NoWorries

What makes an oil pump high volume? I have a Melling high volume pump sitting on my tool box. In the car is an OE-style Melling Pump.

The case looks identical...thats as deep as I've gotten.

I want to convert the stock pump into a high volume. What's different? Are the impellors different? I know the spring has something to do with volume/pressure, could I just change that out and expect high volume/pressure?

The reason I'm not doing a straight swap is that the pickup is welded all the way around the pump now, and a new pick-up is at least a week away from me being able to get it.

Thanks.

joalyons

Im not 100% sure about the difference, but I think the springs raise pressure (which you don’t need in a SB Chevy). Im not sure how "high volume" works. Bottom line though, in many cases you don’t need either, just blue print a stock pump (take the cover off and make sure the tolerances are correct between the gears and the cover) and you will be happy with the pressure, and although you can measure it, my machine shop and motor buddies tell me the volume will be more than adequate. So from your post, I would blue print the high volume pump and be done with it.

Sharky Guam

The amount of oil displaced by the impellers makes it a high volume pump. Some pumps have bigger pickup tube sizes. The spring only regulates bypass pressure.

:cheers:

grumpyvette

if you measure the impellers the high voluum pumps impellers are about .3" longer in length, if you look closely at a standard oil pump, placed next to a high voluum oil pump body you will notice the differance in hight/thickness of about .3", now I hear over and over again how high voluum pumps can pump your oil pan dry,wear distributor gears,ETC. ....B.S. SMOKEY YUNICK, doing research for G.M. took high speed photos of engines turning in the 7000rpm range , equiped with clear plastic oil pan windows and valve covers and, guess what , even at sustained 7000rpm PLUS useing a high voluum oil pump the valve covers dont get over 1/3 full of oil, the pan still has most of the hot oil in it because the oil returns/flows to the pan fairly quickly, if there no restrictions in the oil return , drain back holes, SMOKEY ADVISED that you only need a Z-28 oil pump in his book (POWER SECRETS) but look closely at the oil pump in the picture of his road racing car engine with the swinging pick-up (yeah thats right! its a BIG BLOCK OIL PUMP!)

Most of the stock automobile engines are designed to operate from idle to 4500 RPM. The original volume and pressure oil pump will work fine in this type of application. As the demands on the engine increase so does the demands on the oiling system and pump.
The oil pump's most difficult task is to supply oil to the connecting rod bearing that is the farthest from the pump. To reach this bearing, the oil travels from three to four feet, turns numerous square corners thru small holes in the crankshaft to the rod bearing. The rod bearing doesn't help matters. It is traveling in a circle which means centrifugal force is pulling the oil out of the bearing.

A 350 Chevy has a 3.4811 stroke and a 2.111 rod journal. The outer edge of the journal travels 17.5311 every revolution. At 1000 RPM, the outer edge is traveling at 16.6 MPH and 74.7 MPH at 4500 RPM. If we take this engine to 6500 the outer edge is up to 107.9 and at 8500 it is 141.1 MPH. Now imagine driving a car around a curve at those speeds and you can feel the centrifugal force. Now imagine doing it around a circle with a 5.581, diameter.

The size of the gears or rotors determines the amount of oil a pump can move at any given RPM. Resistance to this movement creates the pressure. If a pump is not large enough to meet the demands of the engine, there will not be any pressure. Or if the demands of the engine are increased beyond the pumps capabilities there will be a loss of oil pressure. This is where high volume pumps come in; they take care of any increased demands of the engine.

Increases in the engine's oil requirements come from higher RPM, being able to rev faster, increased bearing clearances, remote oil cooler and/or filter and any combination of these. Most high volume pumps also have a increase in pressure to help get the oil out to the bearings faster.

That is what a high volume pump will do. Now let Is consider what it will not do.

It will not replace a rebuild in a worn-out engine. It may increase pressure but the engine is still worn-out.

It will not pump the oil pan dry. Both solid and hydraulic lifters have metering valves to limit flow of the oil to the top of the engine. If a pan is pumped dry, it is because the holes that drain oil back to the pan are plugged. If the high volume pump is also higher pressure, there will be a slight increase in flow to the top.

It will not wear out distributor gears. The load on the gear is directly related to the resistance to flow. Oil pressure is the measure of resistance to flow. The Ford 427 FE "side oiler" used a pump with relief valve set at 125 psi and it used a standard distributor gear. Distributor gear failures are usually caused by a worn gear on a new cam gear and/or worn bearings allowing misalignment.

It will not cause foaming of the oil. With any oil pump, the excess oil not needed by the engine is recirculated within the pump. Any additional foaming is usually created by revving the engine higher. The oil thrown from the rod bearings is going faster and causes the foaming. This is why high performance engines use a windage tray.

It will not cause spark scatter. Because of the pump pressure there is a load on the distributor gear. The number of teeth on the oil pump gears determine the number of impulses per revolution of the pump. In a SB Chevy there are seven teeth on each gear giving 14 impulses per revolution. At 6000 RPM the oil pump is turning 3000 RPM or 50 revolutions per second. To have an effect on the distributor, these impulses would have to vibrate the distributor gear through an intermediate shaft that has loose connections at both ends. Spark scatter is usually caused by weak springs in the points or dust inside the distributor cap.

High volume pumps can be a big advantage if used where needed. If installed in an engine that does not need the additional volume, they will not create a problem. The additional flow will be recirculated within the pump.

ALSO READ THIS
http://www.melling.com/engoil.html





the MILODON PEOPLE HAVE THIS TO SAY

Milodon Hi-Volume/Hi-Pressure Oil Pumps provide a 20% to 30% increase in performance both in volume and pressure. And most heavy duty and performance applications require an increase in both areas. Increased bearing loads, increased RPM and horsepower all place greater demand on the oil system which, if not up to the job, can cause very premature engine failure. All Milodon oil pumps are 100% flow tested to assure you the quality your engine demands.

and MOROSO

http://www.moroso.com/catalog/catego...?catcode=14444

ok lets look at a few things, pressure is the result of a resistance to flow , no matter how much oil is put out by the oil pump there is almost no pressure unless there is a resistance to that oil flow and the main resistance is from oil trying to flow through the bearing surface clearances and once the pumps output pressure exceeds the engines ability to accept the oilflow at the max pressure the oil return system/bypass spring allows the oil circles back through the pump ,now the amount of oil flow necessary to reach the furthest parts in the engine from the oil pump does not go up in direct relation to rpm, but it instead increases with rpm at a steadly increaseing rate that increases faster than the engine rpm due to centrifugal force draining the oil from the rods as they swing faster and faster since energy increases with the square of the velocity the rate of oil use goes up quite a bit faster due to the greatly increased (G-FORCES) pulling oil from the rod bearings over 5000rpm going to 8000rpm than the rate of oil flow increases from 2000 rpm to 5000rpm (the same 3000rpm spread) and remember the often stated (10 lbs per 1000rpm)needs to be measured at the furthest rod and main bearing from the pump not at the pump itself, next lets look at the oil flow itself, you have about 5-6 quarts in an average small block now the valve covers never get and hold more than about 1/3 to 2/3 of a quart each even at 8000 rpm (high speed photography by SMOKEY YUNICK doing stock car engine research with clear plastic valve covers prove that from what Ive read) theres about 1 quart in the lifter gallery at max and theres about 1 quart in the filter and in the oil passages in the block, that leaves at least 2 quarts in the pan at all times and for those that want to tell me about oil wrapped around the crankshaft at high rpms try squirting oil on a spinning surface doing even 2000rpm (yes thats right its thrown off as fast as it hits by centrifugal force)the only way to run out of oil is to start with less than 4 quarts or to plug the oil return passages in the lifter gallery with sludge or gasket material!now add a good windage tray and a crank scrapper and almost all the oil is returned to the sump as it enters the area of the spinning crankshaft! forming a more or less endless supply to the oil pump, BTW almost all pro teams now use DRY SUMP SYSTEMS WITH POSITIVE DISPLACEMENT GERATOR PUMPS that are 3,4,or 5 stage pumps each section of which has more voluum than a standard voluum oil pump because its been found total oil control is necessary at high rpms to keep bearings cool and lubed

NOW I POSTED THIS BEFORE BUT IT NEED REPEATING
ok look at it this way,what your trying to do here is keep an pressureized oil film on the surface of all the bearings to lube and cool them and have enough oil spraying from the rod and main bearing clearances to lube the cam and cylinder walls/rings. now a standard pump does a good job up to 5000rpm and 400 hp but above 6000rpm and 400hp the bearings are under more stress and need more oilflow to cool and because the pressure on the bearings is greater you need higher pressures to maintain that oilfilm.lets look at the flow verus pressure curve. since oil is a liquid its non-compressable and flow will increase with rpm up to the point where the bypass circuit starts to re-route the excess flow at the point were the pressure exceeds the bypass spring pressure. but the voluum will be equal to the pumps sweep voluum times the rpm of the pump, since the high voluum pump has a sweep voluum 1.3-1.5 times the standard pump voluum it will push 1.3-1.5 times the voluum of oil up to the bypass cicuit cut in point,that means that since the engine bearings leakage rate increases faster as the rpms increase because the clearances don,t change but the bleed off rate does that the amount of oil and the pressure that it is under will increase faster and reach the bypass circuit pressure faster with the high voluum pump. the advantage here is that the metal parts MUST be floated on that oil film to keep the metal parts from touching/wearing and the more leakage points the oil flows by the less the voluum of oil thats available for each leakage point beyond it and as the oil heats up it becomes easier to push through the clearences.now as the rpms and cylinder preasures increase in your goal to add power the loads trying to squeeze that oil out of those clearances also increase. ALL mods that increase power either increase rpms,cylinder preasures or reduce friction or mechanical losses. there are many oil leakage points(100) in a standard chevy engine.
16 lifter to push rod points
16 pushrod to rocker arm points
32 lifter bores 16 x 2 ends
10 main bearing edges
9 cam bearing edges
16 rod bearing edges
2 distributor shaft leaks
1 distributor shaft to shim above the cam gear(some engines that have an oil pressure feed distributor shaft bearing.)
so the more oil voluum the better.chevy did an excelent job in the design but as the stresses increase the cooling voluum of the extra oil available from the larger pump helps to prevent lubracation delivery failure, do you need a better pump below 5000rpm or 400hp (no) above that level the extra oil will definitely help possiable deficient oil flow and bearing cooling and a simple increase in pressure does not provide a big increase in voluum that may be necessary to keep that oil film in the correct places at the correct voluum at all times.the stock system was designed for a 265cid engine in a passenger car turning a max of about 6000 rpm but only haveing the stress of under 300hp transmitted to the bearings, Im sure the orriginal designers never thought that the sbc or bbc would someday be asked to on occasion hold up to 450-800hp and 6000-8000 rpm.nore did they forsee valvesprings that placed 500lbs and up loads on the lifters and the use of over 9 to 1 compression ratios in the original design so the oil voluums and pressures necessary to cool those valve springs and bearings at those stress levels were never taken into account for that either.


http://www.melling.com/miscon.html
http://www.melling.com/highvol.html
http://www.melling.com/engoil.html


[Modified by grumpyvette, 1:05 PM 7/24/2002]

grumpyvette

BTW in almost every case where someone tells me that their looseing oil pressure at high rpms because the pumps pumping the pan dry Ive found after careful investigation that
(1) their oil pump pickup was mounted too close to the bottom of the oil pan restricting intake oil flow or was loose and had moved down enough to touch the oil pan floor.
(2)they were useing a NON- baffled oil pan and the pickup was becoming uncovered due to oil running to the back or front of the pan durring accelleration or brakeing
(3)they had less than 5 QTs in the oil pan( plus #1 and #2)
(4)AND IN MOST CASES they were not useing a windage screen that greatly speeds the oils return to the oil pan sump, which is a great idea in any engine thats spun up into the 6000rpm and over range!
(5) if your going to use a high volume oil pump to insure oil is getting to the bearings at 6000rpm PLUS you NEED to use one of these windage screens to FORCE the rapid ,efficient, and effective oil control necessary to return that oil to the sump for recylcling into the engines system http://www.jegs.com/cgi-bin/ncommerc...41&prmenbr=361

NoWorries

Thanks for the very comprehensive reply. :) Thats exactly what I was looking for and why I love this forum. :cheers: It should be put in the tech tips, I've seen this question come up a few times and this is the best reply.

I need to install a high flow pump because I just added 10+ ft of tubing in an oil cooler, about 1/4 of that is uphill.

Unfortunately I've been completely bogged down with the AirForce since Tuesday so I haven't had time to drop the pan, I also installed the radiator wrong and have to pull the shroud. My car is never going to get done...

Thanks again.