Thread: SBC oil pressure?

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I just installed a freshly built SBC 350 into my rod. I put a high volume Melling oil pump in it. On start up for the first time the oil pressure was 80psi... expected, as it warmed up to 160-180 degrees oil pressure was around 40psi...ok not bad.

But as I let it get to around 200-210 degrees the psi was around 20psi.... This concerns me. That seems really low to me for a freshly built SBC with a high volume pump.

Now all these reading were taking with the car in idle. The pressure does rise with throttle, and will stabilize at steaddy throttle. Also, when I allow it to cool down and then restart it, the pressure still starts out around 60psi.

I guess what I'm asking is do ya'll think something is wrong, or is this type of pressure to be expected at idle and operating temp.

please share your experience, and maybe what my target psi should be for this situation if I have a problem. Thanks.

Johnny- have you let the motor break in completly yet? I had a simular experience with a melling pump I installed in a 327, after it broke in good it stablized out to 32 & 56. I was rethinking everything- did I clearence everything, what did I miss, I mean I was going nuts. It was the second oil change that did it. I guess that maybe some of the moly lube was still circulating.
Good Luck.

Your oil presure is consistant with a high Volume pump as in not high presure. You should be fine.

I haven't broken it in completely yet. I have probably only let it run for a total of 45min-1hr.

I can't think of any reason it should drop oil pressure. It is a brand new crank (not a regrind). Brand new harmonic balancer. Brand new Clevite HP bearings. New cam bearings. Brand new cam etc. Everything is brand new.

What weight motor oil are ya'll breaking them in with? Maybe I'm using something too thin? (10W40). I did use the moly lube very liberally... and I mean VERY liberally.... used a whole Jar of Redline assembly lube.

In any event, my confidence is a bit better.

Any other insight? Thanks.

Originally Posted by hambiskit

Johnny- have you let the motor break in completly yet? I had a simular experience with a melling pump I installed in a 327, after it broke in good it stablized out to 32 & 56. I was rethinking everything- did I clearence everything, what did I miss, I mean I was going nuts. It was the second oil change that did it. I guess that maybe some of the moly lube was still circulating.
Good Luck.

Read this thread; http://www.clubhotrod.com/forums/sho...lesson+learned
You may get a better understanding of your situation, which BTW, looks quite normal to me.

my sbc idles at 45-50psi oil pressure and its got a high volume pump.

Originally Posted by Bob Parmenter

Read this thread; http://www.clubhotrod.com/forums/sho...lesson+learned
You may get a better understanding of your situation, which BTW, looks quite normal to me.

Lots of good info, but still leaves the issue a bit foggy, especially with a lot of theory involved.

I estimate about 350-380Hp out of this motor. I am running a high volume oil pump with a stock depth oil pan. Would I have been better off running a regular oil pump or does it really matter? I am just trying to avoid a future problem.

I just don't want something to happen that merits that I end up having to pull this motor again and get it on a stand. I can replace the oil pump with the motor in the car..... if the high volume pump is a problem and might cause more harm than good.

Thanks.

BTW- I am not running a remote oil filter.... just the filter at the block.

Hard to say what happened to your Olds without doing a diagnosis of the failed parts. If in fact a high volume pump sucked up more oil than the rervoir (pan) could supply, and you sucked air from time to time, that may have contributed to bearing failure, if that's what happened. The thing is, the capacity of the pump, and the pan, are only a couple of factors. Just because the pump has the capability to pump more, doesn't mean it necessarily can supply more. You're still going to be limited by the oil gallery dimensions........the 5 pounds of s*** in a 2 pound sack example. In an oil system, if you over supply it will likely dump over a relief, or leak out somewhere/anywhere it can, but will it get back to the pump in time to keep it from starving the reservoir? I think folks go with high volume or high pressure (whichever they think is golden) because they operate from the "more is better" school of thought, rather than from any real need and/or understanding. If you have hogged out the galley, increased the bearing clearances, expanded the size of the total oiling system, e.g. the remote system, then a high volume pump might be justified to keep up with the larger volume changes to the total system. A high pressure pump makes no sense at all to me in a gasoline engine...........hydraulic system maybe, not an engine.

Right on BOB,Have always run stock MELLING GM replacement oil pumps currently have one in my 454BBl (50PSI from start up to shutdowne) run NAPA 10W40.old man runs same pump in his 468 BBL 1967 nova car runs 9,50's 1/4 136/137 MPH. SO at what point do you need a high valume pump I dont know. any way JOHNNY if it's going to keep you up at nights,spend $20.00 for a MELLING stock pump and forget about it.(FYI) If your pick up dosn't bolt to pump housing,after you install it have it MIG- welded to the pump,you run the chance of it falling off down in to the oil pan after a good hole shot,That will realy freak you out (NO OIL PSI)talking from first hand experience.

if it stays consistent with what you have now, you should be ok. when it start jumping all over the place then you my have a problem.