High volume vs. high pressure oil pump

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hemichuck

hemichuck

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an old friend of mine who used to build super stock hemis always told me to us eight volume oil pumps as opposed to high pressure pumps, since I had so much respect for his abilities to build a motor I never bothered to ask him why. He passed away years ago and I always took his advice( which I guess was good since I never blew up any of my motors) so now I was wondering if someone could explain his logic.
 
must be a full moon again

(no offence Chuck, little inside joke...this question comes up about once a month like clockwork and it is like asking Ginger or Mary-Anne)
 
A high volume pumps more oil than stock and a high pressure pumps at a higher pressure than stock. A stock pump is probably adequate for over 90% of street driven builds. That's the shortest and best explanation.
 
It´s all about the clearances inside the engine. If an engine has tight clearance, then the stock volume oil pump is sufficient to produce enough pressure. If an engine has got loose clearance, then sometimes the high volume pump is necessary to produce enough pressure. If you put a high volume pump into an engine with tight clearance, you may end up with high oil pressure up to the point of where the relief valve opens.....and some of the oil flows under pressure directly back to the sump (lost power).

In my opinion, in most cases, if an engine is built right, a stock volume pump is sufficient. If you have some kind of valve spring spray bars or other "leakage points" like lifters with oil holes to lube the cam directly, then a high volume pump could be beneficial.

Michael
 
Maybe I should have searched before I asked! I know why he used high volume, I was more or less wondering why he was against a high pressure pump and what were the circumstances that would require high pressure? I remember the first time we had this conversation was when I had put my 426 Hemi into a 1966 Belvedere 4 door to street race and after it warmed up the oil pressure gauge at an idle would drop below 10 pounds. Kind of freaked me out because after all I had paid $600 for that Hemi ( kind of like spending $20,000 in today's dollars) and thought maybe I had got screwed when I bought it. Of course the common sense answer was it needs more pressure so when I went to the parts store they ask HV or HP? And I said HP. After he saw what I bought he told me two things I have always lived by, never use a high pressure oil pump and never use Valvoline motor oil, and I never have. So I'm guessing the high pressure pump would only get used on something really loose like those old qualifying motors that Harry Hyde used to use in NASCAR. The reason the question came now is because I just got a 4 inch stroke Magnum motor and it came with a mellings HP pump.
 
Like mentioned,,,it's all about clearances. High volume will equal high pressure with tight clearances. It's impossible not too.
I'm not even sure if anyone sells a pump that's "high pressure". Pumps are based on volume,,,and what you pump through will dictate pressure.
On my stroker I run a high volume. I've done oiling mods to reduce restrictions in the block, and added bypasses to oil the valve train earlier, so now I can pump more oil through faster.
 
HV: The high volume pump has 20% taller rotors and will pump about 18-20% more volume at a given pressure.
HP: A higher pressure spring in the relief valve will make ANY pump a 'high pressure' pump. There are 2 common springs in the SBM pumps, one at around 55 PSI, and the other at 72 PSI. You can have either spring in either the standard volume or HV pump.

The high volume pump is useful in a way that most people don't think about: it will keep higher pressure into the engine at low RPM's and idle. The SBM high volume is not all THAT high a volume compared to other engines' so-called hi-volume pumps so going to the SBM HV pump is not as big a deal as some people make it out to be.

JIMHO......The power losses in any pump may a consideration for getting the maximum HP out at peak HP at many thousands of RPM's. But pumping loss is low at regular street RPM's so the added pumping loss of a HV pump is trivial most of the time. IMHO, I would rather use a HV pump that will maintain better pressure at low RPM's (where I operate 99% of the time) and lose 0.5 HP cruising down the road. Keep in mind that the pressures drop and drop as the oil moves through the system, so 10 to 20 psi drop at idle at the guage, which is right after the filter, with a smaller pump will lead to less oil at the rockers and the left lifter bank, which are way down at the 'end of the line' for oil distribution. An HV pump helps this at low RPM's.

And post #6 has one minor error.... when the pressure relief valve opens in the SBM pumps, the some of the output oil recirculates inside the pump. It does not get diverted back to the pan.
 
Ok,,,I see now what they mean by high pressure pump,,it's regarding the bypass. Cool, learn something new everyday :)
 
I use HV\HP pumps in all my stuff. There is no reason to have idle oil pressure under 30 pounds, especially if you are running nonstock parts.

BTW, who determines high volume and standard volume?

Look at a dry sump pump. They are all HIGH VOLUME compared to stock junk.

The more oil the pump puts out, the quicker the system has pressure. At slower pump speeds, the HV keeps oil at the rockers. If you think 90 pounds of spring pressure is a lot, then you can use a standard pump.
 
High pressure oil pumps put more heat in the oil, you don't want that unless it's a reasonable or worthwhile trade off for oiling needed high rpm and or major oiling system mods clearances . Fact -anytime you try n compress oil trying to force it through a pee hole...you make more heat and eat up HP. Revisiting a jk made in another thread.lol
High volume will suit a loosely clearanced motor under 7500 rpm or one with opened up/modified oil gallies and closer to stock clearances. Whatever combo of loose or tight or modified...you compensate accordingly.
Note that as long as you have 7-8 psi per 1000 rpm, it will live.
 
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MOPAROFFICIAL said:
High pressure oil pumps put more heat in the oil, you don't want that unless it's a reasonable or worthwhile trade off for oiling needed high rpm and or major oiling system mods clearances . Fact -anytime you compress a fluid you make heat.
High volume will suit a loosely clearanced motor under 7500 rpm or one with opened up/modified oil gallies and closer to stock clearances. Whatever combo of loose or tight or modified...you compensate accordingly.
Note that as long as you have 7-8 psi per 1000 rpm, it will live.
Click to expand...

Fact - fluids aren't compressible. But I get what you're saying :p
 
I went out and took a photo of the pump and it does in fact say M72HP which is not even listed in the Mellings catalog anymore.
 
hemichuck said:
I went out and took a photo of the pump and it does in fact say M72HP which is not even listed in the Mellings catalog anymore.
Click to expand...

That's definitely a Mellings... :p

All Mellings have 72 psi springs whether HV or std.... :D

Not that there's anything wrong with that.... :rolleyes:
 
There was a service bulletin on 66 Hemis with oil light flickering at idle, loose clearances even when new. Not to worry.
 
MOPAROFFICIAL said:
High pressure oil pumps put more heat in the oil, you don't want that unless it's a reasonable or worthwhile trade off for oiling needed high rpm and or major oiling system mods clearances .
Note that as long as you have 7-8 psi per 1000 rpm, it will live.
Click to expand...
Compared to the heat that the oil gets from the pistons and cylinder walls, any pump heating in this case is nothing in these pump sizes, so to not run modestly higher pressure to avoid a trivial amount of oil heating is a poor tradeoff IMHO. We are only talking the difference between 55 psi and a 72 psi spring in a SBM pump.

And 7-8 psi at the gauge port means roughly 0-2 psi feeding the rocker to shaft interface. For stock rockers and springs where there is really no oil pressure at the rocker to shaft interface, all you need is a bit of flow and splash. For fancier rockers and high pressure springs, then you are wise/need to have better and better pressure to keep positive oil flow through the rocker system and keep positive oiling pressure to the pushrod cups, rollers, etc. Depending on the setup , there are around 5-7 restrictions between the lifter gallery and the rocker-to-shaft interface, plus the 'interruptor' action in the cam, that cuts pressure way down to the LA rockers.
 
There is not pressure at the rockers. It's by design splash fed. If you think otherwise look close at the stamped rockers, how much they move, and the design of the groove.
High pressure is in regard to the relief spring choice. High volume is in regard to the fluid output via a he rotor size. The pressures indicated on the gage are a function of the oil, the pump, and the clearances. So the choice in pump needs to be made by the guy designing the package.
 
moper said:
There is not pressure at the rockers. It's by design splash fed. If you think otherwise look close at the stamped rockers, how much they move, and the design of the groove.
High pressure is in regard to the relief spring choice. High volume is in regard to the fluid output via a he rotor size. The pressures indicated on the gage are a function of the oil, the pump, and the clearances. So the choice in pump needs to be made by the guy designing the package.
Click to expand...


Until you go to adjustable rockers.

There is always pressure up there.
 
MaryAnne would be helping figure out the pressure problem, or providing a healthy lunch for those doing so.
Ginger would be moving the mirrors askew to touch up face paint and keep asking if dinner at $$+ was going to be on time.

Hi-volume pumps for me.
Hi- pressure puts that look on Ginger's face.
 
nm9stheham said:
Compared to the heat that the oil gets from the pistons and cylinder walls, any pump heating in this case is nothing in these pump sizes, so to not run modestly higher pressure to avoid a trivial amount of oil heating is a poor tradeoff IMHO. We are only talking the difference between 55 psi and a 72 psi spring in a SBM pump.

And 7-8 psi at the gauge port means roughly 0-2 psi feeding the rocker to shaft interface. For stock rockers and springs where there is really no oil pressure at the rocker to shaft interface, all you need is a bit of flow and splash. For fancier rockers and high pressure springs, then you are wise/need to have better and better pressure to keep positive oil flow through the rocker system and keep positive oiling pressure to the pushrod cups, rollers, etc. Depending on the setup , there are around 5-7 restrictions between the lifter gallery and the rocker-to-shaft interface, plus the 'interruptor' action in the cam, that cuts pressure way down to the LA rockers.
Click to expand...
Why you post rebuttal to my post i have no idea why other than you missed the entire point i was making about high pressure pumps, which is ...unless you need to turn huge rpms and or have a modified oil system that necessitates such pump....all you will be doing is eating up HORSEPOWER trying to compress a fluid and putting MORE HEAT into the oil.
55 and 72 psi....What pumps are attaching these ratings to? Melling oil pumps out around that 72 number till things warm up and expand...then its 65psi. 55 sounds like a factory magnum which never see's higher than 4200 rpm, plenty of oil for that tame motor..
 
This pump came with a 408 Magnum motor with a Hughes hydraulic roller cam and it has harland sharp roller rockers. Probably never go over 6000 except very briefly.
 
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