High vol oil pump...a waste of time/$$

[dave571]

I recently read an article in hot rod, that discussed how racers lower the flow output of thier oil pumps, so they are not as much of a drag on the engine.

I found this quite interesting, because a lot of people include a high volume oil pump in the rebuild of thier performance motor.
It would seem a high volume oil pump would be the opposite of what the hot rod article was getting at.

I have said myself, that a HVOP is properly used in and engine with larger brg clearances to restore pressure, not in a "tightly" rebuilt motor.

I have tested the theory on my 400.

When I assembled it, I measured the clearances at .0025 on both the rods and the mains. This is the upper end of allowable specifications. Since it's the upper end, I used a HVOP. I found the engine makes a lot of oil pressure. 90 lbs at 3000 rpm hot. nearly 50lbs at idle hot(checked with a mechanical gauge). When I started it cold yesterday(-10c), it pushed the pressure off of the electric gauge(100lbs) at idle.

After warm up ,I drove it to the shop, and installed a regular volume oil pump. There is a visable difference in the two, as the HVOP is about 3/16" thicker in the housing. The pump itself is bigger so it pumps more oil.

After installing the standard pump I still have 75-80 lbs cruising at 3000 rpm, and a more reasonable 35lbs at idle hot. Lot's of oil pressure.

It would seem that the HVOP was a complete waste of time and money. If anything, there is a good potential for engine damage with the extreme pressures it produced.

I would think the affects would be even more dramatic in a engine that is closer to .0015 clearance on the bearings.

Just thought I'd share that with you guys. It may be usefull for those of you who are assembling motors now, or feel that thier oil pressure is too high, while running a HVOP.

[lenweiler]

I believe that you were given a hi vol.-hi pressure oil pump which is standard equipment when ordering your type of pump.
The pump rotor is lengthened to give the extra volume and I guess the manufacturer decides that everyone wants the extra pressure so they add the stiffer relief spring.
Therefore, if you want the lesser pressure just replace the spring with the appropriate one that you want. Leave the volume alone.
Signed, UA Fitter.

[John Kunkel]

Dave's experience is not universal, I've seen plenty of instances where oil pressure drops off dramatically at high temperatures when the oil is hot.
Also, the size of the inlet affects the efficiency of the pump. In the case of the BB Mopar, if the 3/8" pickup is retained, the HV pump won't show much difference over the standard pump.

[dave571]

Lenweiler, The pressure is a function of volume. The more volume pushed through the brg clearances, the more pressure required to do so. When the lighter pressure relief spring is used, the oil is not pushed into the engine(it's dumped back to the pickup side of the pump/pan when the pressure is too high) Less volume of oil is pushed in so less pressure is the result. If this is the case, then why use the HVOP in the first place? What is the point, if the oil isn't actually being pushed into the engine brgs, just back into the input tube?

As John pointed out, there are instances where there are dramatic differences with a hvop. I have seen in brand X engines where an engine that would be condemned as no good due to low oil pressure, has the pressure restored by using an HVOP. I have seen flow rate charts on oil, relating to brg clearance. It goes up Geometrically with clearance. ie: a clearance of .004 flows about 4(or more) times as much oil as one of .002(not twice as much) Hence the reason why engines go down hill so fast, pressure drops off fast, when clearances get beyond specifications.

I'm not saying a HVOP is useless. It does a great job of protecting engines with higher clearances. Got low hot pressure in your engine with 200 000miles? Still makes good power and don't want to do a rebuild? Get a HVOP.

I'm simply using my experience as an example of why a rebuilt engine does not require an HVOP. The relief spring modifications are simply reducing the pressure by reducing the volume. Skip the modifications and use the standard oil pump. Same volume will be pumped into the engine, pressure will be good, loss of power will be less.

[George G. Leverette]

This is quite confusing, a high volume oil pump will flow more oil at the same pressure as the standard pump, this will ensure adequate oil is available for lubrication with increased clearances. A high pressure oil pump will produce higher pressures at the same volume. Using a larger rotor and stiffer spring will produce more pressure in a high volume oil pump. Because the engine requires either increased volume or pressure using them in combination could cause problems, such as the oil not performing it's cooling function, especially with excessive pressures. The user should decide what is required and apply it. As a general rule high volume is ok in most applications, high pressures can cause problems in moderate (400HP or less) performing engines.

[dave571]

George, I think you're on the right track, but I'm a little confused by your post.

The high volume pump flows more oil, which benefits higher clearance engines by maintaining oil pressure. Absolutely.

To say a HVOP flows the more volume, at the same pressure is a little false.(not trying to start something with you george, just trying to get where your coming from)

The pressure is the result of the volume of oil being pushed through the clearances of the engine. The clearances are a restriction to oil flow. If flow increases, then pressure must as well(in the same engine/restriction) You can't have more oil flow at the same pressure, in the same engine.

What I'm getting at, with this discussion thread, is that a newly machined engine has very tight clearances. Oil pressure is easily maintained with a standard pump.

George, that's very interesting about oil losing it's cooling ability at high pressure. Perhaps that's part of the reason I had overheat issues with the van this year.

[pishta]

Waste of money. You wanna pump 5 quarts into your heads before it has time to drain back and starve your bearings? You have 85 PSI to your bearings, what are you trying to do, make the crank float? That is alot of drag on your motor.

[phoenix]

Great discussion, however, lets throw a curve to the thought process relative to the controversy. Thus far, no-one has mentioned the effect of rod SIDE CLEARANCE on their journals in a given engine, and it's effect on oil pressure leakage, as opposed to a strictly vertical bearing clrc issue. While we're talking about vertical clrc also, lets not forget that said clrc.'s are a product of the intended application of the engine / intended RPM
On a relatively "stock" rebuild, 6000 rpm and lower, @ 10:1 C.R., where the crank throw sides (above the rolled fillet), haven't been butchered by a bunyak crankgrinder, then .0025" vertical is probably ideal for a stock volume pump. Try the same stuff on a motor with excessive throw clrc. sideways ( .040) and the pressure hot might not be happy at idle, ditto the oil control rings. Lets also remember that our beloved mopar piston pins love to get they're oil from that groove in the rod cap lining up with the journal pressure, and the resulting "squirt" they get along with the crank throw-off.
Not trying to confuse the issue here, just attempting to point out that there are other factors involved to be considered. It's not just a simple "H V pumps are a waste of money" argument
"p" eccentricity Brg.'s or "H"??
Full or partial groove mains??
Restricted or non- res #4 cam brg.??
Wt.of oil to be used??? Synthetics??? operating temp"s ??
I best quit now, talk to your builder/machinist as per your application.

[Billydelrio]

Looks to me that everyone is coming to the same point from a different angle. Use what your engine requires.

My explanation for the use of a HVOP is simply that it can maintain a given pressure for a wider range of engine oil demands. A stock pump will drop indicated pressure because it can't pump the volume required to keep the pressure up.

What pressure do you want is the question. I would use the HVOP and check/adjust the maximum pressure before I install the pump. How?
1. Bolt the pump to a main cap clamped in a vise.
2. Attach a pressure gauge to main cap.
3. Hang a hose from the inlet into a bucket of oil
4. Drive the pump with a drill motor
5. Adjust pressure with springs and/or shims
6. Clean up mess.

Once you know this particular pump's maximum pressure, the actual pressure on the engine will help you determine the engines "condition" or "oil demand" or whatever you might be interested in.

Billy

[biggerhammer]

the problem I see with most high perf. engines is too much side clearance like was mentioned earlier in the posts. it only takes .0025" too much clearance to REDUCE the oil pressure by 10+ psi. there are alternatives to pressure/volume problems. if you want a lot of pressure only, then replace the spring in the pump bleed valve with a stiffer one, if you want to use a high volume, but not starve the bottom, use restrictors in the lifter galleys, or you can use pipe-stem cleaners in the hollow push rods, but most chrysler push rods are solid.
on some of the small block chevies, you can use a big block oil pump, which provides 36% more volume but uses 5-7 hp less to drive them. you might see if there is something comparable for the d-c engines. I will experiment with it myself soon.
whatever you do DON'T STARVE THE BOTTOM END!!

[RALPH]

with all this oil pump talk, i was just curious if anyone knows at what rpm is the stock pump good to. i've heard 7000 rpm that sounds a bit high to me. whats the word on the matter.

[6 packin]

pressure is inversly purportional to the square root of flow.

Its my experiance that in stock or street applications a high flow oil pump is not needed and if used full grove main bearings are needed.

There seems to be some confusion of oil pumps here.......

there is a diff between high flow and high pressure oil pumps.

I do not reccomend a high pressure oil pump, only high volume.

also being what i said pressure is proportanial to velocity. which in laymens terms what determins pressure.

[deadhorse66]

Defenition of pressure:

The resistance to liquid flow measured in wieght per area. Pressure has an indirect relationship to flow and a direct relationship to resistance. As flow increases without changing any other factor (in a system with no relief), pressure will increase as will velocity after the restriction. At the same time, if resistance is increased without changing volume, then pressure will increase (velocity before the restriction will decrease--restriction being the bearing clearance).

DIRECT RELATIONSHIP INVERSE RELATIONSHIP -pressure & resistance -pressure & velocity before restriction
-pressure & volume
-pressure & velocity after restriction

Oil volume never hurt anything, but there can be unwanted side effects (just thought I would agree with 6packin and maybe make it a little easier to understand). High oil pressure which results from a high volume pump on engines clearanced for standard pumps causes an increased load on the parts that drive the pump which robs horsepower, increased crankcase windage which results from the violent spraying of the oil due to the increased pressure also robs horsepower, oil can collect inside valve covers preventing oil from returning to the sump and therefore can cause starvation and cavitation problems, oil dropping onto the crank can increase windage further and can also inhibit crankshaft inertia, and oil control rings can be overloaded. In a perfect world we would all have dry sump oiling, but that's just not going to happen. Like phoenix says, if you have high rod side clearances and "loose" vertical oil clearances such as encountered in an endurance or all out high rpm race engine, then high volume is needed to effectively spray the oil onto the splash lubricated parts (wrist pins, cylinder walls, etc). In reality, we (for the most part) cannot afford an $8,000 dry sump system (which by the way are very high volume) nor do we really require one. Generally speaking, unless you are planning on a "loose" engine or are replacing a standard volume pump on an engine with worn bearings, HV pumps are overkill. Again, as phoenix says, it depends on the purpose of the build, application, other oiling system mods, budget, etc. and by all means CONSULT THE BUILDER!

[deadhorse66]

Okay, that didn't work like I had planned, but what I was trying to say was that pressure, velocity after the restriction, and volume have a direct relationship. Pressure and velocity before the restriction have an indirect relationship.

[lenweiler]

Dddddddddddddddddddo what ever you think. Geez!

[Bigfoot]

I know when we installed a HVOP in my 1/2 ton it blew the rear seal out as soon as I started it up, what a pain. I remember reading a high performance book a couple of weeks ago and for drag racing the author suggested to use only enough oil to show "ADD" on the dipstick anything more was waisting horsepower. He also added that you have to be checking the dipstick all the time because of the lowered oil level so obviously he didn't recommend the HVOP.

[sanborn]

There is a lot of misunderstanding about High Pressure and High Volume oil pumps. Let me see if I can help-Some of the examples I use probably don't apply to you but they are used to explain a point.

An engine only needs enough oil to lubricate the moving parts. Along the way, the oil is also used to lubricate cylinger wall, piston pins,timing chain, etc. Any excess oil pumped and compressed is wasteful and builds up oil temperature.

A stock clearance engine, .002" main, .0015" rods, .006" rod side clearance, generally only needs a standard pump. High pressure is only needed at higher RPMs to maintain the oil "film" between moving parts; remember the old "rule of thumb"-10 lbs. of pressure per 1000RPM. It is a pretty good "rule of thumb".

It gets more involved with high performance engines with increased clearances, especially rod side clearance. A good "rule of thumb" for race bearing clearances is .001" per 1" of diameter-said another way, SB main bearings need .0025" and rods need .0021". Mopars don't generally need as much side clearance as GMs due to the design of the stock rod. Aftermarket rods need more side clearance in order to get enough oil on the cylinder walls-but .012" to .014" is usually plenty. Most race SBs don't really need a high volume pump(if clearances are done properly) if the RPMS are kept at 7000 or below. But your do need higher pressure but a stiffer bypass spring will usually do the job.

Where do you need higher volume? For "looser" engines either through wear or looser clearances. Or where additional oil is needed for other things-like valve spring spraying, camshaft lobe oiling or timing gear oiling. These additional things are small by themselves but taken together do add up. And really serious race engines usually use even more side clearance-up to .020". And at higher RPMs(above 8000) pumping losses do get great.

Why not use a High Pressure/ High Volume pump in everything? Because excess oil pressure or volume will wear your bearings out, put more strain on the oil pump drive shaft and overheat the oil. How does it overheat the oil? When oil is compressed, heat is generated by the compression. If more is compressed than needed, it is bypassed through the pump to the inlet side again. Constant bypassing gets the oil really hot and can lead to oil breakdown and bearing failure.

Let me give an example of oil pressure /volume management-it sort of applies here and sort of doesn't. But I find it interesting.

Nascar used to use qualifying engines-until this year. These qualifying engines were only designed to run 2-3 laps under full power and couldn't run a full race. What was so different? Not all but a big part was the oiling. They would use 5 stage dry sump pumps, one thin oil pressure section and four wide suction sections. The thin pressure section would not produce much volume and were set for only 30PSI of pressure. The wide suction sections would produce a vacuum in the engine of 12" of water. The high vacuum kept all excess oil off the rotating parts for less drag. Main bearing clearances were as tight as .0015" and rods were .001", side clearance was only .008"-just enough to maintain a ring seal-no more. 10 weight oil was standard-some teams used 5 weight. To heck with oiling the springs and the camshaft only had minimal oiling. What did all this produce? About an extra 7-10HP. It was worth it to them-but the engine wouldn't last long and obviously had to be "freshened" after each qualifying attempt.

Hope this explaination helped-but if it didn't -what the heck- lighting hit my dish last night and don't have the tube to watch and I didn't want to work in the shop tonight-so I got on here to bother yall.