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Hi Folks - Please help confirm what the normal oil pressure is for a small block when warmed up. I seem to recall that normal is about 40 psi at 1500 rpm, and I think that I saw that reported in "Car Life" magazine road tests back in the day.....
(I wish I could confirm this myself, but the 327 is presently out of my 1966 for rebuild.)
When I 1st start it up it pegs past 60. After it warms up, driving around town, it's around 40, and pretty much stays there. I was trying to think what it is at idle, I want to say 30 as it does not, I believe drop below that.
The engine was rebuilt when I got the car and I mean just sitting in it. I/we took it apart as I did a complete res-to-modernise of the car since it was in boxes when I got it. The engine upon inspection was rebuilt as new, and all the parts appeared to be new. The oil pump was brand new, I just inspected it and that was about it.
I hope this helps, by the way, do you have a manual, it my be of help.
Dennis
I use the rule of thumb on this and say 10psi per 1000RPM, I like to see maybe a bit more at idle or under 2k on a tight or fresh motor....this is after everything is warm and oil temp is 220+
My smallblock runs these sort of numbers, there is of course some variation as the motor runs up, it tends to build a bit faster then slows
as speed increases...pretty much what I'd expect.
If you're talking FACTORY specs, then it depends on the engine option. Also, the oil pressure gauge is dependant on the engine option.
The lower performance engines had a 60lb gauge and ran about 35lbs after the engine is fully warmed up and everything is normalized.
The hi-perf engines ran at about 60lbs and had an 80lb gauge.
Basically, the difference between a low and hi-perf engine/gauge was a hyd lifter cam vs solid lifter cam engine.
Basically, the difference between a low and hi-perf engine/gauge was a hyd lifter cam vs solid lifter cam engine.
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And the only difference between the small block standard pump and hi-perf pump is the spring behind the bypass valve. On the big blocks, the only difference is also the spring, except for the L88 & ZL1 pumps--They used the same spring as the SHP pump, but the pump was physically larger--higher volume. Both small block pumps are physically the same size.
I sent this info. to Bob, but thought someone else may want to know.
Bob did a some research for you and could not find anything that discussed oil pressure in any of the usual sources.
I know I had seen it and then remembered where, in a packet I sent away for after someone in the forum advised us that this information was available free of charge for a 63-67. I requested info. for a 65. Someone out there may remember the e-mail address. I rec. it in about a month. There are two parts, the 1st was for resources and contacts, the 2nd are the specifications, I think it's more complete then any of the so called manuals. I don't remember this as the contact, but this is on the return address MSX International PH.NO. 313 203 5106.
The Information is as follows. Oil pressure for 250-375 hp normal oil pressure {lbs @ engine rpm} 30-45 PSI @ 1500 exactly as written.
I have a 350 small block Blueprint Engine with an electronic oil pressure gauge.
My oil pressure range is between 55-70.
Is this good?
For MANY, MANY years, there has been TONS of discussion, debate, disagreement, conflict, etc, etc, etc, regarding a hi-volume/hi-pressure vs std pressure oil pump. I have never been sucked into these discussions. All I will say is that ALLLLLLLLLLLLL my engines (INCLUDING the granny grocery getter engines) get a hi-vol oil pump.
I've been building my own engines (and for other people) for over 50yrs with ZERO issues resulting from a hi-pres or hi-vol oil pump. Once thoroughly heated up and normalized, most of my engines have about 55-60psi oil pressure.
Yeah, I gotta agree with that. There are a few of us that put BB oil pumps in SBs based on a 50 year old book, supposed to have less pressure pulsation bc of more teeth on the gears.
Bear in mind that even electronic gauges can be wrong. That said, unless the oil is squirting out of the rear main or other seals, you should be in fine shape.
I have to admit why i have a ton of parts in my garage and is thinking about a 427 longblock is because the car i bought 4 months ago when it is at idle has 16 maybe 17 pounds of oil pressure and that's with 20w50 Vr1 oil which sort of freaks me out, runs good for a little 327 but i have had many 350;s and they never had less then 30 pounds at idle
But then you type in my 327 has low oil pressure at idle and you will get tons of people who will say there 327 had 15 pounds oil pressure and ran for 200000 miles . so go figure
If your goal is to be NCRS approved you want what they look for, which is about 30-35 at idle or something close to that. They doc you if your pressure is higher or lower than what they want.
Oil pressure is a result of the internal clearances on your Main and rod bearings and clearance on the camshaft bearings. For many years now I target Main and rod clearances at .002 which is tighter than the old factory allowable clearances but works really well. With a tight engine you will have oil pressure at idle that matches your pump oil pressure relief setting. If the pump has a 55 PSI spring in it you will have 55 at idle or very close to that. In a good engine/tight your oil pressure relief is already opening by 400 RPM normally. Even a standard oil pump can keep good pressure at idle with tight clearances., The looser your bearings the more oil spills at idle and the more oil it takes to cover for those spills. If your engine makes 30 PSI hot idle but 55 PSI at 3000 RPM you absolutely know there are loose clearances somewhere in that engine. Cam bearing clearances are the hardest to control since not all blocks have straight cam bosses many engines have the bearings carved for clearance and there is nothing to do about this. A high volume pump covers up clearance issues very well by supplying more oil in normal operation. It does take more HP to spin a High Volume pump than a standard volume pump., How much is hard to say but I have heard numbers of 6-20 HP at high RPM.
In the 80’s and 90’s almost all engine builders offered the High volume pump as an upgrade and a lot of people used them.
When I build a tight engine the oil pressure is very nice and steady. Very little fluctuation with RPM. Loose engines may see 30 PSI fluctuation with RPM. Both engines will last a full life with no issue but I prefer the tight engine and I know it will fail NCRS because back then most engines were loose from the factory compared to todays standards.
Back in the 60’s and 70’ GM claimed any engine with 7 PSI or more at idle met their standards and were not a warranty issue. I would scream bloody murder if my new engine only had 7 PSI at idle but GM said it was fine.
Cold Oil does not flow well so it leaks less so a loose engine has much better oil pressure on cold start than it does once warmed up.
So, NCRS says you want 30-35 PSI but I prefer at least 40 ( and I am fine with 60 ) at hot idle and like knowing as the engine wears some I will still have plenty to cover demand.
One other affect not often thought about with loose bearing clearances. Rod bearings throw oil off on to your cylinder walls. Loose bearings throw 4 times or more oil on the cylinder walls., This can over work the Oil RIng and create an engine that uses oil. Just food for thought.
Mark
Very few cars around still running on the 60s GM-installed original oil pumps, or with original GM built engines, with GM clearances, with 60s spec oil and OE parts, etc. So, normal is a pretty illusive concept all these years later. I would never have guessed NCRS got so far into the weeds as to evaluate your oil pressure. Do they measure your oil temp and viscosity too when evaluating that? All I worry about is having around 20 psi at hot idle and a minimum of 10 psi for every 1000 rpm’s.
Many years ago, on ALL my engine builds, I have added an oil pressure gauge directly to the engine block coming off one of the oil galleys (to hell with NCRS correctness). This allows me to see exactly what the pressure is at any engine rpm/heat range.
I use oil filled gauges (for vibration dampening). If a NON-oil filled gauge is used, the engine vibration will eventually cause the gauges mechanism to fail.
10-17-2007, 11:40 AM
Normal C2 Small Block Oil Pressure??
Yeah, I gotta agree with that. There are a few of us that put BB oil pumps in SBs based on a 50 year old book, supposed to have less pressure pulsation bc of more teeth on the gears.
