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hello I have a 72 with the basic engine ,driving down the road the oil pressure is well about 35 lbs ,around 40 ,but when im at a stop it drops down to about 15 or 20 lbs ,just when its idling, any concerns???
The oil pressure also depends on the engine temp and the type of oil that's being used.A 10w 30 will show a lower PSI than a 15w40.My hotrod has a BB mopar in it and when I built the engine I installed a normal pressure high volume oil pump so my oil pressure at idle at 180 degrees is 20 and as soon as I get above an idle it's at 75 .
If you look in a repair manual, you will not likely see an oil pressure specification at idle. Most manuals specify a pressure at 2k rpm or thereabouts. It's not that idle oil pressure is irrelevant, but that there are too many variables to set such a standard. The load on the engine is also very low at idle and as long as there is some pressure, that is usually sufficient.
There are very few folks on this forum who will remember this, but back in the dinosaur days, it was quite common for the oil pressure light to flicker at idle. The idiot light sender had a trip point of around 5-7 psi. The solution was not to overhaul the engine, but to raise the idle speed by 50 or so rpm or just ignore it.
If you look in a repair manual, you will not likely see an oil pressure specification at idle. Most manuals specify a pressure at 2k rpm or thereabouts. It's not that idle oil pressure is irrelevant, but that there are too many variables to set such a standard. The load on the engine is also very low at idle and as long as there is some pressure, that is usually sufficient.
There are very few folks on this forum who will remember this, but back in the dinosaur days, it was quite common for the oil pressure light to flicker at idle. The idiot light sender had a trip point of around 5-7 psi. The solution was not to overhaul the engine, but to raise the idle speed by 50 or so rpm or just ignore it.
Exactly!
Last edited by Redhook98; Jul 21, 2016 at 09:40 AM.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I currently have a Mellings HP/HV pump and initially used the stiffer of the two springs that came with the pump. On startup, the oil pressure gauge was pegged hard right and at normal temps 70 psi at cruise. I don't need that high of pressure so I used the other spring which gives me "normal" oil pressure for a sbc.
If this bothers you guys we regularly fly small Continental engines all over the country with 30 psi in cruise and 10 at idle air cooled so they have huge clearances. My 383 idles at 30 and cruises at 50, I seem to remember an old rule of thumb that 10 psi per thousand rpm is a good number to live with.
A) Is this according to your stock oil pressure gauge?
B) What RPM are you idling at?
If you REALLY want to feel better, I would hook up a cheap new oil gauge and get a fresh reading. I would put a dollar to a doughnut that the pressure is actually higher than what is indicated on your gauge. I'd prefer KNOW than speculate, though.
That isn't necessarily a good or bad thing. 15 PSI isn't the end of the world. My builder prefers 20 PSI, but he is OK if mine drops to 16 or 17 at idle after "spirited driving" heats up the oil. It returns to 20 PSI after puttering around in "normal mode" for 5 or 10 minutes.
I actually set my normal idle to 20 PSI of oil pressure. Turns out to be about 800 RPM. When I pull my engine during my frame swap, I will change springs in my pump to get a little more pressure at idle, allowing me to drop my RPM a smidge and REALLY get my cam lope to 'come out and play'.
I had wonky readings on my stock gauge not too long after rebuilding my engine. Everything sounded fine otherwise, so did the "ghetto oil gauge" thing from above. My builder had one laying around. Turned out all was fine. I ended up swapping over to AutoMeter gauges shortly thereafter...they work, and look, much better than stock. In my opinion, of course. Not the working...that's fact. But I think they look pretty darn sharp.
The tubing in the foreground is the oil line running to the pickup and wrapping around my windshield pillar.
Whatever works...
Last edited by keithinspace; Jul 21, 2016 at 02:27 PM.
Yeah, really! How much oil pressure do you think you need?
I am very happy where it is now. In our 468 circle track engine we run 65 psi at idle with a 10 quart dry sump and 20w50 Royal Purple. When the oil heats up to 230f or so we still have 40-50 psi to race on. You can call 15psi normal all you want but it is not for me.
Oil pump design for stock V8 Chevy engines requires roughly 10 psi increase per 1000 rpm with an idle pressure of 15-20 psi. When idling, 15 psi is plenty to lubricate a non-working engine. In addition, the engine is not doing unnecessary work, so it's not burning extra fuel to make extra oil pressure and flow than the engine needs.
For those with racing oil pumps, glad you are happy with them. You will get plenty of oil and plenty of pressure. But, for a street car, you will get much more of each than is necessary. The oil pump in my '71 coupe's SB engine works just as mentioned above...and it has done so for 216K miles. The engine has had one full rebuild and another head re-do because of a stuck heat riser valve and head gasket failure. NO problems due to insufficient oil volume or pressure.
Racing engines (which actually race) NEED better oil pumps because of the continuous level of hard work the engine is doing. Most of our street vehicles don't. But, of course, everyone should do as they choose with their vehicle.
Last edited by 7T1vette; Jul 21, 2016 at 11:45 PM.
Likewise my '77 (odometer says 44 thousand) tends to be 25 at idle with a hot engine, water at 185 to 195 F. And it has dropped to 20 when hotter, around 200 degrees.
Driving at highway speeds above 50 MPH it stays close to 35, and 40 if not fully heated yet or at higher RPM. So 25 to 35 is what I usually see on the gauge.
Seems like it increased a little after putting in a bottle of STP oil additive containing ZDDP. Otherwise oil is only 10W 30; will be 10W 40, or possibly 20W 50, later on so I can compare.
((((( oil pressure )))))
