Thoughts on oil pressure vs flow?

[Marc Wulf]

This is the perfect opportunity for me to ask about my problem. I have good pressure at idle and cruising at Highway speeds, but at higher speeds and higher rpm i.e. 4500 over 100 mph the oil pressure drops. I'm using straight 30, but for this problem, I don't think that has anything to do with it. Any input would be appreciated.

[blykins]

If you're losing oil pressure with rpm, it's most likely that you're running out of oil in the pan.

Either you just don't have enough oil in the pan, or your pickup clearance is such that it's either being uncovered or too close to the pan to flow enough oil.

Could be some other causes too....a galley plug missing somewhere which causes an internal bleed, too much oil going to the top end, etc.

It's not uncommon to lose a few psi at the top end, but if you're just getting into the gas above cruise rpm and you're losing pressure, I would lean towards my previous thoughts.

[DanEC]

Originally Posted by Marc Wulf

This is the perfect opportunity for me to ask about my problem. I have good pressure at idle and cruising at Highway speeds, but at higher speeds and higher rpm i.e. 4500 over 100 mph the oil pressure drops. I'm using straight 30, but for this problem, I don't think that has anything to do with it. Any input would be appreciated.

There is another possibility for losing pressure at higher engine speed and that's an over-filled sump and the crankshaft frothing the oil (aeration). I experienced this in a Pontiac I once put too much oil in by accident and it was fine until I settled in on the highway and then it would start to lose pressure and the pressure would fluctuate.

[olddog]

Originally Posted by DanEC

There is another possibility for losing pressure at higher engine speed and that's an over-filled sump and the crankshaft frothing the oil (aeration). I experienced this in a Pontiac I once put too much oil in by accident and it was fine until I settled in on the highway and then it would start to lose pressure and the pressure would fluctuate.

Back in the 1970's all the gear heads I knew were using windage trays to keep the crankshaft from whipping up air in the oil, and it was claimed a small block Chevy would gain 25 hp at high rpm, by adding one. It takes Hp to spin air.

I have read on this site NOT to put a windage tray on an FE that has the solid lifter block, because the lifters only get oil from splash. Personally I don't understand that, because the splash should be oil coming out the sides of the main and rod bearings, not splashed up from the pan. So I would think the lifters would still get splashed. But then again, I do not know everything. I have learned that when people observe something, there is usually something to it, even if it is unrelated.

I also have noticed that a lot of FE owners are the ones saying they are using X-50W oil. There are some SB Windsor guys saying they use an X-50 W oil, too, but I also here 10-30W and 10-40W a lot more. I don't recall any FE guys saying they are running 10-30W oil. Now this is a come to think of it moment. I have NOT scientifically studied and accurately counted this.