My Firebird has had oil pressure issues at high RPM pretty much since it was built, but so far it hasn't seemed to have hurt anything. Oil pressure cold is pretty insane off idle, I see about 55-60 at idle and above that it's spiked to 90+ at 2K RPM. Hot, it's 35-40 at idle, but I've never seen over 55PSI at high RPM ( 7K-8K ). I run 15W40 oil and have a 10296 Melling high volume pump. I'm running an F-body pan with the stock baffle. Recently I saw some troubling low numbers, but I am pretty sure it's due to E85 dilution. That happened previously, did an oil change and everything was good again. My car has a turbo, so the oil is definitely getting heated up more than normal. I run a little extra just to keep the pickup covered on launch, and I'm wondering if my crank is whipping the oil into a froth. Is there any way to determine that? Anyone else have issues like this? If so, how did you solve them?

 

I have essentially the same setup as you, fbody pan/pickup with turbo
Recently started tickling my oil pressure safety 40psi above 4000rpm.
Engine has never had good pressure, especially hot. Cold it would make 55psi idling, and stop at 65 even with revs. Hot it was just downhill. I figured just loose bearing clearances or spun cam bearing.

Ripped it apart and found pickup tube oring flat, like most high mileage trucks I see, but my engine is only 4 years old and probably 6000 miles.
Pickup tube was just under 1/4" from bottom of pan. Cut and welded bracket to increase clearance to 3/8"
Oil pump was M295 with +10psi installed spring. Oil pump was beat up, had same or worse wear than the 250k mile maliciously abused LC9 oil pump I also had in the shop.
Installed new M295 pump with +25psi spring(COPO), higher pickup clearance, and new Oring and my pressure cold is now 65psi idling and with cold revs 105psi. Hot idle gained 15psi, hot revs gained 15-20psi. Now around 60psi with high rpm.

 

Hmm, I might have to yank my engine this winter and redo my oil pump how you did. I never installed a higher pressure spring, just left the one it came with from Melling.

 

15w-40 oils are known to foam pretty bad. Since they are primarily formulated for low reving diesels they dont get much in the way of additives that cut foam down.

not saying this is your only possible issue, but it is one to make note of.

a crank scrapper, pan baffle, and better windage tray would help.

 

WAY too much oil pressure! 105lbs cold? Wow. I'll agree to disagree that you need that kind of oil pressure, but, IMHO, you're running about 35lbs too much. Too much windage, which costs power, and too much pump drag, which also costs power. I have a built LS7 with a Melling M365 pump. For the 60,000 miles I have put on the engine, I see 60lbs cold at idle, 25lbs hot idle. 50lbs hot at high rpm. I also have piston oil squirters, which reduce pressure some. But 100lbs, hot or cold, is ridiculously high oil pressure. I also think 15w-40 is the wrong oil to have in the motor. My .02......

 

I built my engine with clearances that warrant thicker oil. .0027 on the mains (.0030 on the thrust main) and .0022-.0023 on the rods. The diesel oil not having anti-foam additives is something to think about, though. I datalogged it and I see a drop starting around 5200 RPM. I don't think 105PSI cold revving is too much, the oil is cold and viscous, the pressure is going to be high. As he said, he has 60PSI hot at high RPM, that's perfectly fine. I would do a crank scraper/windage tray except none fit with a 4th Gen F-body pan. From the factory, the windage tray only goes about 2/3 of the way from the back of the block to the front. The pans are just too shallow up front. I may try a different oil and swap in a higher pressure spring.

 

I would be addressing the pickup tube to oil pan clearance. If you don't have 3/8" and you're using a HVOP you'll risk oil starvation at WOT. Had this issue with the 01 car and had about the same 1/4" clearance and it wasn't enough.

 

I run Lucas 20w50 oil in my setup and have had zero pressure issues at high RPM. I see 70+ psi hot oil pressure at WOT. I also run a shimmed stock pump. You want to pick an oil that can handle high temps that come along with boosted engines

 

With proper bearing clearance yes.

 

Improved Racing has everything you need to run a crank scraper, windage tray, and baffles in the F-body pan. They make quality oiling system parts.

Get rid of the diesel oil. Run a quality 40w meant for gasoline engines.

 

You said above that everything went back to normal after an oil change. How long after the oil change do you start seeing the reduced pressures again? It could be E85 diluting the oil like you said, or another oil degradation issue, if changing the oil fixes everything. It's crazy how much E85 can end up in the crankcase.

 

It took awhile, probably 1000 miles or so. I pulled the dipstick and it definitely had a fuel smell. It's the end of the season for me, so I'm going to pull the pan at some point this winter and check everything out. Does your low clearance windage tray/crank scraper work with the F-body pan?