High Volume Oil Pumps - I hear many things..

[bubba-dough]

stomwalker you left off a good line at the end of the first article from Melling "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."
I run the hv Melling in my 347 with a canton 7 qt pan. Both of which were recommended by my builder. I will admit I know NOTHING about this subject though, just what I have read.

 

[Stormwalker]

Fixed it, good point. That article does make the argument that a HV oil pump is not really detrimental in any way.

 

[EMW150]

Well, I do remember hearing and reading about a temperature issue relating to the use of a high volume oil pump, but perhaps what I have heard is wrong (I am not being facetious here, I want to learn something out of this!). I looked up a couple of things and found a couple of interesting tidbits of knowledge. First, I found this:



Also, I found this tidbit of info too, which correlates with what I had presumed earlier:



So on one hand, I hear about wear and tear on the distributor/cam gears, and then I hear that it is not true, and I am also getting mixed messages about the temperature issue (which Daggar is adamant about not being an issue - and I see his points). Now I am starting to get confused.

Article sources:

http://www.melling.com/support/bulletins/bulletin-3rd.htm

http://www.aa1car.com/library/2004/ic110446.htm

Some of the facts posted in the articles are easily debatable. For example, about the dist. gears. Take an electric drill and prime your engine. When the pressure goes up the drill bears down and has a heck of a load on it. This is because when the pressure goes up, so does the resistance on the pump which is driving by, that's right, the distributor gear. It's fact that high oil pressure wears out distributor gears faster. Especially when you get into bronze gears for solid rollers.

The second article I agree with. When you add an oil cooler, you have to pump oil alot further out the the lines and through the cooler which should be compensated for with more volume.

 

[EMW150]

Another point I think Melling is missing, is yes, lifters limit oil to the top of the engine (to an extent) but it's based on the pump installed from the factory. A standard volume pump. Up the pressure, with the same clearances throughout the engine and it's going to pump alot more oil to the top end and your still relying on the stock drainback system. Alot of guys who run high pressure pumps for aggressive ramped high rpm applications use restricted pushrods to keep them from pumping too much oil to the top.

 

[Daggar]

About the only consistent downside to high volume or high pressure pumps is the additional HP they take to operate vs. the stock volume pump. They're also typically a bit more expensive and just plain old not required.

I wouldn't have any reservations about running a larger volume pump on an engine with 'loose' tolerances or a high mileage block that runs well even though the oil pressure might be under what is desired. I don't subscribe to the "suck the oil pan dry" theory either. I tend to think that if someone has experienced that condition that it was probably due to the oil level being low anyway.

 

[Daggar]

Another point I think Melling is missing, is yes, lifters limit oil to the top of the engine (to an extent) but it's based on the pump installed from the factory. A standard volume pump. Up the pressure, with the same clearances throughout the engine and it's going to pump alot more oil to the top end and your still relying on the stock drainback system. Alot of guys who run high pressure pumps for aggressive ramped high rpm applications use restricted pushrods to keep them from pumping too much oil to the top.

I get what you're saying here but lets not confuse high "volume" pumps with high "pressure" pumps.

 

[Black 93 Fox]

I put my motor together this last June/July I was going to put in a high volume pump but the machince shop asked right away if I have a 7quart oil pan and I replied no. Basicly what happens is on the top end when the motor is really spinning the high volume oil pump sucks the stock pan dry and you arent giving the motor all the oil pressure that it needs. Another reason is the oil return holes in the block need to be bigger so the oil can return faster to the pan which is the main reason why the higher volume pump sucks the pan dry. The reason the machince shop knew this was because many customers where having problems so they but a engine on a dyno with a oil pressure gauge mounted at a different location other then stock I dont remember exactly where and it showed the oil pressure dropping when the high rpms got reached. I always wondered why they made a 7quart pan now I know. Anyways I just put a stock replacement pump in and a stock oil pan everything works just fine. Also this machine shop isnt any just around the cornor place they build 1000hp plus engines, just thoght I would share my info.

 

[Daggar]

I put my motor together this last June/July I was going to put in a high volume pump but the machince shop asked right away if I have a 7quart oil pan and I replied no. Basicly what happens is on the top end when the motor is really spinning the high volume oil pump sucks the stock pan dry and you arent giving the motor all the oil pressure that it needs. Another reason is the oil return holes in the block need to be bigger so the oil can return faster to the pan which is the main reason why the higher volume pump sucks the pan dry. The reason the machince shop knew this was because many customers where having problems so they but a engine on a dyno with a oil pressure gauge mounted at a different location other then stock I dont remember exactly where and it showed the oil pressure dropping when the high rpms got reached. I always wondered why they made a 7quart pan now I know. Anyways I just put a stock replacement pump in and a stock oil pan everything works just fine. Also this machine shop isnt any just around the cornor place they build 1000hp plus engines, just thoght I would share my info.

This seems likely to be more true of a high "pressure" pump than a high "volume" pump. A high volume pump is not going to pump oil up through the engine much (if any) quicker than the stock pump will. The internal pressure bypass in the pump would not allow that.

Edit: You would also probably have to have some pretty loose bearing tolerances to allow enough volume through to make that happen as well.

 

[vristang]

subscribing so that I can respond when I get home.

 

[Daggar]

2. 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.

Let's not forget those pesky metering valves!

 

[txstang84]

the bit about engines on dynos...I recall seeing an article about this in a magazine (PHR, I believe)-basically what they mentioned was that on an engine dyno, the engine sits perfectly level...this is not so in a car. Most, if not all cars have the engine tilted slightly back, not to mention, under high acceleration, the oil will be forced back to your sump due to forward acceleration-hopefully keeping the pickup saturated with oil...so, on a dyno where there is no tilt, or forward motion, yes, it may suck the pan dry, but not near as likely when actually driving it...deceleration is another discussion all together...

 

[EMW150]

This seems likely to be more true of a high "pressure" pump than a high "volume" pump. A high volume pump is not going to pump oil up through the engine much (if any) quicker than the stock pump will. The internal pressure bypass in the pump would not allow that.

Edit: You would also probably have to have some pretty loose bearing tolerances to allow enough volume through to make that happen as well.

The high volume pumps I used in the past had stiff relief springs or not enough capacity which did not bypass for ****. Seeing 100 psi cold /80 plus driving, is not my idea of just a high volume / standard pressure pump. That was a FMS high volume pump. I've never used a Melling High Volume pump. Also bearing tolerances don't necessarily have anything to do with sucking the pan dry. The excess of what the bearing clearances don't take is sent to the top of the engine.

 

[Daggar]

The high volume pumps I used in the past had stiff relief springs which did not bypass for ****. Seeing 100 psi cold /80 plus driving, is not my idea of just a high volume / standard pressure pump. That was a FMS high volume pump. I've never used a Melling High Volume pump. Also bearing tolerances don't necessarily have anything to do with sucking the pan dry. The excess of what the bearing clearances don't take is sent to the top of the engine.

If you have a high volume pump with a sticky relief valve then it stands to reason that you could pump the pan dry. I could see that. What you said about bearing tolerances is true. It's the reason I posted the subsequent entry about the metering valves. Something (one way or another) with a CORRECTLY operating oil pump is going to slow that oil from coming out of the top of that engine like geiser. A high volume, high pressure pump might have that potential although I've never seen it happen first hand. It's always been one of those "my buddy" stories.

 

[EMW150]

If you have a high volume pump with a sticky relief valve then it stands to reason that you could pump the pan dry. I could see that. What you said about bearing tolerances is true. It's the reason I posted the subsequent entry about the metering valves. Something (one way or another) with a CORRECTLY operating oil pump is going to slow that oil from coming out of the top of that engine like geiser. A high volume, high pressure pump might have that potential although I've never seen it happen first hand. It's always been one of those "my buddy" stories.

You seem to be subscribing to the theory that a high volume pump should operate at the same pressure as a standard volume pump. Not true. I've seen it first hand in my engines over the years and working on many other engines. Race and Domestics. Also their's only one way to reduce the oil at the top end in a high volume / high pressure application and that is with a restriction installed either in the galley or with restricted pushrods.

 

[Daggar]

You seem to be subscribing to the theory that a high volume pump should operate at the same pressure as a standard volume pump. Not true. I've seen it first hand in my engines over the years and working on many other engines. Race and Domestics. Also their's only one way to reduce the oil at the top end in a high volume / high pressure application and that is with a restriction installed either in the galley or with restricted pushrods.

I acknowledge that the addition volume produced by a high volume pump might slightly raise pressure as a side effect but not by a significant amount. Not if the internal pressure relief valve is desigend to operate at stock pressures. It can really only increase to the point that the ball in the valve unseats.

 

[EMW150]

I acknowledge that the addition volume produced by a high volume pump might slightly raise pressure as a side effect but not by a significant amount. Not if the internal pressure relief valve is desigend to operate at stock pressures. It can really only increase to the point that the ball in the valve unseats.

I think what usually happens is, the relief passage can't take the volume of oil that it would need to bypass and stay at standard pressures. The only other thing it can do is run at a higher pressure and send the oil through the engine. I looked up the part # of the last FMS high volume pump I used in my engine. FMS-6600 D2. That is a Ford Motorsport high volume / standard pressure pump yet it ran at 80 plus psi hot and over 100 cold. How else would you explain it?

 

[Daggar]

I think what usually happens is, the relief passage can't take the volume of oil that it would need to bypass and stay at standard pressures. The only other thing it can do is run at a higher pressure and send the oil through the engine. I looked up the part # of the last FMS high volume pump I used in my engine. FMS-6600 D2. That is a Ford Motorsport high volume / standard pressure pump yet it ran at 80 plus psi hot and over 100 cold. How else would you explain it?

I think that you are correct about the relief passage being a contributing cause but at the same time, I submit that if the tolerances in the motor were to spec and the pump were providing adequate volume for the combination that adding a high volume pump shouldn't show much of an increase. I imagine that though, that if tolerances were loose and the stock volume pump were unable to provide the volume necessary to even approach the valve relief point that you most certanly would see an increase up to the point where the valve was able to be unseated.

Going back to relief passages: I believe (although I'm not sure) that the valve (in a stock pressure pump) is set to around 60 psi. Anything over that would most certainly have to be the result of oil viscosity being pushed through x sized port. It stands to reason since changes in the weight of oil would have a similar effect.

I think I've gotten a bit off track though. The question that enters my head is whether or not the pump would be able to force enough fluid through all the nooks and crannies fast enough to beat the oil coming back down into the pan.

 

[EMW150]

the bit about engines on dynos...I recall seeing an article about this in a magazine (PHR, I believe)-basically what they mentioned was that on an engine dyno, the engine sits perfectly level...this is not so in a car. Most, if not all cars have the engine tilted slightly back, not to mention, under high acceleration, the oil will be forced back to your sump due to forward acceleration-hopefully keeping the pickup saturated with oil...so, on a dyno where there is no tilt, or forward motion, yes, it may suck the pan dry, but not near as likely when actually driving it...deceleration is another discussion all together...

Keep in mind also, there are 2 drainback holes in each Ford head. One in the front, one in the back. If you're launching the car on slicks and pulling some Gs, you're only using the rear 2 drainbacks because the oil is going to be running to the back. They're not very big holes and I can see how it could easily happen with a stock volume pan.

 

[Daggar]

I've gotta run but should be back on again later tonight. Great thread though. I'll try and catch up with you guy again on this later.

 

[EMW150]

I think that you are correct about the relief passage being a contributing cause but at the same time, I submit that if the tolerances in the motor were to spec and the pump were providing adequate volume for the combination that adding a high volume pump shouldn't show much of an increase. I imagine that though, that if tolerances were loose and the stock volume pump were unable to provide the volume necessary to even approach the valve relief point that you most certanly would see an increase up to the point where the valve was able to be unseated.

Going back to relief passages: I believe (although I'm not sure) that the valve (in a stock pressure pump) is set to around 60 psi. Anything over that would most certainly have to be the result of oil viscosity being pushed through x sized port. It stands to reason since changes in the weight of oil would have a similar effect.

You're missing the point I was making. Let's say you have a high volume oil pump. Relief spring at 60 psi like you said. Depending on the rpms, it's going to send X amount of oil somewhere. Lets say it's sending 500 CCs per minute (just pulled out of the sky) So let's say the relief valve will only flow 50 CCs and the engine load will only take 200 CCs to maintain 60 psi oil pressure. You got 250 CCs that won't relief because the relief valve is already flowing a full 50 CCs because the valve is fully open. The only thing that can happen is the pressure will spike and the oil will go to the source of least resistance. The source of least resistance is the top end... to the rockers. The numbers I used are for example only, but do you get my point?