Oil Pressure - how much is too much?

[78DiMarco]

OK guys and gals, how much oil pressure is too much?
I rebuilt my twin turbo motor and originally it had about 60-70 pounds at WOT. After the rebuild with a new block I now have about 100 PSI at WOT and about 80 PSI at lower RPM's using standard 10/40 oil.
After the break-in I went to synthetic (Mobile 1 10/30) it dropped about 5 pounds at WOT and about 15 pounds a lower RPM's.
I've heard stories of bearing wash out because of to much oil pressure. Any of it true?
I know drag motor guys have told me that it's OK. But they run a motor for about 10 seconds. I run all day long. Any thoughts?
[ November 06, 2002, 11:28 AM: Message edited by: 78DiMarco ]

[Craig]

One of the biggest factors that eefect pressure is the oil temperature. I always ran in the 70-80 psi range. Then I put an oil thermostat that keeps the oil around 215 degrees. Oil pressure is 40 at idle and still goes up to about 70 at WFO. Rule of thumb is 11 psi per 1000 rpm.
Craig

[K3-River-Rat]

78DiMarco Do you happen to know what the rod & main bearing clearances were set at? the tighter the clearance the higher the oil pressure will be. Also what type of oil pump was installed when the rebuild was done? Do you have a high "pressure" pump rather than a high volume?? Were gonna need a little more info to help you wink

[DUCKY]

I have run motors with 100 psi several times. I have been told that it takes 125 to 150 to wash the bearings.
Your motor sounds just fine.
10 psi per 1000 rpm is the lowest acceptable
12-15 is just right

[78DiMarco]

K3, the rods are at .002 and the mains are at .0025, the oil pump is a high volume. My oil temp runs anywhere from 190 to 210 :) depending on how hot the air is and how long I have my foot in it :D :D .
I'm going to put an additional guage on it to validate what the guage on the dash is reading.

[Tinkerer]

It sounds to me like you have a high pressure pump not a high volume one. You are wasting Hp and causing excess wear to your distributor drive gear. Change the pump or the bypass valve in the pump that you have now.

[78DiMarco]

Tink, no it's a high VOLUME pump NOT a high pressure. wink

[waterslinger]

78D, I think you have a bad pump. The spring is to
stiff or the bleed off valve is not working good.
Moroso makes a blue printed pump works great.

[Tinkerer]

You are not doing your engine any good with that pump. You will tear up your distributor drive gear. 10 psi per 1000 rpm is all that you need for a performance boat engine. NO MORE NO LESS

[72Spectra]

An oil pump only puts out volume. Oil pressure is created by your clearances in your engine. Oil pressure is affected by the viscosity of the oil and the temp of the oil. When an oil pump is turning at high rpm it draws about 5hp off your engine. So make sure your engines warm before you lay the wood to it.

[78DiMarco]

72, I agree with you. I always make sure I have the oil warm before I put any RPM's to it. The new block and rotating gear was all machined to close tolerances like any good custom motor.
It's possible that the check valve is not releasing properly or there is something wrong with the pump as people have suggested. My engine builder still says that it is OK as do some of our fellow readers.
I need to put a secondary mechanical pressure guage on the block and see what it reads, then I will know for sure how much pressure I have.

[Tinkerer]

72spectra-- Yes the pump only puts out a fixed amount of oil per revolution but their is a high pressure version that comes with a high presure relief valve. With a properly clearanced engine it will produce over 90 PSI. That is way too much oil pressure for a high performance marine engine.

[72Spectra]

Tinker, what is the brand of this high pressure pump. Your right 90psi is to much. I saw once where a guy put to many washers in the relief spring setup and ripped the bottom of the oil filter right off. What a mess that was. The best advice I can give is to cut the oil filter open when you change your oil and inspect it. If something is coming apart you will know it.