Phoenix64

iTrader: (3)

My 1998 formula used to hold 40psi anytime it was above 1200rpm.

So after a pair of 169mph runs on the autobahn(one in 5th one in 6th), the oil pressure dropped to 20psi at idle, and wouldn't hit 40 psi until over 3500rpm. It got better after cooling down, but it still is about 35psi where it used to be 40psi.

Also pressure goes up about 3-5psi when I let off, and down 3-5psi when I accelerate.

Does I really loosen up the enigne that much?

Why does the pressue go so low right after a run? is it possible the pump is cavatating?

Will the bottem end live through extended periods at 5500+ RPM?

PREDATOR-Z

could be a bearing issue.

BigRich954RR

iTrader: (1)

What oil is in it?

hirdlej

iTrader: (31)

Do an oil change, if it was shitty oil you could have broken it down. I'd start with the easy stuff first

DONAIMIAN

iTrader: (18)

I agree. My old motor had similar issues and the pressure would just keep dropping over time. Turns out the last cam bearing had walked and was about half way out the back of the block. These aluminum blocks expand a lot with temp and I'm guessing this was the reason for it. After my short block was assembled I found out that you could get the cam bearing pinned. I wish I would have done that, but now all I can do is keep this one as cool as possible.

SOMbitch

iTrader: (8)

Cut open your your filter and have a look when you change your oil. A UOA wouldn't hurt either. $25 here in the US.

If you were a little low on oil when you made those runs oil starvation is not out of the question. I run 6-6.5 quarts in mine for that very reason.....

Phoenix64

iTrader: (3)

UOA?

I use Mobil 1 synthetic, and fram filters, since thats all that is avalible here. 10W30

BYE RICE

iTrader: (2)

What? German Castrol isn't available in Germany?
Max speed runs by themselves don't cause this...Not if everthing else is working as designed...There are pleanty of stock LSx doing Silver State open road races with no problems...Now if something mechanical(like an oil pump) is getting marginal..Then a top speed pull might be the straw that broke the camel's back.
If you have a bearing issue, you WILL see it in your oil..Look for what resembles vaccum cleaner dirt in your oil when you drain it...Drain some into an empty Mobil one container..The bearing material will fall out of solution & accumulate in low spots of the oil bottle when you pour it back out.
My old motor had lower than normal oil pressure for about 3 days before the loud tapping removed any doubt that I needed a new engine.

SOMbitch

iTrader: (8)

UOA = used oil analyses. It wll tell you all the wear metals, silicon and other stuff about your oil so you can figure out what is going on with your motor. For instance a high copper count would indicate wear on the main bearings.

99WS7

iTrader: (13)

Id do the oil change first and the UOA too....the viscosity of the oil could have just broken down causing it to be thiner, thus less pressure.

allngn_c5

iTrader: (3)

Do you have an oil cooler ?? My new motor loses a couple pound of oil pressure when the oil gets above 215 degrees, but the normal pressure returns after if drops below 215. Only ran it hard enough to get that hot twice. Besides the oil cooler does a great job preventing the temps from getting that warm.

Phoenix64

iTrader: (3)

The issue that has me really curious is the loss of oil pressure under load, it has been as bad as 10psi. Hit the gas, and it drops, Then the moment you lift off the pressure goes back to 40 psi. Its the worst at about 1500rpm.

BBM98C5

iTrader: (2)

What you are describing sounds like it could be a blocked oil pump pickup tube screen.

BAMF

Could it be the gauge or the sending unit?

I had a oil pump crap out, I was letting it warm up one day and when I went out to get in it the oil press was at 10 psi, I shut the car off, towed it to town to have a new pump installed, no problems after that, I run Royal Purple 5W30 and always have 40+ psi, even after a pull to 150+mph or back to back 1/4 mile runs, one time it was down to just over 30 psi at a idle but that was after baggin the **** out of it on a +30 deg C day with older oil in it... I let it cool down and it was fine.

You might have a serious problem with your motor, I would pull it and check out the bearings if you don't want to have somting real bad happen while going down the road.