to much oil psi
After my 66 L79 is warned up it idles at 50psi, but going down the road at 55mph the guage is past the 60 on the guage as far over as it can get. Is this to high? thanks Terry
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Re: to much oil psi
I wouldn't think so. My Trans Am cold is between 75-80 cold and around 55-60 driving. On long hot drives it finally gets down to 45. I just make sure not to rev it until warmed up so I never see my needle go past 80
It depends allot on the type and weight of the oil, exactly how long it's been at operating temp, and how many miles are on the oil. You could always go down on the oil weight. Too thick can actually be bad and prematurely wear the bearings but you don't want to be too thin if you have a loose piston bore either.
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Re: to much oil psi
You'll get varied opinions but feel engine is getting way more oil to the top end than it was designed to receive. You didn't state if the pump is new or has been changed so I'm assuming pump has been in the engine for a while? If so, what has been the past readings? Being a hobbyist engine builder feel that too many engines have way more oil pump pressure than is needed. A good standard oil pump is all that most engines will ever need.Last edited by Michael G.; July 10, 2011, 03:27 PM.Comment
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Re: to much oil psi
As others have mentioned, it's possible that the engine has an oil pump that was designed for the mech lifter engines and is developing more pressure than you need. It's also possible that the oil selection is a partial factor.
I know that 15w40 Rotella will cause the oil pressure to be higher than it should be, even with a correct oil pump/spring.
If you're using 15W40, the first thing I would do is switch to 10W30 and see if the pressure drops to a more normal range.Comment
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Re: to much oil psi
Hi, the engine has less then 100 miles on rebuild, I have 10w30 in it, I had it rebuilt so I don't know what kind of oil pump was used. I couldn't stop the oil filter from leaking but it was a repro, I just installed the old one and see if that stops leaking. I was just thinking to much presure may be the cause.Comment
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Re: to much oil psi
Is filter spin on adapter type or original canister regardless more than likely a fittment issue of adapter or possible a stuck canister gasket.
Sound like a high pressure oil pump Terry. Does your paperwork from mechanic indicate any info on pump?Comment
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Re: to much oil psi
Bubba the engine builder put a high volume, high pressure pump in it, and the 10W-30 oil is probaby SN. Sounds like the guy is clueless. He probaby did some other bad things, too.
Oil viscosity range is not a big factor in oil pressure; 15W-40 CJ-4 runs about the same in my cars as the 20W-50 S-category did a decade ago.
The excessively high oil pressure, in and of itself, should not cause a leak.
DukeComment
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Re: to much oil psi
Mine runs a tad higher with the 15wx40 Rotella, but more as a matter of less fall off when full warm than with 10wx30.
Stu FoxComment
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Re: to much oil psi
The service category is more important than viscosity and a few psi oil pressure.
For small blocks (except late '63 to '65 versions with mechanical lifter cams) Chevrolet's hot oil pressure specification is 40-45 psi at 2000 revs (and it should not go higher with increasing revs), but check your year AMA specs to be sure.
Chevrolet has no specification for idle oil pressure, and it is highly dependent on idle speed and engine oil temperature. So a 300 HP/Powerglide idling in Drive at 450 may only show 15-20 while a 350 HP idling at 750 in neutral may show 25-30, both with the oil temperature at about 200, which is typical of normal driving in 70-80 degree weather.
DukeComment
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Re: to much oil psi
Terry,
I think it's way to much oil pressure, your engine should have a 45psi relief spring in the oil pump. I have read 10 lbs for each 1000 rpm increase so you are pushing alot of oil through the engine that's not needed.
The oil pressure can still be high on a stock rebuild at idle depending on main and rod bearing clearance but the pump will relieve at the 45 psi spring setting so it will maintain that pressure, as Duke posted the GM spec is 45psi @ 2000rpm. It's probably a Melling pump, they seem to run higher relief pressures but they are good pumps.
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Re: to much oil psi
I have a older Melling M-55 pump that I have checked the end clearance at .001-.002 and I am going to make a block off plate for the output side that has a threaded fiutting for oil pressure gauge. I plan to spin it with a drill press and add a supply tube so I can check relief pressure of any oil pump from here on that I install on a small block.
I will install the GM 45 psi spring in the pump first to see if that gets it done and if not I will trim the Melling spring to see if that will bring relief pressure in spec where I like it. All I want is 45 lbs for my cars and I know my 67 will probably maintain that at 16-1800 rpm and up. My 63 has approx 20-25 psi at idle and takes higher than 2000rpm to hit the relief at 45. The 63 has a GM pump and you can watch the gauge stop at approx 45. The 67 has a Melling and I am not happy about the relief pressure but I don't feel like removing the pan again.Comment
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