oil pressure too high?
Thread Starter
Instructor
Joined: May 2012
Posts: 119
Likes: 5
oil pressure too high?
1976 stock L48 4spd
when driving and engine at about 2000-2500rpm (~55mph) the oil pressure is about 70-75psi. goes back to about 50psi at idle.
Is this normal or high?
Thanks,
Mike
when driving and engine at about 2000-2500rpm (~55mph) the oil pressure is about 70-75psi. goes back to about 50psi at idle.
Is this normal or high?
Thanks,
Mike
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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Has anyone been into the engine? Sure looks like a HV pump. If not..I'd test with a mechanical gauge.
If it's accurate I'd change to lower vis oil. I don't mind high pressure..but you don't want it pegged/on the bypass all the time. It should only get super high when at WOT with some RPM.
JIM
If it's accurate I'd change to lower vis oil. I don't mind high pressure..but you don't want it pegged/on the bypass all the time. It should only get super high when at WOT with some RPM.
JIM
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Someone has installed a different oil pump or maybe installed a higher pressure relief spring in the stock pump. The higher oil pressure isn't really a problem for you. But, it will work the pump harder and use a bit more fuel. Otherwise, just ignore it.
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Racer
Joined: Jun 2013
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From: NJ
I would put a mechanical gauge on it to double check the pressures. 
I wouldn't assume that the oil pressure is to high without double checking with a good mechanical gauge first.
Also, the sending unit could be wrong or defective if someone replaced it with the wrong one. Or your oil pressure gauge could be off.
I wouldn't assume that the oil pressure is to high without double checking with a good mechanical gauge first.Also, the sending unit could be wrong or defective if someone replaced it with the wrong one. Or your oil pressure gauge could be off.
Pro
Joined: Dec 2011
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From: Austin, TX
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Mine is near 80psi as soon as the revs get above idle. Actually it is probably 70-75psi but if I give it a shot of gas it hits 80psi. This is on a hot day too.
I built engine for the correct oil clearance and I am running the Melling Z28 pump I have used on many engines. The engine has 20k on it now and the high pressure doesn't seem to seem to be causing any problems. I am running 20W50 Brad Penn semi-synthetic oil.
I am a little concerned now after reading above that it could bypass the filter but the engine runs perfect.
I built engine for the correct oil clearance and I am running the Melling Z28 pump I have used on many engines. The engine has 20k on it now and the high pressure doesn't seem to seem to be causing any problems. I am running 20W50 Brad Penn semi-synthetic oil.
I am a little concerned now after reading above that it could bypass the filter but the engine runs perfect.
Instructor
Joined: May 2016
Posts: 178
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From: Vermont
As with any electric-based gauge system, it is imperative that the sending unit & gauge are "matched". That is, the sending unit must be designed for a matched gauge. I've seen erroneous readings several times with temp gauges when a replacement sending unit has been installed that is not matched with the gauge.
My opinion ? You're OK. You have a 40 year old gauge that was probably not exactly accurate when new. Check the pressure with a good quality mechanical gauge. (the best quality you can find. good ones are accurate to 2%. )
My opinion ? You're OK. You have a 40 year old gauge that was probably not exactly accurate when new. Check the pressure with a good quality mechanical gauge. (the best quality you can find. good ones are accurate to 2%. )
Le Mans Master
Joined: Apr 2015
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High oil pressure is not ideal as it puts a lot of stress on the distributor gear, robs horsepower, promotes oil consumption, leaks, and can suck the oil pan dry faster than the oil can drain back to the pan.
As others have stated I would confirm the pressure with a mechanical gauge.
As others have stated I would confirm the pressure with a mechanical gauge.
Burning Brakes
Joined: Apr 2008
Posts: 1,222
Likes: 93
From: shelbyville West Michigan
Mine is near 80psi as soon as the revs get above idle. Actually it is probably 70-75psi but if I give it a shot of gas it hits 80psi. This is on a hot day too.
I built engine for the correct oil clearance and I am running the Melling Z28 pump I have used on many engines. The engine has 20k on it now and the high pressure doesn't seem to seem to be causing any problems. I am running 20W50 Brad Penn semi-synthetic oil.
I am a little concerned now after reading above that it could bypass the filter but the engine runs perfect.
I built engine for the correct oil clearance and I am running the Melling Z28 pump I have used on many engines. The engine has 20k on it now and the high pressure doesn't seem to seem to be causing any problems. I am running 20W50 Brad Penn semi-synthetic oil.
I am a little concerned now after reading above that it could bypass the filter but the engine runs perfect.
stock filter bypass valve is 12-15 psi, so even a stock pump that puts out 35-40 psi is bypassing.
70-80psi is not the correct output for a stock motor with a stock pump, the pump bypass itself would be defective. high volume pumps can have different springs changed out in the pressure valve to increase pressure. the only time I would use a high pressure setup like that is with a race motor setup with very loose clearances for high revving. a situation most street motors never see.