oil pressure

famous bob said
Andy; wouldn't the oil pressure relief valve opening sooner drop the oil pressure straight across the rpm range , because it would openquicker?

While a relief valve with a lower pressure setpoint would open sooner, it would not have any effect on oil pressure BELOW the relief pressure setpoint. Raising the setpoint reduces the blow-off flow to the sump, which in turn increases the flow to the galleries. Higher oil flow has more pressure loss from fluid friction, which means the pressure "seen" at the pump is higher.

As explained earlier, the oil pressure relief valve only limits the maximum oil pressure and oil pressure is a reflection of pressure losses in the oil system in response to the oil flow generated by the oil pump. You were able to raise your hot oil pressure at idle by shimming the relief valve spring because your high volume oil pump is putting out so much flow at idle that it is causing the relief valve to continuously blow off excess pressure.

famous bob said
I might have mis-stated the restricted oil to the top end. I have full time oiling to the top, and had to restrict it the best I could w/o pulling the heads.
I made the mistake of drilling the lifter galley deal like a guy on here said he did all his engines, it put way too much oil up there, ( big mistake guys, don't do that ) , so I restricted the drilled holes the best I could /under the intake. Then tied the tubes going up , together w/ 1/16'' line, and machined a couple of restrictors to go around the bolts that feed the rockers, therefor closing the opening around the bolts down.
I suspect I still may have a little too much to the top, AND , can drill and install jet type restrictors in the deck surface, if I ever have to pull the heads, which I really don't want to do if I don't have to.

Since andyf found that he was not able to measure a significant variation in pressure at various points in his oil systems, the oil pressure losses in the galleries is normally small from the oil pump to the oil pressure gauge port. In your case, because the oil pump develops so much flow, the oil pressure at the pump is always at the relief valve's setpoint or greater.

Somewhere in your system, the oil flow at one or more branches from the oil galleries is relatively large compared with the flow supplied by the oil pump to the engine. The normal big block pressure gauge location is pretty much at the far end of the oil system and most of the pressure losses occur upstream of the gauge.

If I'm reading the oil system diagram correctly, this is the order that the following branches receive oil flow between the pump and the pressure gauge:

crankshaft + camshaft bearing #1
exhaust valve lifter #2
intake valve lifter #2
crankshaft + camshaft bearing #2
intake valve lifter #4
exhaust valve lifter #4
crankshaft + camshaft bearing #3
exhaust valve lifter #6
intake valve lifter #6
crankshaft + camshaft bearing #4 + L&R rocker shafts
intake valve lifter #8
exhaust valve lifter #8
crankshaft + camshaft bearing #5
left main oil gallery (lifters for cylinders 7,5,3,1)

Mattax said
Thanks Andy! That would suggest very little loss of flow from the pump through the oil galleries.

I think you mean there is very little loss of pressure because the oil galleries carry the entire useful flow output of the pump.