Does anyone know what the maximum oil pressure is you can run on a street driven sbc? I'm running about 110# at a cold idle with 5W30 synthetic, and no filter by-pass. All summer long I let it warm up until it came down to about 80# before I took off for fear of washing out my bearings. Something an old timer told me would happen. ???? After 10,000 hard miles the pressure hasn't come down any. Something I was hoping it would do.

------------------
49 year old kid in an 538 hp 415 84 Camaro

 

silly question but first thing i wondered is your gauge accurate? if it is i think i'd be worrying about too much oil preasure. sorry i don't know the answer.

------------------
-=ICON MOTORSPORTS=-

 

There is no need for anything over 80 psi, especially when you use synthetic (assuming it's a good synthetic, and not a "me-too" brand).

Like ede says, make sure your gauge is reading correctly first. If it is, you probably have a stuck pump pressure relief valve.

Just curious, rode51, do you run at Scribner? I haven't been out there since '84 while at UNL, but it was the only game around then.

------------------
82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, ported heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

[This message has been edited by five7kid (edited October 07, 2000).]

 

Yeah, you are running too much pressure. Like he said, check oil pressure with known good mechanical gage. If still high, could have blockages somewhere but it's more likely that hp bypass spring system is acting up. Don't run those HP springs, either. All they do is crank OP up at startup but when oil heats up, the max pressure attainable is USUALLY lower than that spring will allow, anyway. All they do is waste power.

 

There's nothing wrong with my gauge.
I know it's too much pressure, but will it harm the engine?
I've been to Scribner twice this year. It's got a new owner, and trying to make a come back. I ran low 12's on hard street tires, slipping, and sliding all down the track. I've got some 315/35-17 BFGoodrich Drag Radials to try now

------------------
49 year old kid in an 538 hp 415 84 Camaro

 

I don't know of any "maximum" oil pressure, as such. That is to say, nothing I know of is going to blow out or fail from it with the possible exception of the oil filter. I've never heard of "washing out bearings", and I can't imagine what that would refer to. Knowing that you're roughly as much of an old-timer as myself (I think we were both invented sometime just after dirt but well before soap) I'd like to know what the logic behind that is, if for no other reason than historical curiosity.

However, too much oil pressure will create extra wear on the dist gear in a wet-sump motor, and depending on your valve train gear, may cause more oil than necessary to get pumped up into the valve covers where it will just accumulate on top of the head and get hot. It could be a distinctly harmful thing in that way.

IMHO the numbers you are quoting are too high for a wet-sump SBC, in that they are more than the motor needs, without adding any benefits. If it were my motor, I would adjust that the next time I had access to the pump. My personal favorite combo is a stock pump (cheap - a great virtue) with the Mr. Gasket spring in it (also cheap), which usually seems to produce about 55-60 cruising and 30-35 idling in motors the way I build them which is with tight bearing clearances, as the one I'm driving right now does with the same oil you're using. I think that's enough for anything most all of us on this BBS are doing.

On a slightly different subject, what kind of trans & rear end are you running?

------------------
"So many Mustangs, so little time..."

 

An oil pump creates a constant pressure directly proportional to how fast it's spinning. It is a positive displacement pump (pushes the same amount that it pulls). The pump regulates the discharge pressure with a pressure relief spring and piston through a bypass port, back to suction side of the pump. As pressure builds when the pump speed increases, that pressure is applied against the pressure relief piston and spring. When the internal oil pressure of the pump against the piston overcomes spring's tension, the spring compresses. When the spring compresses, the piston moves and opens the return port, allowing the oil in the pump to re-circulate.

So, now that we all know how the pump regulates pressure, what do you think could be happening? I think the return port/spring/piston combination is not working as designed. Most likely a stuck piston do to contamination.

Do you have excessive oil pressure? Absolutely. 60-70 psi is all you will ever need.

Is the excessive oil pressure going to cause any problems? Only if you consider seals/gaskets leaking, excessive wear on the distributor gear, oil consumption through the pvc and oil pressure sensor damage problems.

If your using a HV/HP big block pump and you have tight bearing clearances, then expect to see 100 psi. Otherwise, the standard volume pump with a high pressure spring will be 60-70 psi at around 3500 rpm. At idle, 10-15 psi is normal and it should increase to 30-40 psi at around 1500 rpm.

Mike

 

Yeah, that 110psi is high, no matter what he says, and I would check it with another gage because I have never seen that high w a small block pump on a used/worn-in engine bearing set.

 

Can't say I agree with that description, at least the part inside the parenthesis. It's positive displacement because it pumps the same volume per revolution regardless of speed. Period.

I agree with everything else you say, and the above part about the oil filter being in danger. The rear seal can also be overwhelmed, but that's not as big a deal.

 

I was going to let this one go, but I changed my mind seeing you had to throw that "Period" in there.

Overhaul, repair and vibration monitoring of rotating machinery is what I do for a living. Have been for close to 20 years. Everything from little 50 hp electric motor driven centrifugal "non-positive displacement" pumps to 40 mega-watt turbine driven generators and Frame-V R/R and GE turbines.

Do you know what positive displacement means? Oh yeah, " it pumps the same volume per revolution regardless of speed". Hmm. Isn't that what I said? Just a little different verbiage, but same meaning. Positive displacement is simply this; what goes in, must comes out.

A positive displacement pump is either a gear, rotor, diaphragm, or piston type pump. Meaning, there is a mechanical means inside the pump that moves the product from point a to point b. In regards to "our" little oil pump, it is a "positive displacement gear type pump". The gears mesh together with very close tolerances between themselves and also the pump housing. This "meshing" creates a low pressure area (vacuum) between the meshing gear teeth and the suction side of the pump housing . Product (in our case, oil) is drawn into the teeth (on the suction side) and is carried away by these teeth to the discharge port of the housing. The close tolerances of the gears to the case keeps the oil "trapped" between the teeth and the pump housing. When the gears come in contact with each other again, the meshing of these teeth will force the trapped oil out of the teeth into the discharge port. Because of the close tolerances in the pump, all oil that is drawn in must be forced out =positive displacement. Period.

What I also said if you care to re-read my original post, is the PRESSURE will be directly proportional to the pump's speed. I'll re-phrase that for you. The faster the pump spins, MORE FLUID is drawn into and out of the pump which WILL create higher pressure. If a devise is not used to re-direct that increase in flow, pressure will continue to build until something gives. You will NEVER see a positive displacement pump without a devise that does exactly that, re-direct the discharge flow. It may be a pressure relief valve or a regulator. Both of these devises will either re-direct flow back to the suction side of the pump or to the reservoir that the pump takes suction from. Period!

Now back to the "at least the part in parenthesis" part of your rebuttal. "Pushes the same amount that it pulls". How could I have phrased it more simply so that anyone could understand the concept??? Obviously not simple enough.

To disagree is an expectable and expected form of communication. I am always open to disagreement and I'm sure to learn something new. To be an *ss while disagreeing, well that's entirely different. I'm not as open to it and will reply in a similar manor.

Should we continue with this subject? I write training, maintenance and operation manuals on this sh*t and have just got started. I'm sure that you could teach me a thing or two though.

 

everyones have way too much fun with this going to lock it to keep everyone out of trouble. if you wish to continue please use e mail. thank you.