Excessive oil pressure

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wilson1970
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Re: Excessive oil pressure

Post by wilson1970 » Sat Sep 22, 2018 9:05 am

I changed the Wix filter and put 10w30 valvoline in it yesterday. Dropped oil pressure to 55# after driving for 20 minutes or so. I do not have oil temps to report. This is more of an acceptable range.

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Re: Excessive oil pressure

Post by racear2865 » Sat Sep 22, 2018 11:00 am

Normally a HV pump will not make as much pressure as a High Pressure pump. The HV pump will only have a slight amount stiffer spring. It was never designed to make more pressure, It was designed to pass more volume if the clearances is larger than necessary. A HV pump can only pass as much oil as the clearances allow, no more. As the bearings began to wear, the HV has capability make up the flow loss. That is all. no more , no less.
reed

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Re: Excessive oil pressure

Post by Ed Wright » Sat Sep 22, 2018 11:56 am

gnicholson wrote:
Thu Sep 20, 2018 6:44 pm
you installed a hv pump and you dont understand why the pressure is to high with your stated bearing clearance?
Why would anybody put a high volume pump in a SBC??
http://www.fastchip.com/
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Re: Excessive oil pressure

Post by Kevin Johnson » Sat Sep 22, 2018 12:48 pm

Ed Wright wrote:
Sat Sep 22, 2018 11:56 am
gnicholson wrote:
Thu Sep 20, 2018 6:44 pm
you installed a hv pump and you dont understand why the pressure is to high with your stated bearing clearance?
Why would anybody put a high volume pump in a SBC??
Ask GM:
ZZ383_oil_pump.png
HV_oil_pump_PN93442037.png
https://www.chevrolet.com/content/dam/c ... 301295.pdf
https://www.summitracing.com/parts/nal-93442037
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Re: Excessive oil pressure

Post by gnicholson » Sat Sep 22, 2018 2:23 pm

racear2865 wrote:
Sat Sep 22, 2018 11:00 am
Normally a HV pump will not make as much pressure as a High Pressure pump. The HV pump will only have a slight amount stiffer spring. It was never designed to make more pressure, It was designed to pass more volume if the clearances is larger than necessary. A HV pump can only pass as much oil as the clearances allow, no more. As the bearings began to wear, the HV has capability make up the flow loss. That is all. no more , no less.
reed
first of all flow and pressure are part of the same formula. to get more oil flow you have more pressure. pumps are sized to have enough idle oil pressure and the bypass circuit sets maximum oil pressure as pump volume goes up due to engine speed increases. if you take a pump with a 50 lb spring that pops off at 2500 rpm and then install a 60 lb spring the engine speed has to be increased to say 3000 rpm to open. the pressure and therefore the volume has to increase to make this happen and the only way this happens is to turn the pump faster.
another example: .you put a high volume pump on your sbc in place of the std volume pump. both have the same 50 lb spring . the hgh volume pump has 40 psi at 1000 rpm and the bypass opens at 2000rpm. the std volume pump has 25 psi at 1000 rpm and the bypass opens at 3k. this engine requires x amount of oil flow to reach 50 psi when factoring the internal leakage and oil viscosity .in my example the std volume pump just reaches this output at 3k. since the flow and pressure requirements are the exact same to get 50 psi regardless of what pump is used the higher volume pump bypasses the additional volume to the pan.
in short the ops engine doesnt need a high volume pump. 25lbs or so hot in gear at idle is plenty of pressure with an adequate amount for safety and a all a hv pump does is cost hp and heat the oil

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Re: Excessive oil pressure

Post by Kevin Johnson » Sat Sep 22, 2018 3:43 pm

A SBC has an internal pressure bypass so that excess oil is returned to the inlet rather than being ejected to the pan. One advantage of having a larger volume than stock is that as the oil is recycled any air bubbles are pulverized and reduced in diameter making their dissolution more felicitous. Dissolved air in the oil allows the oil to still act as an ideal fluid in maintaining the hydrodynamic wedge in the bearings. Yes, the repeated recycling of oil does heat it.

To the extent that you have excellent oil control in the pan, meaning less air entrainment, the above becomes less important. I suspect factory engineers worry about people practicing bootleg turns within the warranty period for crate engines.
All GM Performance engines include a 24 Month 50,000 mile warranty...

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Re: Excessive oil pressure

Post by gnicholson » Sat Sep 22, 2018 4:36 pm

yes stock pumps bypass oil to the inlet.wasnt thinking when i wrote that

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Re: Excessive oil pressure

Post by Ed Wright » Sat Sep 22, 2018 5:45 pm

I don't know of any competitive NHRA race engine builders using high volume oil pumps in Stock Eliminator or Super Stock small block Chevys. Many (I'm not a Pro, I have just built my own since 1966) use spacers & shortened gears to lower volume, worth about five hp. Myself, and many others, have a test plate (mine is just a rear main cap with a gauge) for testing & setting relief spring pressure. Even with a lower volume pump, my 350" is at the pressure I set the spring (50) for by 2000 RPM, warmed up, with 5W20 oil. What could be the point of a high volume pump? I drop it in my parts washer, with my 1/2" drill on the shaft. What I see there, I see in the car.
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Re: Excessive oil pressure

Post by Kevin Johnson » Sat Sep 22, 2018 6:05 pm

There is a difference for an engine that has to survive 1/4 mile at a time versus thousands of miles reliably. I spoke with a customer a short while ago about racers with high dollar sponsors calculating how little oil to leave in the pan so that the engine was dry by the end of the run. The sponsor would pay for a new motor.



Here is a perfectly designed race car ala the philosophy of Colin Chapman:

https://www.youtube.com/watch?v=QfN1GRqKXpM

:lol:
Last edited by Kevin Johnson on Sat Sep 22, 2018 6:15 pm, edited 1 time in total.

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Re: Excessive oil pressure

Post by exhaustgases » Sat Sep 22, 2018 6:11 pm

Kevin Johnson wrote:
Sat Sep 22, 2018 6:05 pm
There is a difference for an engine that has to survive 1/4 mile at a time versus thousands of miles reliably. I spoke with a customer a short while ago about racers with high dollar sponsors calculating how little oil to leave in the pan so that the engine was dry by the end of the run. The sponsor would pay for a new motor.
And why I think the OP made a good choice going with 10W-30 and not lighter viscosity. IMO

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Re: Excessive oil pressure

Post by Ed Wright » Sat Sep 22, 2018 6:20 pm

Kevin Johnson wrote:
Sat Sep 22, 2018 6:05 pm
There is a difference for an engine that has to survive 1/4 mile at a time versus thousands of miles reliably. I spoke with a customer a short while ago about racers with high dollar sponsors calculating how little oil to leave in the pan so that the engine was dry by the end of the run. The sponsor would pay for a new motor.



Here is a perfectly designed race car ala the philosophy of Colin Chapman:

https://www.youtube.com/watch?v=QfN1GRqKXpM

:lol:
I don't know anybody doing that either. If the pump is bypassing oil above an idle, what is more volume going to help?
http://www.fastchip.com/
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Re: Excessive oil pressure

Post by gnicholson » Sat Sep 22, 2018 6:29 pm

thats exactly right. as long as you have enough idle pressure you will have more than enough volume at higher engine speeds to set thr bypass pressure to 70 lbs or whatever you want

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Re: Excessive oil pressure

Post by wilson1970 » Sat Sep 22, 2018 6:40 pm

I went to local engine builder years ago and this is what he sold me right or wrong trusted his knowledge. Looking back I should have bought a typical z28 pump and been done. Thanks to the few that have been helpful with suggestions.

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Re: Excessive oil pressure

Post by gnicholson » Sat Sep 22, 2018 7:04 pm

the way i see it you had 3 choices. the easiest and one you chose was to put lighter oil in it. probably what i would have done as well. the 2nd was to remove and modify the exosting pump by adding pressure balance grooves or some other mod to increase leakage or in my opinion the best option which would be the z28 pump. what oil pressure do you have at higher rpm hot?

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Re: Excessive oil pressure

Post by Kevin Johnson » Sat Sep 22, 2018 8:27 pm

Ed Wright wrote:
Sat Sep 22, 2018 6:20 pm
Kevin Johnson wrote:
Sat Sep 22, 2018 6:05 pm
... I spoke with a customer a short while ago about racers with high dollar sponsors calculating how little oil to leave in the pan so that the engine was dry by the end of the run. The sponsor would pay for a new motor.

...
I don't know anybody doing that either. If the pump is bypassing oil above an idle, what is more volume going to help?
I have talked with a lot of people about oiling systems for hundreds of different types of engines -- I do not think this specifically was discussed on SpeedTalk. Back in the 1960s in the NHRA Stock division it would have been illegal to modify the OEM pumps. I think running an accumulator would fall under the same aegis. Calculating the minimum amount of oil needed to run the engine would be an exercise more common prior to the widespread use of accumulators. I don't think this would be something they would broadcast to their competitors.
1966_NHRA_Stock_engine_rules.png
Later on, NHRA rules specifically call out what can be done with oil pumps. I guess it would somehow fall under "OEM aftermarket replacement oil pump." :lol: :wink:
2017_NHRA_Super_Stock_engine_rules.gif
Yes, I am sure the original poster would have also been happy with a Z28 pump but the HV pump also seems to have served him well over the years.

Have racers calculated the potential timing improvement using gear drive pumps with more teeth (maybe like the BBC)? Mercedes published data on this back in the mid 1970s. Surely you could shorten those gears as well? :wink:
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