Oil Pressure High
Thread Starter
Instructor
Joined: Sep 2013
Posts: 118
Likes: 1
Oil Pressure High
Bought a 71 coupe (350/270) back in June of 2013 & oil pressure has read 70 psi from day one. I know that is not right, so do I just change the sending unit or do I concentrate on the gauge? When the motor is not running it drops to 0, so the gauge does not appear to be stuck. The guy I bought it from said the motor was recently re-built. Runs great & I am not having engine problems, but I want the gauge to tell me the truth.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 118
Likes: 1
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
The high volume pump won't get that done. Two things control the pressure, The bearing clearances and the max pressure valve. With that good of pressure, it should mean you have good bearing clearances. That's why I'd verify the pressure with an external mechanical gauge. Let's see if the number you're getting is correct first. May be much of nothing.
It's like a garden hose, you can run volume at just normal house pressure, Until you pinch the hose you don't get extra pressure. The better the pinch the higher the pressure. Same as the oil going through your bearing system.
The 3.8 and 4.1 Buick V6 oil pump kit comes with several springs to install in the pump to regulate max pressure so you can adjust the point where the over pressure bleeds off.
It's like a garden hose, you can run volume at just normal house pressure, Until you pinch the hose you don't get extra pressure. The better the pinch the higher the pressure. Same as the oil going through your bearing system.
The 3.8 and 4.1 Buick V6 oil pump kit comes with several springs to install in the pump to regulate max pressure so you can adjust the point where the over pressure bleeds off.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Either the sender unit is defective (causing a 'false' high reading) or the pump has been changed in some manner (aftermarket pump or changed pressure regulator spring). If you cross-check with another gauge that the pressure reading is correct, the only negative issues that elevated oil pressure will cause are:1) some small loss of fuel mileage, due to more power being required to generate that much oil pressure all of the time; 2) more engine heat created, due to that increase in power usage; and 3) harder working of the pump. None of those reasons would justify a 'special effort' being made to change/alter the pump immediately.
Wait till you need to drop the oil pan for some other reason....THEN work on the oil pressure issue.
Wait till you need to drop the oil pan for some other reason....THEN work on the oil pressure issue.
Last edited by 7T1vette; Mar 28, 2014 at 10:52 AM.
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Bought a 71 coupe (350/270) back in June of 2013 & oil pressure has read 70 psi from day one. I know that is not right, so do I just change the sending unit or do I concentrate on the gauge? When the motor is not running it drops to 0, so the gauge does not appear to be stuck. The guy I bought it from said the motor was recently re-built. Runs great & I am not having engine problems, but I want the gauge to tell me the truth.
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Pressure is determined by the bypass spring...but an HV pump can certainly cause the engine to be in near-continuous bypass regardless of the spring.
The Melling Select performance pumps typically come with both springs, and people seem to be reluctant to drive out the pin and replace the spring if the HP one is in there. It's quick and easy to do. The combination of HV and HP means the pump is in continuous bypass.
I'd agree that step one is testing using another gauge - but I suspect that it's simply a pump with an HP spring.
The Melling Select performance pumps typically come with both springs, and people seem to be reluctant to drive out the pin and replace the spring if the HP one is in there. It's quick and easy to do. The combination of HV and HP means the pump is in continuous bypass.
I'd agree that step one is testing using another gauge - but I suspect that it's simply a pump with an HP spring.
Last edited by billla; Mar 29, 2014 at 02:59 PM.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
A Corvette should have the high pressure spring. Standard spring maxes out around 55PSI or so. High pressure spring 70 PSI.
In this case I think someone installed a high volume pump. Will probably not hurt anything, but if it were my car, I'd drop the pan and install a standard pump (w/ high pressure spring) like the engine was designed for.
With 10W-30 oil and a fresh engine oil pressure at idle will be in the 30-35 PSI range. At higher revs it should go to 70 PSI.
In this case I think someone installed a high volume pump. Will probably not hurt anything, but if it were my car, I'd drop the pan and install a standard pump (w/ high pressure spring) like the engine was designed for.
With 10W-30 oil and a fresh engine oil pressure at idle will be in the 30-35 PSI range. At higher revs it should go to 70 PSI.
