Is oil pressure really supposed to be that high?
Thread Starter
Teching In
Joined: Jul 2017
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From: Austin, TX
Is oil pressure really supposed to be that high? Just got a 94 formula and at start up the gauge on the dash shows 60psi of oil pressure, after warming it lowers to about 40psi. The car has 118k miles on what I assume is the original motor, can the oil pressure really be that high or is my gauge jacked? Planning on getting a mechanical one soon...
40psi is too high for hot idle. Normal is 15-25psi. It will take a good bit of driving for the oil to fully warm up. Gauge/sender is messed up or someone put in a HV pump. That or maybe someone put in a super thick oil.
Thread Starter
Teching In
Joined: Jul 2017
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From: Austin, TX
Yeah I was thinking the gauge is off, it does not fluctuate nearly enough when you rev the motor. Where is the best place to install a mechanical gauge? I have heard that there is a spot above the oil filter where the 93s had their oil pressure gauge that on the 94s is blocked off, would that work?
Also I have not changed the oil since I got the car so it could be that the oil in it is wayyy too thick. I am hoping that is not the case though because that means somebody is trying to hide something.
Also I have not changed the oil since I got the car so it could be that the oil in it is wayyy too thick. I am hoping that is not the case though because that means somebody is trying to hide something.
That's all of course if the gauge is accurate in the first place, which it's probably not.
Thread Starter
Teching In
Joined: Jul 2017
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From: Austin, TX
Genuinely curious, but why do you consider 40 too high? Do you have some documentation to show that? Mine sits at about 35 at operating temp, 60 when cold. That's at ~110k miles, stock pump w/ white spring, brand new AC Delco pressure switch, and 5w30.
That's all of course if the gauge is accurate in the first place, which it's probably not.
That's all of course if the gauge is accurate in the first place, which it's probably not.
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PS HV pump shouldn't change pressure much, A High pressure pump will though.
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Verdad Gallardo The relief pressure spring has absolutely nothing to do with your oil pressure at idle. That only comes into play when you hit the relief pressure set by it which would be 58psi for a stock spring and 70psi for a high pressure spring. Once that threshold is hit, oil goes out of the relief valve in the pump and dumps back into the pan. Changing the spring won't change your idle or cruising pressures. Increasing volume will do that.
40 at idle is too high because the pressure should raise another 15-25psi when cruising. You will be near or on the relief while driving around normally which is a lot of strain on the drive and will ultimately chew the gear. Beyond cruising to WOT, you're not going to build any more pressure from there because the relief valve will already be open. All you're doing is pushing super heated frothy oil back into the pan for no reason. It turns your crankcase into a mess, creates windage issues, and causes cavitation within the pump. HV pumps get a bad rap because they cavitate from hitting the relief too early, not from sucking the pan dry. The latter is a common misconception. This is why you only run a HV pump with a motor that has loose enough clearances to warrant it.
15-30psi is the sweet spot. The pressure raises when cruising but doesn't hit the relief too quickly. My motor uses a 10% HV pump, has loose clearances, and sees about 25-30psi at hot idle depending on oil/season. Put a pressure gauge on your motor and check it the right way. Never trust the gauge cluster.
40 at idle is too high because the pressure should raise another 15-25psi when cruising. You will be near or on the relief while driving around normally which is a lot of strain on the drive and will ultimately chew the gear. Beyond cruising to WOT, you're not going to build any more pressure from there because the relief valve will already be open. All you're doing is pushing super heated frothy oil back into the pan for no reason. It turns your crankcase into a mess, creates windage issues, and causes cavitation within the pump. HV pumps get a bad rap because they cavitate from hitting the relief too early, not from sucking the pan dry. The latter is a common misconception. This is why you only run a HV pump with a motor that has loose enough clearances to warrant it.
15-30psi is the sweet spot. The pressure raises when cruising but doesn't hit the relief too quickly. My motor uses a 10% HV pump, has loose clearances, and sees about 25-30psi at hot idle depending on oil/season. Put a pressure gauge on your motor and check it the right way. Never trust the gauge cluster.
TECH Regular
Joined: Apr 2013
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You are GOLDEN! When my factory LT1 was going on me, the oil pressure on idle was 15 PSI to 10 PS1 per my factory gauge. It was verified when I installed a manual oil pressure gauge on my pillar arm.
Ever since I had a remanufactured LT1 put in, the cold oil pressure is at 60 PSI and on idle, 40 PSI. When driving on the expressway it is at 20 PSI. Your engine is HEALTHY!
Ever since I had a remanufactured LT1 put in, the cold oil pressure is at 60 PSI and on idle, 40 PSI. When driving on the expressway it is at 20 PSI. Your engine is HEALTHY!
Thread Starter
Teching In
Joined: Jul 2017
Posts: 31
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From: Austin, TX
Thanks everyone for the input, seems like I need an oil change and a mechanical gauge and then I can see where the health of the motor is REALLY at, hopefully its good. I plain don't trust the gauge cluster, but ya never know it could be right....
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From: Tucker, GA
ERE 383 w/A4, 5w30, pretty new engine so its still tight. Hot oil pressure is 40-42 PSI at idle in neutral. 36-38 PSI hot idle, in gear. 10% HV Melling (10552). Previous ERE383 had over 10k on it and kept the exact same numbers throughout. As the oil change gets closer, these drop maybe 2 PSI.
1: The spring in the pump has zero to do with oil pressure at idle. That has been covered.
2: There is absolutely nothing wrong with 40 psi at idle. Ignore anybody telling you different. Most SBC Chevies I have had over the years had the same. But, thinner oil will lower the pressure at idle. 5W20 will certainly have lower pressure at idle than 30wt.
3: HV oil pump in a SBC, or LT1? Why?? Last engine on the planet that has the slightest need for that. One of the dumbest things I can think of.
Btw, GM says 5psi per 1000 RPM is all they need.
2: There is absolutely nothing wrong with 40 psi at idle. Ignore anybody telling you different. Most SBC Chevies I have had over the years had the same. But, thinner oil will lower the pressure at idle. 5W20 will certainly have lower pressure at idle than 30wt.
3: HV oil pump in a SBC, or LT1? Why?? Last engine on the planet that has the slightest need for that. One of the dumbest things I can think of.
Btw, GM says 5psi per 1000 RPM is all they need.
Lots of fast NHRA & IHRA Stock & Super Stock SBC guys are running low volume oil pumps. Standard volume pumps with shortened gears with a spacer. A very knowledgeable gentleman builds them. Frees up some hp, with zero problems. High oil pressure requires more power to turn the pump. My 350" LT1 goes 8300/8500 (depending on the weather) in the lights, with max 40 psi. Many of us doing it. Have for years.
You build a lot of competitive race engines?
You build a lot of competitive race engines?