and everything else that it needed plus adjustable lifters.

The problem I have is the oil pressure. When the engine is cold the oil pressure is 80 psi.

But when the engine is warm it’s 0 at idle, and the pressure comes up to 10-15 psi when driving.

I have installed both electric and mechanical oil pressure gauges and have also installed new springs in the relief valves in the oil pump and the one under the intake manifold without success.

The old Ford collectors I know tell me not to worry about it, that the engine has floating bearings and doesn’t need much oil pressure. What do you think about my situation?

Answer:

I agree that the engine does not need a lot of oil pressure, particularly at idle, but it definitely does need more than no pressure whatsoever.

Good oil pressure when the engine and oil are cold in conjunction with very poor pressure when the engine and oil are hot usually indicates that bearing clearances inside the engine are excessive.

Another cause (or possibly one of several contributing factors) of the pressure differential is excessive oil temperature. Oil gets increasingly thin as its temperature rises and oil pressure decreases as the oil gets thinner.

So, an easy first move is to install an oil temperature gauge to determine whether the oil is excessively hot. Assuming it’s not, I’d try installing a new oil pump as my next move.

If a new pump doesn’t help then you should measure rod, main, and cam bearing clearances.