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Discussion Starter #1
I recently re-built the top end of my 350. New heads, cam, intake etc.
The engine runs great however, the oil pressure is low. 30 PSI cold and
10 -20 warm at idle.
Thoughts?
 

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I would consider 10-20 psi at warm idle to be perfectly acceptable.
 

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I would consider 10-20 psi at warm idle to be perfectly acceptable.

Ditto....

What weight of oil are you using? If 30 weight, go 40. It will raise it to a level you are more comfortable with. Had to do that when I installed the EDM hole lifters for my solid cam.
 

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Cardfan16:

If you went to all that trouble to do the top end I would recomment that you pull the oil pan clean it and replace the oil pump with an HV55 high volume and a new pick up. If you have done a lot of top end work on an older motor a lot of crud can brake / flake off and find its way to the pick up screen. Replace the pump drive shaft with a steel sleeve type also. You will be impressed with you oil PSI after that!!:thumbsup: :beers:
 

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What weight of oil are you using? If 30 weight, go 40. It will raise it to a level you are more comfortable with. Had to do that when I installed the EDM hole lifters for my solid cam.
 

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I guess it depends on what you are comfortable with....as onovakind an wildman said, you should be fine. I've always heard, as rule of thumb, 10 PSI for every 1000 rpm, which you have. It is disheartening though to pull up to a stop sign, and see the oil psi drop way down... I would try a different weight oil and see if that helps.
 

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Discussion Starter #9
I'm using 15-40 wt oil. The engine runs at about 200 f when warm here in AZ. It concerns me to see the oil pressure so low at idle.
 

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I'd prefer to see more too, but what you have is acceptable.

Oil pressure is determined by pump volume and how big the holes it leaks out of are, that is, the bearing clearances. If I went to the trouble of opening up the bottom end, I'd do a ring and bearing job on it in addition to the new oil pump.
 

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keep in mind if you were using reg synthetic oil and changed to royal purple etc. youll have a significant drop in pressure.
I had a 15 psi drop when i changed to royal purple and thought I was having problems but after 5 years the car still runs great!:D
 

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a chevy will run fine on 5psi. How do I know? drag racers run their engines 2 quarts low most of the time, and explained to me that a CHEVY doesnt need a lot of oil pressure because of its design. AMC? completely different story....
 

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I changed 2 synthetic and my car idles around 8-10psi at idle at 190deg. im happy with that.
 

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I like good oil pressure.
But I've had lots of great engines that didn't seem to care.

If you are keeping your hydraulic lifters pumped up,and the pressure comes up with RPM, you have all you need.

Oil pressure, like Jim said is a function of volume and losses.
Oil pressure is what you are supplying to the surfaces. It is not what gets the oil into the journals. That is accomplished by hydrodynamics. The rotating shaft pulls the oil into the clearance. It would require in excess of 50,000 psi to inject oil into a journal according to manufacturers and engineers. So, if your oil pressure rises with RPM, your delivery is capable of exceeding demand. Hope that makes sense.

It makes sense to me, and I work on million dollar machines everyday that have oil pressure within spec or we take em apart. Sometimes the spec is apallingly low to imagine a $50,000+ crankshaft being trusted to it. But I PREFER good oil pressure. And so do lots of our customers. I have seen tens of thousands of dollars spent in search of "good" oil pressure. Sometimes we never find it, and just have to live with it being at the low end of spec. because the contributing factor (crankshaft) in the system is at low end of spec. but doesn't require replacement.
Later
Tim
1977 Camaro, Wolf by name
412 SBC, no juice or brake yet, 10.85/126mph
75#cold/60#warm/ 45# hot idling or I take it apart
 
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