[steve25]

I would ask your engine builder exactly what clearances he saw when he assembled the motor and if the crank was cut and or the block was aline honed if he had a hand if that which produced the clearances you now have.

The one time in a 400 motor with 10w40 oil that I saw less then 18 to 20 psi at idle with a 60 lb pump was when my pump check ball was held open by a sliver of gasket material and we are talking a 800 rpm idle speed.

[mgarblik]

So based on your recent post, I agree, your pressure readings are "real". Your not in the danger zone, IMO. If the pressure jumps right up as you describe, I don't think you have anything to worry about. So why is the hot oil pressure somewhat low? Nothing that doesn't require taking the engine back apart to know for sure unfortunately. As you know, oil pressure results from the resistance to flow. So where is the engine most likely pissing out oil at hot idle? It's a long list. 1. oil pump check ball to seat leakage, pretty common
2. aftermarket connecting rods with giant side clearance
3. aftermarket crankshafts with over-wide crankpins, huge fillet radius, used with narrow bearings. (Eagle, very common)
4. undersize lifter OD, worn lifter bores
5. unrestricted oil flow through lifters, especially hydraulic rollers
6. main bearing clearance over .003 on 400, .0035 on 455
7. I may have missed some others.

I would end by saying when I worked at the Pontiac dealer as a mechanic, we had many Buick V-6 powered cars come in during the summer with the oil light flickering or on steady at idle. Especially with the AC on in Drive. 500-550 RPM. The oil light had a sending unit that would close the circuit at 5 PSI. GM issued a replacement sending unit that closed the switch at 3 PSI. That "FIXED" the problem. So I wouldn't fret too much over it.