Hi guys I have bb chev engine and would like to know if anybody is using a high volume oil pump with a standard 5 qt 0il pan my pressure starts out at 40 psi then drops down to 20 psi when engine warm up. I have a engine oil cooler and the chev manual said that if you are using a oil cooler you should install a 1/8 spacer behind the relief valve spring . would a high volume work also
ken5537
To change the oil pressure you change the spring that keeps the over pressure by pass valve closed. Putting a spacer behind it pre loads the spring but doesn't change the spring rate (so you start out at higher pressure but it will fall off at the same rate as before).
Melling High-Pressure Oil Pump Springs 77070 (pink 70 psi)
https://www.summitracing.com/parts/mel-77070
or the Green 78 psi spring:
https://www.summitracing.com/parts/mel-55078?rrec=true
and here is the yellow 85-90 psi spring:
https://www.summitracing.com/parts/sum-122171?rrec=true
A high volume pump was used by used car lots to make a clapped out used car with over a hundred thousand miles on the odometer have decent oil flow through the engine to prevent the rods from knocking. When an engine is new, the clearances are tight and the pressure is good. As the bearings and lifter bores wear, clearances increase, resistance to flow decreases, and oil pressure starts to drop.
Today used car lots are prevented from turning back the odometer or doing things like installing a high volume pump (which is how I kept my shop doors open rebuilding motors on the cheap for used car lots after the law was passed). Another trick they pulled was to pour Comet through the carb to get a very, very, short term ring seal to prevent a smoker from looking like a mosquito control truck at the auction. A hundred miles later that engine stopped running due to ring failure.
In racing you use a high volume pump to compensate for the massive internal oil leak created by using a crank with a generous fillet (makes the crank stronger not to have a ninety degred corner for the rod bearing) but the chamfered bearings required only covered two thirds of the rod journal (cuts down on friction, but there is nothing to hold the oil in place so it squirts out). That is why they make and sell high volume oil pumps.
A high volume pump takes thirty percent more energy to drive the pump, which accelerates the wear on the distributor gear. This is an issue in a race engine using a brass distributor gear as they can wear out on four thousand to ten thousand miles. I used to use plastic gears made in Germany back when I was still using a billet steel core custom ground cam, to get more wear out of the gear for better timing control.
Big Dave
Melling High-Pressure Oil Pump Springs 77070 (pink 70 psi)
https://www.summitracing.com/parts/mel-77070
or the Green 78 psi spring:
https://www.summitracing.com/parts/mel-55078?rrec=true
and here is the yellow 85-90 psi spring:
https://www.summitracing.com/parts/sum-122171?rrec=true
A high volume pump was used by used car lots to make a clapped out used car with over a hundred thousand miles on the odometer have decent oil flow through the engine to prevent the rods from knocking. When an engine is new, the clearances are tight and the pressure is good. As the bearings and lifter bores wear, clearances increase, resistance to flow decreases, and oil pressure starts to drop.
Today used car lots are prevented from turning back the odometer or doing things like installing a high volume pump (which is how I kept my shop doors open rebuilding motors on the cheap for used car lots after the law was passed). Another trick they pulled was to pour Comet through the carb to get a very, very, short term ring seal to prevent a smoker from looking like a mosquito control truck at the auction. A hundred miles later that engine stopped running due to ring failure.
In racing you use a high volume pump to compensate for the massive internal oil leak created by using a crank with a generous fillet (makes the crank stronger not to have a ninety degred corner for the rod bearing) but the chamfered bearings required only covered two thirds of the rod journal (cuts down on friction, but there is nothing to hold the oil in place so it squirts out). That is why they make and sell high volume oil pumps.
A high volume pump takes thirty percent more energy to drive the pump, which accelerates the wear on the distributor gear. This is an issue in a race engine using a brass distributor gear as they can wear out on four thousand to ten thousand miles. I used to use plastic gears made in Germany back when I was still using a billet steel core custom ground cam, to get more wear out of the gear for better timing control.
Big Dave
Interesting stories, Dave. Thanks for sharing. So, are you saying you standard street car should be running a standard volume and pressure pump?
OP
"high volume" pumps in motors that are not built with slightly wider bearing clearances should not be used. You can put in a "higher pressure" spring in your stock pump with stock bearing clearances
"high volume" pumps in motors that are not built with slightly wider bearing clearances should not be used. You can put in a "higher pressure" spring in your stock pump with stock bearing clearances
On a stock motor or nearly stock motor I would run a standard pump.
There are lots of schools of thought on the oil pump subject, lots and lots of opinions and data. I researched it quite a bit when I built my last motor since it's very unique, and what I found was the consensus of engine builders was almost never does a SBC or BBC need higher pressure, but higher volume is recommended in cases.
I have heard the opposite of what Dave describes above, people use high pressure to increase total pressure on a loose motor. High volume moves more oil so idle pressure may increase but the peak pressure doesn't (which is based on the spring in the pump). I believe my pump used a 3/4" pick up as opposed to the standard 5/8 also.
I don't know though, like I said you could read for months on the subject. I found that generally stock is plenty, Chevy oiling systems are pretty well designed. And the Dart blocks are an improvement on that.
My motor I ended up using a standard pressure higher volume pump, I believe 10% more volume. Based on slightly looser clearances and high RPM use.
There are lots of schools of thought on the oil pump subject, lots and lots of opinions and data. I researched it quite a bit when I built my last motor since it's very unique, and what I found was the consensus of engine builders was almost never does a SBC or BBC need higher pressure, but higher volume is recommended in cases.
I have heard the opposite of what Dave describes above, people use high pressure to increase total pressure on a loose motor. High volume moves more oil so idle pressure may increase but the peak pressure doesn't (which is based on the spring in the pump). I believe my pump used a 3/4" pick up as opposed to the standard 5/8 also.
I don't know though, like I said you could read for months on the subject. I found that generally stock is plenty, Chevy oiling systems are pretty well designed. And the Dart blocks are an improvement on that.
My motor I ended up using a standard pressure higher volume pump, I believe 10% more volume. Based on slightly looser clearances and high RPM use.
There is nothing wrong with a high volume pump if you have a larger oil pan and plan on (or are) running an external oil cooler or remote oil filter(s).
Not sure on the 30% number, I know high pressure pumps pumps rob HP, not so much with HV pumps. Wear isn't an issue, at least on my engine with HV pumps.
OP: how many miles on the motor? Is the pressure number you mention at idle? What weight oil?
Not sure on the 30% number, I know high pressure pumps pumps rob HP, not so much with HV pumps. Wear isn't an issue, at least on my engine with HV pumps.
OP: how many miles on the motor? Is the pressure number you mention at idle? What weight oil?
Pascal's law applies only to incompressible fluids like motor oil.
Which explains how you can force a fluid up hill under pressure (it is how all hydraulic actuators like cylinders on construction equipment or your car's hydraulic brakes work.
I think you were thinking in terms of The Ideal Gas Law. The Ideal Gas Law cannot be applied to liquids. The Ideal Gas Law is stated as PV=nRT . That implies that V is a variable. But a liquid has a constant volume (unlike a gas which can be compressed into a smaller volume, so the Ideal Gas Law cannot apply to a liquid.
An oil pump as used in a Chevy engine is a positive displacement pump. What goes in one side has to come out the other. Because it is a positive displacement pump if you have any kind of restriction on the out put side the pressure before the restriction will increase. Restrictions can be small holes drilled in cast iron that offer fluid friction to oil or any fluid attempting to got through the hole. Smaller the hole (oil) the higher the pressure will build. The longer the (deeper if you prefer) the hole the higher the friction and the higher the pressure will be.
A positive displacement gear oil pump moves a fixed volume of fluid per rotation. To get motor oil you increase either the diameter of the gears (such as going from a SBC to a BBC oil pump, or you make those gears longer so that the face of the gear sees more oil on each rotation. The pressure is fixed by fluid friction and the strength of the material being used. You can exceed several thousand psi with a gear pump if it is obstructed. To keep from splitting the block apart (as happens in the Olds 401 engine and the Ford small block 289-302 you have to limit the pressure with a bypass valve.
You use a nice linear force to control the pressure which is determined by Hooke's law. Suffice to say the stiffer the spring rate the more force it can apply (all things being equal).
The BBC oil pump has a 3/4 inch tube diameter for it's pick-up. The SBC has a 5/8th inch inlet tube size. A BBC pump will bolt up to a SBC main cap but it requires a custom length drive shaft from the distributor (if anyone wants to really go overboard on oil volume for your SBC.
Big Dave
Which explains how you can force a fluid up hill under pressure (it is how all hydraulic actuators like cylinders on construction equipment or your car's hydraulic brakes work.
I think you were thinking in terms of The Ideal Gas Law. The Ideal Gas Law cannot be applied to liquids. The Ideal Gas Law is stated as PV=nRT . That implies that V is a variable. But a liquid has a constant volume (unlike a gas which can be compressed into a smaller volume, so the Ideal Gas Law cannot apply to a liquid.
An oil pump as used in a Chevy engine is a positive displacement pump. What goes in one side has to come out the other. Because it is a positive displacement pump if you have any kind of restriction on the out put side the pressure before the restriction will increase. Restrictions can be small holes drilled in cast iron that offer fluid friction to oil or any fluid attempting to got through the hole. Smaller the hole (oil) the higher the pressure will build. The longer the (deeper if you prefer) the hole the higher the friction and the higher the pressure will be.
A positive displacement gear oil pump moves a fixed volume of fluid per rotation. To get motor oil you increase either the diameter of the gears (such as going from a SBC to a BBC oil pump, or you make those gears longer so that the face of the gear sees more oil on each rotation. The pressure is fixed by fluid friction and the strength of the material being used. You can exceed several thousand psi with a gear pump if it is obstructed. To keep from splitting the block apart (as happens in the Olds 401 engine and the Ford small block 289-302 you have to limit the pressure with a bypass valve.
You use a nice linear force to control the pressure which is determined by Hooke's law. Suffice to say the stiffer the spring rate the more force it can apply (all things being equal).
The BBC oil pump has a 3/4 inch tube diameter for it's pick-up. The SBC has a 5/8th inch inlet tube size. A BBC pump will bolt up to a SBC main cap but it requires a custom length drive shaft from the distributor (if anyone wants to really go overboard on oil volume for your SBC.
Big Dave
Nice write up Big. I had an issue on a wastewater treatment plant with a Positive displacement sludge pump. The engineer insisted on a $25K variable valve on the pump discharge "To keep it on the pump curve". Kept blowing rupture discs. Did not understand that the PD Pump doesn't really care until you CLOSE A VALVE ON THE DISCHARGE. Boom-Rupture Disc. Disabled the automatic valve and no further problems
Curious as to how the FT lifters with the edm holes fit into this? This introduces an additional “bearing clearance” or calculated leakage into the equation. Does this then automatically trigger the need for a high volume pump? Or is this small diameter hole, usually around 0.020 inches, just too small to effect anything even multiplied by 16 lifters. This is equivalent to an extra 0.080 inch diameter hole in the oiling system, although I have read that it isn’t exactly so as it is against the flat face of the cam lobe so it is partially obstructed. Thoughts?
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Sent from my iPhone using Tapatalk
Used car dealers can't do it. You can.
It is considered fraud to pass off a known problem to a customer under a variety of local state and federal laws. Consumer Protection Act is a federal law Trump is trying to get rid of because it hurts business, but it keeps a used car business from hurting you.
This doesn't mean when they were rebuilding engines to resell an otherwise sellable body they were going for a rebuild you would accept. Dingle berry hone with cheap cast iron rings, and 0.002" over sized bearings were the extend of their rebuild effort. They were more concerned with paint job on the motor (no fresh paint) than the quality of the build. I used to buy scrap iron destined to go to a Toyota plant from the east coast and mid west shipped out of Tampa. I went down once a week with a crane on my one ton truck and loaded up with seven SBC motors (or Fords or Chryslers* if needed) and took them back to my shop. Blew them apart to find the good reuseable parts and got two to three motors a week that I could sell out of the scrap pile. Took the rest back to the scrap yard weighed in took out seven more paying only the difference in scrap metal prices.
Lot of the engines I installed in those old cars got steel cranks and fuelie heads that way so they were better than the factory engine.
* I never saw a 318 Polysphere engine or a slant six from Crysler in the scrap pile. They must have been indestructible.
Big Dave
It is considered fraud to pass off a known problem to a customer under a variety of local state and federal laws. Consumer Protection Act is a federal law Trump is trying to get rid of because it hurts business, but it keeps a used car business from hurting you.
This doesn't mean when they were rebuilding engines to resell an otherwise sellable body they were going for a rebuild you would accept. Dingle berry hone with cheap cast iron rings, and 0.002" over sized bearings were the extend of their rebuild effort. They were more concerned with paint job on the motor (no fresh paint) than the quality of the build. I used to buy scrap iron destined to go to a Toyota plant from the east coast and mid west shipped out of Tampa. I went down once a week with a crane on my one ton truck and loaded up with seven SBC motors (or Fords or Chryslers* if needed) and took them back to my shop. Blew them apart to find the good reuseable parts and got two to three motors a week that I could sell out of the scrap pile. Took the rest back to the scrap yard weighed in took out seven more paying only the difference in scrap metal prices.
Lot of the engines I installed in those old cars got steel cranks and fuelie heads that way so they were better than the factory engine.
* I never saw a 318 Polysphere engine or a slant six from Crysler in the scrap pile. They must have been indestructible.
Big Dave
Well ken heres my two cents worth. What is the engine in that it has an oil cooler a pick up and how many miles plus engine condition. Two unless its a purpose built engine with extra clearances there is no need for a high volume pump. The g/m engineers knew what they were doing when they designed the oiling systems for the sbc and bbc. It is ok to use a heavier spring like the pink z-28 in or the blue bbc spring which raises the pressure. An h v pump increases the volume by 25% and is harder to drive plus you also have to increase the pan capacity to fit the need. I have been around the block a few times and have seen many a used car cure all . Laquer thinner in the hydramatic brake fluid to swell seals etc . Water down the carb for cleaning the carbon out . Old nailhead buicks were notorious for carbon knocks. Ham burger in the rear end .we once rebuilt a 430 lincoln engine for a customer who insisted on chrome rings. We told him they wont seat and you,ll wind up with an oil burner . Well he insisted so hastings chrome rings it got . Six weeks later he came back complaining of oil cosumption and wanted the engine redone at our expense mind you it ran fine but used oil . In order to avoid problems m,y uncle said can you leave it for a few days so we can take care of the problem . The man was happy and left i said to my uncle your not doing this whole thing over again . His answer to me was go down to the first national and get me a can of babbo or comet. I said ok what for he said just go get it. When i came back i asked what are you gonna do. He said were gonna seat the rings down the carb went the babbo treatment. I asked whats that going to do he said it has pumice in it and will seat those hard chrome rings. I was shocked it did work. The rest of the time was spent driving it to get the oil out of the exhaust system. Use the std pump with the high pressure spring and if you do not need the oil cooler eliminate it if it can be done easy enough. Through the years we have eliminater a few coolers for different reasons without problem . There are those who will say you cant do that its not right and will ruin the engine . You can we have and had no problems . Here again i will say there are some than you can and then there are tose that need the cooler and you must not remove it .. Alex
Hi the answer to your question . the engine is a yenco 427 engine it uses a oil cooler the oil goes out from the side of the block thru the oil cooler and then back to the filter . the oil is then filtered and then the oil goes into the block for lubrication. thanks for all the info you guys are saying about oil pumps and applications It looks like I should use the green spring and just use the standard melling oil pump thanks for all the info great job ken
Thanks for the respectful reply. I am no lawyer (though in Florida we are up to our keister in them) so back in the day they had the used car lots running scared. Since I benefited from the work I couldn't complain, nor would it be profitable for me to have done so. That is what most of the dealers selling used cars thought that I worked with believed at the time.
Big Dave
Big Dave
Lots of posts here but little to help the guy out with low idle oil pressure....
The reason it has 40psi cold but 20 hot is because the oil thins out & the pump does not produce enough volume at idle.
It does not matter what spring is in the pump (it could be 45 or even 150psi rated) if it only has 20psi at idle, the relief spring is not allowing the bypass to open. You need tighter bearing clearances, thicker oil or a higher volume pump to get more pressure at idle.
The spring is for the max oil pressure setting. What is is above 4000rpm? This is where the spring may help assuming the pump has enough volume to do so.
First, is 20psi too low.... probably not, it just looks bad. What is it above idle, is it 30-40 at 1500-2000 rpm?
The suggestion is 10psi per 1000rpm at WOT.
What oil are you running? Jumping up to 10w40 over 10w30 will increase your hot oil pressure a bit.
A high volume pump should not suck a factory BBC pan dry. I have a factory pan, hand fitted crank scraper & a high volume pump. I shift it at 7200 & it holds over 60psi. I'm runnig 20w50 oil with 40psi at a 1200rpm idle. You do have to be careful not to rev a cold engine as it will easily go over 80psi.
Give some deatils on pressure at various rpm's & the oil you are running & then it can be determined if you should run a larger pump.
The reason it has 40psi cold but 20 hot is because the oil thins out & the pump does not produce enough volume at idle.
It does not matter what spring is in the pump (it could be 45 or even 150psi rated) if it only has 20psi at idle, the relief spring is not allowing the bypass to open. You need tighter bearing clearances, thicker oil or a higher volume pump to get more pressure at idle.
The spring is for the max oil pressure setting. What is is above 4000rpm? This is where the spring may help assuming the pump has enough volume to do so.
First, is 20psi too low.... probably not, it just looks bad. What is it above idle, is it 30-40 at 1500-2000 rpm?
The suggestion is 10psi per 1000rpm at WOT.
What oil are you running? Jumping up to 10w40 over 10w30 will increase your hot oil pressure a bit.
A high volume pump should not suck a factory BBC pan dry. I have a factory pan, hand fitted crank scraper & a high volume pump. I shift it at 7200 & it holds over 60psi. I'm runnig 20w50 oil with 40psi at a 1200rpm idle. You do have to be careful not to rev a cold engine as it will easily go over 80psi.
Give some deatils on pressure at various rpm's & the oil you are running & then it can be determined if you should run a larger pump.
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