High volume against High pressure oil pump

[Nacho-RT74]

Advantages of one over the other ?
when is better use one or another ?

I found a nice price M-63HP Melling oil pump ( just $55 ) what is cheap being already located down here and I decided to buy since is being really harder to find any kind of oil pump, including stock, but wanted to know why or when is better one over the other.

[RogerDodger]

I was told to use a high volume pump and not high pressure pump when freshening up my 318. The increased volume makes up for worn tolerances. Someone correct me if i'm wrong.

[Nacho-RT74]

ok, some other opinion or advise ?

[RogerDodger]

here is something I found on a google search that might help.

http://www.aa1car.com/library/2005/us020516.htm

http://books.google.com/books?id=TXEMMgByjfIC&pg=RA1-PA74&lpg=RA1-PA74&dq=high+volume+oil+pump&source=web&ots=O7piAyoANa&sig=NowgXp_REfBkRV0WJz1anXS7TVQ#PRA1-PA73,M1

I was going to order a high volume pump today. Now I'm confused after doing a little research. Some say high volume isn't necessary and robs horsepower. I hope someone chimes in that can shed a little light.

[Nacho-RT74]

I have found on summit catalog ( on line and book ) that is most common to find HV instead HP oil pumps.

will check the links

[Chatt69chgr]

I read that link Rogerdodger supplied and it looks to me that if you have rebuilt your engine and have the bearing clearances down to spec that you would not need a high volume oil pump.  I'll be rebuilding my engine and will want to purchase a new oil pump.  Many, many years ago when I rebuilt an engine, we didn't give much thought to oil pumps.  We just went down and bought a Melling and that was that.  I hope that might still be the case.  I did note the info about replacing the pickup tube and input screen due to not being able to get all the debris out.  That's some good info.  I'll be following the thread to see what the site experts advise so I can apply the info to my rebuild.  Good post Nacho.

[is_it_EVER_done?]

A couple of points: First, there is really no such thing as a "High Pressure" pump, as any HP pump will either be a stock pump or High Volume pump, but with the stock pressure release spring replaced with a stiffer unit. So simply buying a HP spring "black in color" will turn any pump into a HP pump. There are also available adjustable pressure kits that allow you to adjust the spring tension by turning a nut or screw.

As far as HV pumps, they are deeper than a stock pump (longer rotors) so that they have the POTENTIAL to pump more oil. Keep in mind that potential is NOT the same as actually doing so as bearing clearances dictate how much oil can flow through the engine. The only way to increase this flow is to boost the pressure. A HV pump cannot pump "more" oil than a stock pump at the same pressure.

Do you need a HV pump in a non high RPM (race) build? Absolutely not as long as you have adequate oil pressure at max RPM (50 pounds or more), and the stock pump is much more than adequate to supply ample oil at RPM's of 6000 or even more, in a normal build. If you are going with large bearing clearances, a HV pump may be beneficial, but unless you are upgrading the pick up (and it's related oil passages) to 1/2 inch, an HV can't pass more oil than a stocker.

The downsides to an HV pump are: It will take a bit more power to turn as it's "trying" to pass more oil so it must also "bypass" more oil.

Because it takes more power to turn, you MUST upgrade to a hardend oil pump drive shaft (not a bad idea even on a stock rebuild also). The stock pump drive shaft is weak, but is adequate for stock to mild performance builds, but they can break off if you start pushing their design limitations, and zero oil pressure is undesirable no mater which pump you use.

It's physically deeper/longer than stock so you will need to get new bolts to hold it on the block as the stockers just barely engage a few threads and leaks/thread stripping is not uncommon.

Just for information, no serious racers use the HV pump, as the stocker has proven more than adequate and consumes a bit less power. Some "port" the pump, meaning that they round off the square edges of the ports and oil pickup tube galleys, but the volume of a stock pump is designed to be more than is necessary if the pick up tube is large enough.

Now to bust a myth: on any given engine, a HV pump can not/does not draw more oil out of the pan, so it can't "suck the pan dry". Either pump simply "bypasses" the extra oil that it cannot pump and returns it back to the pump rotors/cavity which is the same as returning it to the pan. Even if you had an engine that had monstrous bearing clearances, the oil volume returned to the pan is exactly the same as is being drawn, since the oil is not "consumed", only circulated.

If you want to use the HV pump, and are willing to upgrade to a hardend pump drive shaft, and longer attaching bolts, it won't hurt anything, and the bit more power that the HV pump uses will NEVER be noticed, or even measureable in time slips, but it's not necessary. With that said, I use an HV on my Charger engine, but only because I have a two quart oil accumulator on it, and think that the additional volume may recharge it faster. I don't know if this is true, but it seems logical.

If you use the HV, just get a hardend pump drive shaft, and longer bolts. --- By the way, ALL stock type pumps for Chryslers are built by Melling, regardless of brand that they are sold under, so shop by price.

[RogerDodger]

Thats some good info. Thanks.

[Chatt69chgr]

I think that Is it ever done has certainly given us the "skinny" on oil pumps.  I am glad to see that I can use the stock piece.  Does Melling make the hardened shaft too?

[firefighter3931]

HV pumps are high pressure by design. Personally, i like them and run them in all my engines. I like slightly looser bearing clearances .0025 and run a 1/2in pickup. Lots of oil pressure is a good thing, within reason. Street driven cars need good idle oil pressure because the camshafts are splash lubed off the crank & rods....not pressure fed. The hardened oil pump drive is a good idea as well. Increasing volume will increase pressure.... that is basic fluid dynamics. 


Ron

[Nacho-RT74]

Increasing volume will increase pressure.... that is basic fluid dynamics. 

Of course that's by default as far you use same ducts size

[Nacho-RT74]

A couple of points: First, there is really no such thing as a "High Pressure" pump, as any HP pump will either be a stock pump or High Volume pump, but with the stock pressure release spring replaced with a stiffer unit. So simply buying a HP spring "black in color" will turn any pump into a HP pump. There are also available adjustable pressure kits that allow you to adjust the spring tension by turning a nut or screw.

In fact, those kits ara availabe on YR1 I think. Of course is not a big deal about buy the HP pump, but in my case since stock pumps are becoming hard to find locally AND very expensive when we find, because dealers KNOW they are becoming hard to find, then they overprice them

[is_it_EVER_done?]

HV pumps are high pressure by design. Personally, i like them and run them in all my engines. I like slightly looser bearing clearances .0025 and run a 1/2in pickup. Lots of oil pressure is a good thing, within reason. Street driven cars need good idle oil pressure because the camshafts are splash lubed off the crank & rods....not pressure fed. The hardened oil pump drive is a good idea as well. Increasing volume will increase pressure.... that is basic fluid dynamics. 
Ron

I really hate to offer a correction but,  a HV pump, unless it has a high pressure spring installed in the pressure relief bypass, can not produce more pressure than a stock pump with the same spring, so HV pumps are absolutely not HP by design.

Lots of oil pressure is only a power robbing (parasitic) loss at any RPM as the amount of oil pressure is totally insignificant as long as the bearings are being supplied an ample amount of oil. The oil's shear strength is the important factor as the minuscule addition to shear strength that "pressure" provides is non existent unless you get into the 1,000's of lbs, of oil pressure.

It is impossible to increase volume without increasing pressure! Oil, like any fluid, is non compressable. The ONLY way to increase volume is to increase pressure so that "more" oil is forced through the oil gallies. If a HV and HP pump have the same "oil pressure relief spring" in them, they will have identical oil pressure! The HV pump will be bypassing more oil than the stock pump will, but all that does is require a bit more power to do over a stock pump.

The only thing a HV pump can do is provide more oil if the stock unit can't due to reaching it's maximum capacity. Fortunately, the Chrysler engineers designed in to the stock pump a large margin of capacity, so that in anything but pro racing, it has more than enough capacity.

Because you run such large bearing clearances, I agree that a HV pump provides extra protection, but I also have to ask WHY you run such large clearances? With modern oils, these huge clearances went out over 25+ years ago! I don't mean to be critical, but can you show ANY benefit to this today? It just doesn't make any sense in any car that can be street driven!

Overall, Is running a HV pump a bad thing? No, but it's one of those things that (in 99% of the "real world" applications) is a total waste. And since it requires more power to turn, it can be a very detrimental thing if the (oil pump") drive shaft hasn't been upgraded to a hardend unit, and since the hardend shaft is twice as expensive as the pump, it's just an additional expense that is not necessary. It certainly can't hurt with the necessary upgrades, but it's useless in all but the most extreme cases, which no one on this web site has need for.

[Nacho-RT74]

eeehmmm... I think I still have to be agreed with Ron, about with more Volume you get also more pressure keeping same ducts and gallies by default, maybe not A BIG DIFFERENCE but still more pressure, enough to not be depreciated... unless there is something I don't understand about oil pum mechanics

However of course that if you drive more volume on same gallies also you need more power to move it

[firefighter3931]

With modern oils, these huge clearances went out over 25+ years ago! I don't mean to be critical, but can you show ANY benefit to this today? It just doesn't make any sense in any car that can be street driven!

Contrary to what you may consider the norm for most of todays street driven engines....many builders still like .0025 main and rod bearing clearances for high rpm street/strip applications. If you find that shocking you'll be questioning my piston to wall clearances as well....those run at .006 

Ok, so you're wondering why ? Easy.....heat = thermal expansion....simple as that. I like to use a thicker dyno oil and use wider clearances and a hv pump to pick up the slack. That's just my preference....but i know many who do the same and have excellent results. Personally, i don't buy into the whole parasitic loss arguement....sure ther is some but not as much as most think. Your arguement about race engines might buy into that theory but we're talking street engines here where that last bit of HP isn't being chased. Personally, i'd rather have lots of oil on the crank and cam to keep things happy. The Mopar splash lube cam oiling is a poor design so the more oil you get slung up there the better. This is also why i'm not a fan of low idle speeds.  Of course i' referring to flat tappet cam technology....none of this applies to roller cams.

Oil pressure at idle speed is very important....the more the better, inmo. With a flat tappet cam i like to see at least 35-40 psi hot. 


Regarding volume vs pressure. Increasing the volume through a fixed orifice will increase pressure. This is the same basic theory that is applied to fire engine pumps....i have a little experience in that area too.  The HV pump will bypass anything the engine won't need just like a stock pump will....that i will agree on. I prefer to err on the side of caution when it comes to lubrication....protecting the bottom end is priority #1. If it costs me a few hp in crank output....so be it. I have only seen one broken oil pump drive over the years. That piece was in a high rpm combo (it was 25+ yrs old) and had many dragstrip passes before it sheared off....major abuse. I would hazzard to guess that the average guy could run a stock OP drive as long as he wasn't beating it to death every weekend at the track. The hardened drive is only $75.00 so it's not a big deal if you feel the need to upgrade....pretty cheap when you consider the several thousands you spend rebuildng and maching an engine. For a cruiser application i wouldn't even worry about it....but that's just me.


Back to the subject ; Natcho....i would use the HV pump w/o reservation. This doesn't sound like a race build so i wouldn't be concerned about the hardened drive either. Fwiw, the OP drive that's in mine is an stock unit that is 25+ yrs old and who knows how many thousands of miles. We made 85+ dyno passes to 6500 rpm with the HV pump (80 psi) and the "old" OP drive had zero problems. I will be changing it out to a hardened drive because this engine will see lots of strip action in the future....way more abuse than the average guy will ever put his through. 



Ron

[dave571]

I will say I agree with the bulk of "is it ever done"'s comments.


I will add, that I have found that hv pumps usually have a higher pressure spring in them.  I have found that they can lead to excessive oil pressure on a fresh motor.(have had to put a std pump back on a couple of fresh motors)  Real world observation, so take it for what it's worth.

I don't run one in my 64 dodge with 440.  11 second car.  Hits 50 pound under hard accell.  a little more above 5k



A couple of  brief points....

-It is a myth that a hv oil pump provides 'better' lubrication, for many of the reasons already given.  As mentioned earlier, HV pumps were designed for restoring oil pressure in worn engines (excessive clearances)  Motors with tight factory specs, don't need one.

-Standard volume pumps are easily available.  The guy who sells the melling HV's in  your area, can get the melling std volume too.  just ask him to to order one in.  Same part number, without the hv on the end.  It will be a little cheaper than the hv. 

Lastly...
I had an experience last month that lead me to believe I will NEVER run a HV pump again.

I assembled a 76 440 on the cheap for my old 74 d200.  Low mile motor with little wear on the rotating assembly.  I put new brgs in it with no machining to the crank or rods.    Clearances in the .0025- .003 range on the mains.

Put it together with a new pump that had been unused  on my shelf for some years.  STD volume, brand I will not mention.

pressure relief was stuck in the pump(unknown to me at start up).

At 1500 rpm it made enough pressure to immediately blow the oil filter up like a balloon and destroy it.

Tapped the pump with a hammer, and popped on a new filter.
NOW at idle(800 rpm), enough pressure to overcome the flat seal from filter to the pump, peg the gauge,  and shower my garage with oil like a gisser(sp?)

So even in an engine with NO machining, and worn parts, a standard pump moved so much oil(with the relif stuck) , that it could make several times the required amount of oil pressure, at only 800 rpm engine speed.

Why would I want  an HV?

Just some food for thought

[Nacho-RT74]

-Standard volume pumps are easily available.  The guy who sells the melling HV's in  your area, can get the melling std volume too.  just ask him to to order one in.  Same part number, without the hv on the end.  It will be a little cheaper than the hv. 

If that comment is to me, I'm outside USA... I'm in southamerica. Pump was a VERY OLD STOCK piece located on a machine shop. In fact, the melling box was too old that still have the oooooold emblem i think with a dog on it as I can recall, and box was practically destroyed by dust and humidity .

And Ron the one I found is an HP, not HV . anyway I just bought it for replacement part storage, not because I really need. If I find an HV volume sure I will go for it too. I'm still thinking on 451 stroke but not for race anyway, at least not proffesionally, but could it be for exhibition race, just street in my mind really, so that was the reason I'm asking about HV or HP comparison.

still searching locally a 440 crank, iron or steel no matter which one.

It looks there is a nice discussion here, and still no conclussion