oil pressure question

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furyus2

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My 440 when cold has 70 psi at 750 rpm. at 190* it drops to about 25 psi. I know the whole 10 psi per 1000 rpm, but my concern is the Difference in pressure from being cold to hot. Does this indicate worn bearings? These readings are with a high volume pump, and a bottle of STP.
I built this engine 20 years ago.
 
I bet if you use a straight 40wt it would not do that.
Without STP.
 
I bet if you use a straight 40wt it would not do that.
Without STP.
Ya know that’s exactly what I thought too. I was running 20w50 VR1 and at idle (800) when cold I had 65 psi and at temp (200*) I had 25psi. So I switched to a straight 40wt and now have 75psi cold and just under 25 at 200*. Go figure....
Now this is also California summer time temperatures if that makes a difference.
 
How high does it go when revved up hot ? 25psi is OK for idle speed
 
I use Rotella 15-40 my self oil PSI is 70-5 cold to about 20-5 at idle it's not a problem if I just breath on throttle it jumps up i have about 8,000 miles on it pretty hard to it my car is rear mount turbo set up.
 
How high does it go when revved up hot ? 25psi is OK for idle speed
I know 25 psi is ok for idle. My question is; Is the oil pressure drop from cold at 70 psi, to hot 25 psi going to be ok? It used to be about 10-15 psi higher a few years ago.
It goes up to about 80 when cold, and stays up there when I'm driving.
 
Any chance the relief valve is hanging, weak or possibly broken spring?
 
Yes, oil does get thinner with temperature.

That much of a drop is just wrong. It's not normal.

YEAH , BUT WHAT IS NORMAL FOR A 52 YR OLD CAR, THAT HAS EVERYTHING BETWEEN THE BUMPERS CHANGED/MODIFIEED/ OR REPLACED WITH SOMETHING BIGGER AND FASTER ?
 
My question is; Is the oil pressure drop from cold at 70 psi, to hot 25 psi going to be ok? It used to be about 10-15 psi higher a few years ago.

Every engine is a little different, so the best benchmark for comparison is your own engine. If you now have 10-15 less psi under the same conditions, then something has changed. You might send your oil out for analysis on the next change (Blackstone Laboratories | Oil Analysis - Learn What's Going On In Your Engine) to see if excessive bearing metals are present. Otherwise, it's pretty reasonable that after 20 years, your engine would benefit from a teardown and refresh. On the other hand, you have plenty of pressure at operating speeds, so another option is to just keep driving it and see what happens.
 
YEAH , BUT WHAT IS NORMAL FOR A 52 YR OLD CAR, THAT HAS EVERYTHING BETWEEN THE BUMPERS CHANGED/MODIFIEED/ OR REPLACED WITH SOMETHING BIGGER AND FASTER ?


I'm hip. But like the post above me pointed out...it's the change that is telling. Something changed.
 
I know 25 psi is ok for idle. My question is; Is the oil pressure drop from cold at 70 psi, to hot 25 psi going to be ok? It used to be about 10-15 psi higher a few years ago.
It goes up to about 80 when cold, and stays up there when I'm driving.

That could be normal, kind of depends on what the temp is and what your idle speed is and stuff like that. I've run a lot of engines on the dyno that held 70+ while cold but drop into the 20 range once the oil is hot.

If you really want to know what is going on stop asking questions on the internet and install a temp gauge in your oil pan. Then start taking notes. Write down the temp and the pressure and the engine speed for several different temps and speeds each time you drive the car. Once you have a good idea of how it is behaving then change the oil to a different viscosity and run the tests again. Do that three times and you'll be an expert. Then you can come back on the board and explain what is going on.
 
That could be normal, kind of depends on what the temp is and what your idle speed is and stuff like that. I've run a lot of engines on the dyno that held 70+ while cold but drop into the 20 range once the oil is hot.

If you really want to know what is going on stop asking questions on the internet and install a temp gauge in your oil pan. Then start taking notes. Write down the temp and the pressure and the engine speed for several different temps and speeds each time you drive the car. Once you have a good idea of how it is behaving then change the oil to a different viscosity and run the tests again. Do that three times and you'll be an expert. Then you can come back on the board and explain what is going on.
I was looking for possible directions to go. Wasn't really into becoming an oil expert. I would rather not have to add another gauge, weld bung in the oil pan, repeated oil changes, etc. I was just wondering if my situation means oil pump, or suck it up, and put in new bearings. Some of us are never going to be the engine builder you are( I mean that with deepest respect).
 
Wow. that was so useful. I hope when you ask a question, you get stupid answers, and get the finger.
Hey Man sorry if I hurt your feelings Man, apparently you like your engine Tight and Dry! Stroke On Dude.....:rofl:
 
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You didn't hurt my feelings. It was a useless, stupid remark, of no value. Same with your reply. still nothing.
 
So, a 50 psi drop, from cold to hot is fine?

A 50psi drop at idle speed.

If that was the only symptom it had, it wouldn’t bother me at all.

From what I’m interpreting you’re saying is........that there is almost no pressure loss between cold and hot from cruising rpm and up.
Only at very low engine speed is there a big drop in pressure between cold and hot operating temps.
 
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