Fail PV if high-pressure oil pump??
'66 L79 Vert #1241-- My mechanic told me I likely had a high pressure oil pump installed (before I bought it) because the oil pressure reads 70-80 psi all the time. Would I fail PV if that's true??
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Re: Fail PV if high-pressure oil pump??
yes. way too high at idle. mike -
Re: Fail PV if high-pressure oil pump??
Ouch-- how expensive a fix to replace??Comment
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Re: Fail PV if high-pressure oil pump??
remove oil pan and oil pump and replace with
low press pump. perhaps your mechanic has the low pressure spring, in which case just remove the high press spring from existing pump and install the low press spring. you'll need oil pan gasket and new pump or low press spring in existing pump. mikeComment
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Re: Fail PV if high-pressure oil pump??
Stephen,
Changing the oil pump would be in your best interest anyway as that much oil pressure at idle can pump all the oil in the valve covers and starve the oil pump. That in turn can cause no oil pressure at the crankshaft during high rpm runs. May sound wild that this would happen but it has been described by engine builders for years.
Rule of thumb is 10lbs per thousand rpms. That would be 60 lbs at 6000rpms. That is adequate oil pressure when you have your foot in it!
As Mike describes, it's a piece of cake to change the oil pump or change the spring. A piece of cake if you have a lift anyway. Changed more than on on a creeper! Less fun but not a problem when you are young.
JRComment
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Re: Fail PV if high-pressure oil pump??
Thanks, Mike. Guess I need to do it if I want PV award, so, plan to. Doesn't seem too expensive.Comment
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Re: Fail PV if high-pressure oil pump??
Wow-- You (Joe), may have diagnosed a problem I had. The engine runs fine, but recently I "tached it up" (5200 rpm) for the first time and had a temporary "clacking" sound for +/- 2 minutes, that didn't go away until I revved it up again to 5200 RPM. I feel no decrease in power after this event, and no valve noise, so I'm drawing the conclusion that at high RPM's I had starved the crankcase of oil, as you said (I'm having my mechanic check for compression and valve damage just in case).
ThanksComment
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Re: Fail PV if high-pressure oil pump??
Stephen,
You experienced a loss of oil pressure to your hydraulic lifters and the clacking was present until the oil pressure was returned.
Do not repeat that exercise until you have explained what you did to your mechanic and he fixes your oil pump problem. Permanent damage could (will) result from loosing oil pressure internally.
JRComment
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Re: Fail PV if high-pressure oil pump??
Great, cautionary advice, all-- begs the question, though why DO engine (RE-) builders use the high pressure oil pumps if they're potentially damaging-- is it to cover up some shortcoming (low pressure equating to engine needing rings or valves) or, just the impression that more oil pressure= healthier engine to potential buyers???
ThanksComment
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Re: Fail PV if high-pressure oil pump??
over the years, when i've rebuilt sbc and bbc, the new oil pumps have come with th high press spring installed in the pump and included in the package was a low press spring. its a simple chore to switch springs. mikeComment
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Re: Fail PV if high-pressure oil pump??
[QUOTE=Joe Ray (1011);687396 Rule of thumb is 10lbs per thousand rpms. That would be 60 lbs at 6000rpms.
This "rule of thumb" is for [U]racing engines[/U] and dates to back to at least the seventies.
All Gen I small blocks other than late '63-up mechanical lifter engine have normal hot oil pressure spec of 40-45 psi, and Corvettes with this "standard oil pressure" have 60 psi gages. The above specified mechanical lifter small blocks should have 80 psi gages. Even with the 40-45 psi relief spring mechanical lifter engines have no issues with occasionally revving to 6500+.
Another issue here may be that the pump is also of a high volume type. All small blocks should have a standard volume pump. The high volume pump is for loose-clearanced high revving Gen I racing engines, but all too many end up in road engines where all they do is heat up the oil and consume power and fuel pumping oil that is diverted through the bypass valve back into the pump inlet - the equivalent of a dog chasing its tail.
Current 9500 rev NASCAR engines only run 30-35 psi in order to minimize oil pump power absorption.
DukeComment
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Re: Fail PV if high-pressure oil pump??
[Stephen,
The collapse of a hydraulic lifter above 5K was common in the 50's & 60's and we usually only reved to 5K. Then we learned to adjust the hydraulic lifters to O lash (just till the clatter stopped) and we could rev to 5500. 5500 didn't really do much better as the power curve was less that 5500 in daddys car, but it stopped the collapse. Solids were the fad & much better and if you didn't put a mechanical cam in, some guys would put solids on a hydraulic cam if you can imagine that. Todays hydraulics are much better.
DOMComment
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Re: Fail PV if high-pressure oil pump??
As Joe said, the #3814903, 40-45 psi, spring is still available. Just picked one up at my local Chevy dealer last month, although the list price is $5.77 now.Comment
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Re: Fail PV if high-pressure oil pump??
Stephen:
Did your mechanic verify your oil pressure by using another gauge? If he didn't, I would check it before opening up your engine. It is a simple enough process.
BobComment
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