high volume oil pump?

[HICKL]

I am building my 350 using a kit that includes a melling high volume oil pump. A friend of mine warned that he had probs with this pump emptying the oil pan at high RPM's. Anybody got any feedback on this? My motor will not be very radical (325 hp ish). What should I do?

 

Jeff

[Mudge]

I have not yet heard a good case for a high volume pump, ever. In fact like your friend I have heard nothing but "stay away" about these pumps.

 

If you have a hyd cam then stick with a standard or high pressure pump, most of them are high enough and flow quite handily enough. If you go solid you actually will often find restrictors keeping less flow to the top.

 

I would get a standard high quality pump.

[Mike C]

I agree with Mudge. The SBC has a very efficient oiling sytem and performs quite well in stock form with good parts. I would buy a Melling oil pump for a Z/28 ('69 302) I believe # is ME55v vs. the standard ME55, but it has been awhile. Definitely replace the oil pump driveshaft with an aftermarket one with a metal collar.

[utvolman99]

What I have heard and what Im doning for my engine is using a high volume pump with a 7qt pan. I am using the HV because thats what came with my kit. I have heard that he HP is more practical but haveing more oil in your pan is important if your using a HV oil pump.

[grumpyvette]

IVE POSTED MOST OF THIS BEFORE BUT IT FITS HERE AS A SOURCE OF INFO FOR THE NEWER GUYS

if you have the chance go an get a better baffled higher capacity oil pan that is engineered to control the oil supply better, NOTICE not once did I say spend tons of money, please pay attention while I prove my case!

short answer is NO YOU MOST LIKELY DON,T NEED a HIGH VOLUUM OIL SYSTEM BUT ITS ALWAYS A GOOD IDEA! look at it this way, theres no way a high voluum oil pump can pump more oil through the engines oil passages than the voluum the clearances allow at the max pressure that is supplied by the pump, read the info below

 

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

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

 

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. 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,(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.

 

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.

 

now what does quite frequently happen 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.

 

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.

BTW

> The bottom of a Chevrolet distributor housing can be modified to spray pressurized oil onto the distributor drive gear. The extra lubrication will reduce distributor gear and camshaft gear wear. This is especially important when the gear is used to drive non-standard accessories, such as a high volume oil pump, or a magneto that puts additional loads on it and the cam.

 

When the distributor is installed, the bands at the bottom of the housing are designed to complete the internal right side lifter galley on all small and big block Chevrolet V-8’s and 90° V-6 engines. If you hand file a small vertical groove .030" wide x .030"( thats the diam. that crane recommends Ive always used the larger groove with no problems)deep on the bottom band (above the gear), pressurized oil running between the two bands will be directed downward onto both the gear and the cam. This procedure is recommended for all Chevrolet engines no matter what material gear (cast or bronze) or what type of camshaft (cast or steel) you are using. keep in mind the groove MUST be lined up with the cam gear when the distrib. is installed the oil SYSTEM is just that... [color:"red"] a SYSTEM, a system, where ALL the parts must match, [color:"blue"] since oil is non-compressable fluid and oil pressure is restricted to the max pressure limit set by the bypass circuit cut-in point , the oil pump will pump and can only pump the amount of oil the clearances and oil bleed off rate allows, if your engine needs more oilflow and the stock pump can,t keep up with demand the pressure WILL fall, but if the pump supplies more than necessary not much bad happends except a possiable loss of max horsepower due to a couple hp (2-4hp) produced being wasted pumping extra oil through the bypass circuit, COMPARED to when not enough oil reaches the bearings........ ( WHICH RESULTS IN TOTAL ENGINE FAILURE)[/color] if your going to pump oil in maybe 5%-10% higher voluum (and thats only true if the engines clearances allow it) at the mid and upper rpm levels to MORE EFFECTIVELY COOL AND LUBERACATE the BEARINGS AND VALVE SPRINGS you must also return that oil voluum to the sump about 10% or more faster at ALL rpm levels [/color] you must be aware that if you install a high voluum pump you will also be much better off installing a windage screen like MILODON makes

 

 

( a windage screen DESIGNED to return oil efficiently to the oil pan sump for quick, effective RECYLCLING thru the system )and makeing VERY SURE the oil pump pickup is 3/8"-1/2" OFF THE oil pans lower surfaces AND that the oil drain back holes are clear , also keep in mind that a baffled high voluum oil pan is ALWAYS A GOOD IDEA, heres a reasonably nice one for the money, that can fit or be modifyed to fit many cars

 

http://www.midwestmotorsportsinc.com/mms.nsf/pages/Specials

and there are "KITs" available to weld a larger or wider sump to stock oil pans

[Mudge]

Thanks for that LONG post Grump

[HICKL]

Is that a yes?

[Guest Anonymous]

Do a search on Mr. Grumps posts where this question was visited before and url's were posted on high capacity oil pans not costing personal body parts. If you are using a high volume oil pump,get a higher capacity baffled oil pan and a good windage screen.

[niceguy678us]

.................

[grumpyvette]

BTW

as a general rule youll want to run the thinnest weight oil that will maintain about 20 lbs of oil pressure in a hot (200f)engine at idle, remember oil flow over the bearings COOLS by ABSORBING HEAT and carrying it into the oil pan, oil cooler or letting the cooler block surfaces absorb the heat for the cooling system to remove, to cool the bearings and lifter contact points ETC. the greater the voluum of oil flowing over the bearings the more heat can be carried away and the more constant the surface temp. can be. and be fore someone jumps in with that old myth that oil flowing over the surfaces to fast will fail to pick up the heat from the bearings... let me point out this chart

 

 

http://www.diabolicalperformance.com/clearances.html

heres other info,

http://www.babcox.com/editorial/ar/ar10180.htm

 

http://www.thirskauto.net/BearingPics.html

 

http://www.waynesgarage.com/docs/oil.htm

 

http://www.jimcookperformance.com/TechNotes/TN%2023.html

 

http://www.cryoeng.com/images/EngineDurabilitySecrets.htm

 

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

 

http://members.aol.com/carleyware/library/engine2t.htm

[HICKL]

Mr Grumpy Sir, would you just build my car for me. I now realize I am to ignorant to be turning wrenches. Just kidding, thanks for the in-depth information. I wish I had half your knowledge. Of course I would just forget it.

[grumpyvette]

since I broke my ankle last year I have not been taking on any new jobs unless I can watch and instruct personally whats going on with the person who owns the car doing 90%-99% of the work as I can,t stay on my feet more than a minute at a time, hopefully the damn ankle will heal shortly so I can get back to doing what I enjoy, building engines!(I also have not been chargeing anything for the work as that would not be fair)

 

BTW on the high voluum pump versus the standard pump, what Im saying is basically this

if you push the oil at a low enough pressure and voluum accross the bearing surfaces the limited , stock oil voluum ,compared to the higher , voluum pumped by the aftermarket pumps, passing over the surface will ,pick up a higher heat transfer per oil voluum in contact with the bearing surfaces due to its longer contact time.

that poses three minor potential problems that might be major potential problem depending on the temp. range and oil quality (mineral versus synthetic)

 

(1)as the oil voluum passing over the bearing surface heats up it can absorb a lower percentage of the bearings heat

 

(2)as oil heats up it breaks down and by the time mineral base oils hit 260 degrees they have lost significant luberacation

 

(3)oil picks up and carries micro trash (carbon,acids, metalic dust,etc.) that can embed in the bearing surfaces, a slightly higher pressure and voluum flowing accross the bearing surfaces TENDs to keep them cleaner because the FILTERED oil PUSHED OVER THE BEARING SURFACES tends to be run through the FILTER more often

so if your pushing 20% more oil at 10% greater pressure accross the bearings the oil will tend heat slower,have a greater time in the cooling off cycle and stabilize at a lower total heat absorbsion level.

 

what most of the guys that tell you a stock pump is all youll ever need FORGET to TELL you is that

the high voluum pumps pump oil to the bearings faster at startup, helping to prevent wear, pump ONLY what the engines CLEARANCES ALLOW, have a more constant pressure level, and they also don,t seem to understand that the hydrolic lifters in most engines have internal valves that limit the oil flow voluum, in almost every case where someome says the valve covers fill up at high RPMs, your talking to someone whos just repeating something they heard, or someone whos FAILED tO CORRECTLY PREP THE BLOCK AND/OR USE A WINDAGE SCREEN not someone thats actually tested the engine to see if what they are talking about is true

 

read this part of that big post above

 

now what does quite frequently happen 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............ 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

 

BTW WHILE WE ARE TALKING ABOUT OIL SYSTEMS, just some info, see these remote adapters, a fairly comon reason people install high voluum pumps is to use these remote adapters

 

 

 

well a fairly comon way to kill an engine is to INCORRECTLY install one of these remote filter adapter kits,

look at the top picture and keep in mind that those two connecting hoses COULD be flipped as to what end(in/out ) on the remote filters gets hooked to the bypass adapter (IN/OUT) ports, hook it up correctly and everything works just fine! but swap the two hoses on only one end and YOUR OIL PUMP tries to push OIL PAST the ANTI-DRAINBACK VALVES on the oil filters,(and most of the time is marginally successfull in that a trickle of oil does get to the bearings and rocker arms at idle) now at idle youll still get good oil pressure (about 15 lbs) but rev the engine and the highly restricted oil flow pressure goes up very slowly but the oil VOLUUM getting into the block is so low youll spin a bearing in about the first 20 minutes ( [color:"red"] and 99% of the time the guy that does this blames the guy who built his engine for putting it togeather WRONG when in fact the engine could have been PERFECT but with no oil reaching the bearings under load the engine is history within at best about an hours running time! [/color]

[Guest gbvol54]

Excellent short course on SBC lubrication. Thanks Grumpy.

[RTz]

You've got one more chance to explain your point with more detail, otherwise this off topic discussion gets deleted from Grumpys wonderful thread.

 

Sorry Paul, I'm pulling the E-brake on this one.

 

 

gocart98r, You've been PM'd

[Guest gocart98r]

You need to picture what is really going on using a free body diagram. Think about the force acting on the moon, as it spins around it wants to go outwards but is kept in by gravity. As is with the oil it wants to follow a tangential line on the crankshafts orbit and is only held in by a force and therefore not being pushed outwards, I understand what you mean by the oil pump exerting a force outwards but as with oil coming off its centripetal force. Ask an engineer, I'm only in training. And this whole thing is off topic but whatever its interesting I liked how my thinking thought when I was taught about it.

[BRAAP]

You need to picture what is really going on using a free body diagram. Think about the force acting on the moon, as it spins around it wants to go outwards but is kept in by gravity. As is with the oil it wants to follow a tangential line on the crankshafts orbit and is only held in by a force and therefore not being pushed outwards, I understand what you mean by the oil pump exerting a force outwards but as with oil coming off its centripetal force. Ask an engineer, I'm only in training. And this whole thing is off topic but whatever its interesting I liked how my thinking thought when I was taught about it.

 

 

The “pressure” results from the centripetal force which is the result of the bearing clearances only allowing “so” much oil to escape, vs how much oil is being fed to the bearings from the pump AND from being flung away from the crank centerline out to the rod journals due to CENTRIFUGAL force!

 

Centripetal is the inward force that resists the centrifugal OUTWARD force, Centripetal could also be the measurement of whatever is holding back the mass from the centrifugal force, i.e. pressure. Just as you described with the Moon, the Earths gravity is the centripetal force in that scenario holding the Moon in orbit, while the speed of the Moons orbit along with its mass is resisting the centripetal force, (dat dar be da centrifugal force), trying to fling the moon away from the Earth, in a straight line, yet the earths gravity isn’t allowing that. Same as in the oil galleys of the crankshaft.

 

 

At that, this is car guy stuff, not quantum physics. We are all accurately understanding what is taking place on the same level, regardless of the exact terminology. Grumpys post stands and will remain. Feel free to take this up with your professor/s.

 

 

[lsdengines]

Wow, that was some good reading. I agree that physics applies to all aspects of things mechanical, but there is a way to put it in car guy speak. I'm not calling car guys dumb, I have a degree in physics and nuclear engineering, but you will rarely hear me talk like it, it turns people off.

 

Not trying to debunk grumpy, everything he said was 100% correct, but the new rule for oil pressure(according to robert yates and the majority of the endurace racing world) is a minimum of 35psi, and 10 psi per 100hp. Which means any engine needs 35psi regardless, but a 500hp engine only needs 50 psi even at 8000rpms. Notice I said endurance, not drag racing or qualifying, this rule works well on the street as well. For drag racing, my old 522 ford only had 8 or 9 psi going through the traps, this would not work on the street.

 

I'm not going to go into all the specifics on everything else, grumpy did that very well. Stock pumps are almost always more than adequate for a street engine. Not high volume, not high pressure, stock replacement. combine the stock replacement pump with a hardened driveshaft and do some other oil control tricks(scraper,windage tray with drain holes or mesh, radius drain backs, etc), set bearing clearances, and run a thin oil, and you will have plenty of oil pressure without robbing the engine of power or causing spark scatter at higher revs.

 

As far as sucking the pan dry, your buddy either had sever drain back issues, or didn't have enough oil in the pan.

[dr_hunt]

Not trying to debunk grumpy, everything he said was 100% correct, but the new rule for oil pressure(according to robert yates and the majority of the endurace racing world) is a minimum of 35psi, and 10 psi per 100hp. Which means any engine needs 35psi regardless, but a 500hp engine only needs 50 psi even at 8000rpms. Notice I said endurance, not drag racing or qualifying, this rule works well on the street as well. For drag racing, my old 522 ford only had 8 or 9 psi going through the traps, this would not work on the street.

 

 

 

They run dry sump engines, yates is referring to dry sump systems. They run 700 to 800hp and are running 70 to 80psi hot oil pressure if you information is correct. A hot street motor making 500hp would then need 50psi hot oil pressure, not going to get that with a stock pump and the kind of bearing clearances necessary to make that live. On dry sump late model and sprint motors I always adjust the pressue to 80psi hot, which is easy to adjust on dry sump systems. Wet sump is a different story, shimming the pressure spring or changing springs is necessary which requires pan removal and sometimes engine removal to remove the pan.

 

Oil volume through a bearing clearance at a given pressure is x, that about doubles with every .001 additional clearance. So if you are running .0015 main and rod bearing clearance a stock pump is fine for 40psi. If your running .0025 main and rod bearing clearance, then it won't work very long, you need almost 2x, and your max oil pressure will be lucky to hit 35psi.

 

You can't just say stock pumps are great for stock or mild motors, stock pumps are fine for tight clearance (.00125 - .0015) engines at mild HP levels. Anything else (HP or clearance) requires more volume and pressure IMO, although they go hand in hand.

 

If you take your crank to joe blow crank grinder and he always grinds them on the loose side so he doesn't have comebacks, your going to have low oil pressure with a stock pump I don't care how much HP it puts out.

 

In a wet sump system pressure is governed by bearing clearance and pump displacement volume and pressure spring. If the displacement volume is stock and the bearing clearance loose, you will never achieve the pressure spring relief valve to open IMO. If you have a HV displacemet volume and tight clearance, then the pressure spring relief valve will be open pumping oil back into the pan and costing you HP and heating the oil IMO.

 

IMO the proper statement of oil pump selection should be based on bearing clearances and actually checking them on assembly of the engine. It's absolutely necessary IMO to dictate bearing clearance to the machine shop prior to machine work being performed. Oil pump selection is then based on proper oil system (pan, pickup, pump) parameters, engine HP and rpm.

 

Oil selection also plays a big part of things. IMO a 5w30 oil lubricates better and has less entrained air in an oil system than heavier oils. My preference though and therefore my opinion.

[lsdengines]

my 96 lt1 has the stock oil pump in it. Holds 25-30 psi at idle, dead on 65 at 7000 rpm's. Thats a mildly built(about 425fwhp) engine plus a 200 wet shot with 75k miles on it. That is also with 5-30 mobil1. The engine in reference was a small block chevy, in which case the stock pump is more than enough for his mild goals. I wasn't saying that my new turbo lt1 I am building would be fine with a box stock oil pump, but I will use a stock replacement pump and blueprint it to my likings. I also wasn't saying that if your 500hp engine is putting out 80psi that you need to take it apart and open up your clearances. I was stating that your 500hp engine turning 8k will be fine with 50psi.

I used to work for yates so yes I know that it was a dry sump. All I was trying to do was give a different perspective on this topic. To answer the origional question again, and to get to the ultimate point of it. Either pump would be fine for the 325-350hp range you were mentioning. On a small block chevy, the stock replacement pump will make plenty of pressure and volume without costing you the power of the hv/hp pump.