Oil pressure to high??
Thread Starter
Racer
Joined: Oct 2007
Posts: 284
Likes: 6
From: Palm PA
Oil pressure to high??
My previous 350 had 20 lbs. at idle with 20/50 oil. My new 383 has 70 lbs. at idle cold with 10/30 oil, 50 at idle warm, 2000 RPM is 60 lbs. and 3000 RPM or over it's pegged at 70 lbs. Is this too high? I'm going to change the oil to 5/30. Is this normal for a new engine? It has a stock oil pump and a roller cam, lifters, and rockers. There are no valve train restrictions. Priming the new engine I had oil at the push rods. What's your opinion?
68 Vetteman
68 Vetteman
Race Director
Joined: Mar 2006
Posts: 14,112
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From: Florida
30 is your hot viscosity.
Your new engine just has tighter clearances and is going over the relief at 70psi.
Only remedy is to go lower is oil viscosity.
It will probably drop off a bit more with more miles anyway just make sure it's not running hot.
Your new engine just has tighter clearances and is going over the relief at 70psi.
Only remedy is to go lower is oil viscosity.
It will probably drop off a bit more with more miles anyway just make sure it's not running hot.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
My previous 350 had 20 lbs. at idle with 20/50 oil. My new 383 has 70 lbs. at idle cold with 10/30 oil, 50 at idle warm, 2000 RPM is 60 lbs. and 3000 RPM or over it's pegged at 70 lbs. Is this too high? I'm going to change the oil to 5/30. Is this normal for a new engine? It has a stock oil pump and a roller cam, lifters, and rockers. There are no valve train restrictions. Priming the new engine I had oil at the push rods. What's your opinion?
68 Vetteman
68 Vetteman
Thread Starter
Racer
Joined: Oct 2007
Posts: 284
Likes: 6
From: Palm PA
68vetteman
Thread Starter
Racer
Joined: Oct 2007
Posts: 284
Likes: 6
From: Palm PA
68 Vetteman
Racer
Joined: Nov 2010
Posts: 310
Likes: 25
From: Brisbane Australia
I posted a similar question about the same issue with my slightly less fresh engine the other day here http://forums.corvetteforum.com/c3-t...near-70-a.html
Based on the feedabck from that and some more research I'm going to be checking the bypass under the filter first to see if that is stuck.
Based on the feedabck from that and some more research I'm going to be checking the bypass under the filter first to see if that is stuck.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
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Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
First move you might want to make is to hook up another gauge, just in case.
Then, if NO high-volume / high-pressure pump I'd sure inquire with the builder as to the main and rod bearing and side clearances. Either they're too tight and/or the relief spring isn't standard. You really shouldn't have that much pressure with 30 weight if everything is done right. FWIW, running thinner oil could well increase usage.
Hope you don't have to go there, but you could end up having to pull the pan here...
edit - Excessive pressure isn't insurance. It saps power, puts more strain on related components, and puts additional heat in the oil. 10 PSI for each 1000 RPM is enough to overcome centrifugal force at the mains (a key factor) and supply adequate lubrication for most any SBC or BBC.
Then, if NO high-volume / high-pressure pump I'd sure inquire with the builder as to the main and rod bearing and side clearances. Either they're too tight and/or the relief spring isn't standard. You really shouldn't have that much pressure with 30 weight if everything is done right. FWIW, running thinner oil could well increase usage.
Hope you don't have to go there, but you could end up having to pull the pan here...
edit - Excessive pressure isn't insurance. It saps power, puts more strain on related components, and puts additional heat in the oil. 10 PSI for each 1000 RPM is enough to overcome centrifugal force at the mains (a key factor) and supply adequate lubrication for most any SBC or BBC.
Last edited by TheSkunkWorks; Jul 6, 2011 at 03:31 PM.
Thread Starter
Racer
Joined: Oct 2007
Posts: 284
Likes: 6
From: Palm PA
First move you might want to make is to hook up another gauge, just in case.
Then, if NO high-volume / high-pressure pump I'd sure inquire with the builder as to the main and rod bearing and side clearances. Either they're too tight and/or the relief spring isn't standard. You really shouldn't have that much pressure with 30 weight if everything is done right. FWIW, running thinner oil could well increase usage.
Hope you don't have to go there, but you could end up having to pull the pan here...
edit - Excessive pressure isn't insurance. It saps power, puts more strain on related components, and puts additional heat in the oil. 10 PSI for each 1000 RPM is enough to overcome centrifugal force at the mains (a key factor) and supply adequate lubrication for most any SBC or BBC.
Then, if NO high-volume / high-pressure pump I'd sure inquire with the builder as to the main and rod bearing and side clearances. Either they're too tight and/or the relief spring isn't standard. You really shouldn't have that much pressure with 30 weight if everything is done right. FWIW, running thinner oil could well increase usage.
Hope you don't have to go there, but you could end up having to pull the pan here...
edit - Excessive pressure isn't insurance. It saps power, puts more strain on related components, and puts additional heat in the oil. 10 PSI for each 1000 RPM is enough to overcome centrifugal force at the mains (a key factor) and supply adequate lubrication for most any SBC or BBC.
68 Vetteman
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
There is no real mystery here. Your oil pressure varies with operating temperature and rpm. Almost all oil pumps have a relief valve set at 70psi and that is why that is your max pressure. If the psi stops at 70, then it is not stuck.
You can check it with another gauge, but it will probably read very close.
You can change to a 180° tstat to warm up the engine a bit, no reason to run below that.
You can cut a slot in the dist to spray the cam/dist gear and/or also drill the front galley to spray the timing chain. Both will lower your pressure a bit. No downsides to this.
Put a quality oil filter on it.
The only time oil is heated unnecessarily is when it runs over relief , so if you're showing 70psi on the gauge it could be 70 or 85 psi, no way of knowing.
If the engine sounds good and runs well and you have lots of oil to the rockers, then just put some miles on it and the pressure will go down after some miles.
You can check it with another gauge, but it will probably read very close.
You can change to a 180° tstat to warm up the engine a bit, no reason to run below that.
You can cut a slot in the dist to spray the cam/dist gear and/or also drill the front galley to spray the timing chain. Both will lower your pressure a bit. No downsides to this.
Put a quality oil filter on it.
The only time oil is heated unnecessarily is when it runs over relief , so if you're showing 70psi on the gauge it could be 70 or 85 psi, no way of knowing.
If the engine sounds good and runs well and you have lots of oil to the rockers, then just put some miles on it and the pressure will go down after some miles.
