I've heard it both ways...which one do you think is better and what is your reasoning behind that???
Do you have any hard facts or just go by what you've heard?

 

better for what? a lot depends on your application.

 

If the PRESSURIZED part of the oil system has not been modified, then a high-volume pump is not necessary; and will not provide any benefit, but will only create extra problems.

The oil system will only flow as much oil as the parts that it feeds, allow through it. Think of it as being like hooking your bathroom faucet up to the end of a water main: doesn't matter how much water the main can flow, the only water that can get out, is what goes through the faucet. Which means, increasing the water main from 4" to 10" diameter, won't make a single additional molecule of water flow through the main, because every molecule has to come out that faucet. For that matter, if it was ½", increasing it to ¾" probably wouldn't even change the flow; because the ½" line is already delivering as much water as can possibly go through the faucet.

Same with your oil system. Oil escapes from it by going through the bearings (mains, rods, cam), through and around the lifters, and around the distributor housing. In a stock block, that's IT. If your motor has no additional oil leaks, then a stock volume pump is plenty adequate.

Modifications that MIGHT increase the flow volume through the oil system:

• Grooved main bearings
• Cross-drilled crank
• Excessive bearing clearances
• Pressure-fed solid roller lifters

If you have none of these things, then you don't need a high-volume pump. At best, all it will do is use up a couple extra HP turning it, and increase the load on the distributor gear which will wear it out faster and cause more erratic timing.

If a motor has low oil pressure, there's a reason; and if it hasn't been modified as described above, then a high-volume pump isn't the solution.

 

+1, I put a HV Melling in my motor when I built it, before I knew better. Its a higher rpm combination and I turn it to 6600 at the track, I know that pump and my lack of windage tray is killing me. Not to mention, that HV pump trying to force more oil where it couldnt flow, made my oil pressure rise like crazy. WOT I get 80 psi, cruise is around 60.

EDIT: Also, if this counts for something, I know a guy with a carbed blow-thru stroker motor making ~1200 to the wheels running 9's in the drag radial class, and you know what oil pump he runs? Yep, stock.

 

1200 at the wheels only turning out 9's?

I thought the half of the main bearing that goes into the block is always grooved. Mine is.

Heres a great post thanks to grumpyvette...(basically says over 400hp and 6000rpm HV will only help if you have the means to control it; oil return passages not blocked, baffled pan, over 5 qt oil cpacity, and a windage tray and crank scraper really help).

"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, yes its possiable for the crankshaft WITHOUT A WINDAGE SCREEN to keep acting like a propeler and pulling oil around with it in the crank case but thats what the wrap around style milodon type windage screen is designed to stop)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 NEEDs 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. [color:"red"] 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 [/color] that have an oil pressure feed distributor shaft bearing.)
so the more oil voluum the better,(AS LONG AS ITS TOTALLY UNDER CONTROL ON BOTH THE PRESSURE AND RETURN/SCAVAGEING SIDES OF THE SYSTEMchevy 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.

Continued (oil Pan/pump)
the oil pump can only pump as much oil as the engine clearances allow at the max pressure that the oil pump bye -pass circuit will allow, and no more. for your idea to be correct (which it could be under some conditions)the oil flow through the engine clearances would need to be so great that the pump turning at 3500rpm,7000rpm engine speed(remember the pump spins 1/2 the speed the crank does)and most likely pumping at max pressure could lower the oil level to the point that the pick-up becomes uncovered or a vortex as you call it forms and the pump starts sucking air.


now under hard acceleration it is very possiable for the pickup on ANY oil pump to to become uncovered in a oil pan that has less than 5qt capacity and with no oil control baffles as the oil rushes to the rear of the oil pan if the pick-up is located in mid pan or under hard brakeing if the pick-up is located at the rear of the pan on a non- oil baffle controlled pan.

I will grant you that it is possiable for ANY oil pump to pump a good amount of oil into the lifter gallery at high rpms IF THE OIL RETURN PASSAGES IN THE HEADS AND LIFTER GALLERY ARE BLOCKED, preventing its normal return to the crankcase

, but running a high volume oil pump will have little or nothing to do with how much oil is in the pan if the engines drain back holes are clear and your useing a milodon style windage screen. I have several times had that same complaint about lack of oil pressure under acceleration but it is caused by a non-baffled pan or the pickup mounted so close to the pan bottom that the pump cant get a good intake flow, if you carefully check youll find that on a dyno runs it seldom happens,because the oil is constantly removed by the windage screen is returned to the sump, most of the oil pumped into the system exits at the rod and main bearing clearances or at the cam bearings and from the lifter bores lower ends, its not the constant oil flow or lack of oil into the rocker arms that has the big effect on total oil flow as SMOKEY YUNICKS PHOTOGRAPIC RESEARCH PROVED YEARS AGO,its the oil flowing from the bearings and lifters and that oil flow is quickly returned to the sump by a windage screen scrapeing it off the spinning crank and rods as the spinning assembly passes over the windage screen. in effect most of the oil in an engine works like your timeing chain in that it constantly cycles top to botton and back never getting higher than the cam bearing lifter area.

[color:"red"] now what does quite frequently happen [/color] is that the guys installing a high volume oil pump just swap out the standard pump, reinstall the stock or simular pick-up and bolt on the pan with the pick-up in the stock possition on the oil pump. the stock pick-up is mounted about 3/8" off the pan bottom,the high volume pump is normally equiped with impeller gears about .3 inches longer than stock, the high volume pump body is that much lower in the pan, resultting in the pick-up being only about 1/8" from the pan bottom. the result is that on a normal chevy oil pump pick-up this leave a space of about 1/8" x 2.5" for oil to flow into the pump. at low rpms this works but as the rpms climb the pick-up that can,t get any oil to pump cavitates as it spins and fails to pump oil, result oil pressure drops untill rpms are lowered no matter how much oil is over the pick-up. simply checking to make sure that anout 1/2" of space is under the pick-up when the pan is installed cures that problem (a simple trick is to weld a 1/2" thick nut to the oil pump Pick-up base and test fitting the pan BEFORE WELDING THE PICK-UP TO THE PUMP BODY)

what it comes down too in every case that Ive looked into so far is a improperly positioned pick-up or a non- baffled oil pan without a windage screen or less than 5 qts of oil in the system, not a problem of all available oil being pumped into the lifter gallery and valve covers like some people would like you to think.

the MELLING COMPANY HAS THIS TO SAY

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.

[/color] let me point out this chart





Bearing Clearances
heres other info,
http://www.babcox.com/editorial/ar/ar10180.htm

Examples of Engine Bearing Failures

Engine Oil

http://www.jimcookperformance.com/Te...s/TN%2023.html




http://www.cryoeng.com/images/Engine...itySecrets.htm

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

Engine Rebuilding for the Repair Shop, Larry Carley, Underhood Service, October 1999


.
Crane suggests cutting a .030-inch-wide by .030-inch-deep slot in the lower band of the distributor housing to direct a spray of oil onto the camshaft and distributor gears. Use a Dremel tool to cut the slot into this distributor.

ITS just a tip for improving the oil flow to the distributor, BUT it HELPS a good deal with cam/distributor gear life so its a STANDARD MOD I always do!(keep in mind youll want the grouve location to spray oil into the gear teeth contact area , moving the distributor timing moves the oil spray area so the CAREFULLY CUT grouve in the block seems like a better IDEA"

 

And what about the high pressure pumps??? All the debate seems to go to the high volume vs. stock.

 

A high pressure pump just has a stiffer bypass spring.

 

CamarosRUS....it'd be an 8 second car but it's a hatchback GT, not an LX, and he's running in the drag radial class so he doesn't hookup all that well. Trust me, the car will get out of its own way. I still dont think he's driving it to what it's capable of though, I talked to him a month ago and he told me he's still afraid of it. It's a carbed blow-thru 347.

 

A high pressure pump may or may not help. The rule-of-thumb is 10 PSI for every 1000 RPMs. So a stock oil pump that only gives 45 PSI might not be quite enough pressure for a motor that's going to turn 6500. Keep in mind, it's just a rule of thumb, not a guarantee.

Higher oil pressure = higher bearing speeds possible (RPMs)

They go hand-in-hand.

Higher volume? Really depends on your various oil clearances and what all the parts NEED in terms of volume. A stock volume pump will work just fine on most street engine combos. I almost always run a stock volume pump.

 

Nixon...I would defenitly be afraid of 1200rwhp. If it hooked you would be on two wheels verticaly before you could crap your pants!


So from what I understand (to summarize for everyone) high volume pumps are only needed if you have done modifications that need an increased amount of oil into the motor and have the means to control it/drain it back down quickly. A high pressure pump is always a good idea. The prefered setup is a standard M55 with the Mr. Gasket #26 high pressure spring.

I was running a M55A (the "Z28" high pressure pump) and had a couple problems (oil pump shaft collar rubbing and throwing metal in the oil PLUS a cracked lifter) but was only getting 10 PSI hot idle. The pump is practically new should I clean it out and throw it back on or get a new M55?

 

The pump draws up unfiltered oil, so if there was metal in the oil, the pump gears could be worn. You could open it up and check, but oil pumps are relatively inexpensive anyway.

 

this whole thread makes my engine sound over oiled...

i have the melling m55HV high volume pump, with the GM high pressure spring...

In some instances my clearances were a bit large, but ntohing major, my rod side clearance seemed way out of wack, but ended up just being a cooling effect with the extra flow of oil...


At a warm idle i have a 80psi oil system, yeah i know, at 190* 80psi is rediculous... at full throttle, i cant find a guage thats not pinned... i've found a guage rated at 150psi, and well. it was pinned.

Yes i know, its stelaing some HP, but at the same time, its keeping my engine alive and well... my mains should look like they've never been installed...

My rockers will squirt a good few feet...

eventually tho, i plan to fun a blower or turbo, some sort of system that requires auxillary oiling, and well. i have the flow capability...

 

I have 3 out of the 4 things that would make sense with me running the pump I do (i dont have the lifters). But I didn't go all out with the pump, I went SLIGHTY over stock, with a high volume but not that much more pressure.

 

hmm, yea, that's what I did.... What does that do anyway? The stiffer bypass spring? I put it in on sofakingdoms recommendation, and didn't really think about it.... Just kinda strains the dist, and forces it to pump out oil under higher pressure?
My oil pressure was pegged at 60 on hot starts, then after warming up would go down to 45... But lately has been going down to 30... Must be the synthetic multi-grade oil i'm using, rather then the conventional straight 30W.... Or the flattened cam

 

Excessive oil pressure will damage things, not help things

 

Interesting reading here with lots of technical information but I think it would be much better to have a technical response. No offense but without any technical information its hard to follow rather than just saying thats how it is. I would like to hear an explanation of what damage would occur other than the worn out distributor gear.

 

You could also damage the pump arm that runs from the bottom of dizzy to the oil pump itself UNLESS you run the steal collared pump arm, unlike the plastic one that most cars come with stock. And if that breaks then there is NO oil pressure...and you can imagine that nightmare.

Also the pump may suck all the oil out of the pan if you aren't running a bigger pan to hold more oil, which again leaves you with no oil pressure and engine damage.

You can also wear out passages over time, and cause spun bearings due to too much oil pressure and it may get behind bearings cause them to come loose and spin around.

 

All high pressure pumps seem to come with the steel collar though and the instruction actually make it a point to use it.

Noone ever seems to agree with this and I have heard on some occasions even by the manufacturer that this is a myth.

Is that really true? I have never heard that before.

 

I am talking MANY miles and such, think of how water can wear rocks in a steam, now seal that flow in a high pressure tube and run it over the same areas again and again.....eventually something wears. Thats more a theory I have heard about high mileage motors and such.

And as for the collar, think of how many people who get a pump and no collar go and buy one, or dont have the money to spend on a steal collared one.

 

I use melling 55 HV pumps. Ive never had any issues with using one or ever ran the sump dry. As long as it isnt a roundy roundy car and your not using the incorrect pan/sump you will be fine. Melling Engine Parts has all the tech info you need and since they make them they know a bit more about thier product then a bunch of bench racers spitting monkey snap out thier .

 

Yes unless you have the extra clearances that require higher pressure, you don't need it. Bearings are soft and excessive pressure at all times can shorten their life.

 

I dont understand because I read that high pressure pumps dont actually put out any more than a standard pump just when needed at higher rpms. I dont see how this is possible from an engineering point of view. Where exactly are you getting this information? Do you have any hard evidence? Are you able to provide actual tests that were done? No offense I dont know you and just because your saying this doesnt convince me at all. From what I understand the high pressure pump will only create a higher pressure when it is needed under high load. Its not pressurizing the system its just preventing it from relieveing under higher loads when the engine has gone beyond the standard street rpm.

 

Your right, I havent read the whole thread but no one seems to of said otherwise. All that makes the pump any different is a stiffer spring and, in some cases, different gears in the pump (thats for REALLY high rpm motors)

 

Now Z28s had a high pressure pump. Does this mean when they built Z28 engines they had looser tolerances? Did Z28 engines need more frequent repairs due to bearing failures?

 

didnt the z28 motors also rev to a high RPM??

 

You'll kill the bearings with excessive pressure which will end up blowing the oil right out the sides of the bearings rather then distribute evenly

 

Thats understandable. But my previous questions were not answered and a high pressure pump does not produce high pressure at all times like previously stated. Does anyone know if Z28s had looser tolerances and if not were they prone to bearing failure? I would think this would validate wether high pressure pumps would create problems or not.

 

GM's reasoning for this was because of the powerband of the old 302s. They were built to spin alot higher than a typical 327 or other SBC made at the time. Most were 'done' by about 4500rpm, but the Z28s were supposed to spin to 6500+ because they were Trans Am motors. The higher pressure pump was used because of this.

The extra oil pressure was only at high rpms though, because it just used a stiffer spring. At 'normal' rpms, the oil pressure is the same as a typical SBC.

 

The bypass spring sets an upper limit on the oil pressure by letting the pump recirculate oil internally when the pressure in the oiling system reaches the desired limit.

The oil pump is a positive displacement pump. It moves the same volume of oil on every rotation. If the clearances in the oiling system are tight, it will be hard for that volume of oil to be squeezed back out in the pan, so the oil pressure will be high. If the clearances are loose, the oil pressure will be low.

A high volume pump will produce more oil pressure than a standard pump, up to the pressure of the bypass spring. After that, they behave the same.

 

How much pressure is the stock unit capable of out of curiosity? I dont think I will be having any problems shifting at around 6000rpm with stock am I?

 

depends on the pressure regulator spring...