High Volume Oil Pumps - I hear many things..

[Daggar]

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?

Yeah... I get your point. Your theoretical oil pump is a MONSTER! lol

No really, I DO get what you're saying. Provided that the oil pump was a positive displacement pump and the path of least resistance was the top of the motor (this is assuming that the check valve is maxed out) then the pressure would rise until the capacity of the pump could no longer overtake the back pressure or supply any additional volume at whatever pressure it peaked at.

The thought that comes to mind though is first, (like I said above) that's one hell of a pump. We're talking about a pump that would seem to have been designed to pump more oil than our theoretic engine would ever have need for. Maybe a big block pump in a small block motor. Something else that comes to mind in this scenario is that this overly large pump is using horsepower that would be better spent at the flywheel. The last thing, is that if you're supplying those kinds of severely elevated pressures and volume that you're also running the risk of breaking the oil pump shaft or spinning or stripping the gears.

From what I've read, high volume, stock pressure pumps are designed to provide between 10% and 20% more volume than the stock piece. Assuming that some of that volume is consumed by the oil paths (I'll assume half) and some consumed by fighting against whatever rise in pressure you DO see then the rest would be your net result in higher pressure reading. If normal pressure for a combination is 60 psi at operating temp and 4000 RPM and you're seeing 80 or more then I'd say the pump was too big for the application. That's HP out the window. Not to mention wear and tear on the rotating parts. On more than one occation, I've seen reference to NASCAR oil pressures hovering about 40 psi all day long.

I'm sort of lost as to how this part of the discussion ended up so detailed. Granted that a higher volume oil pump would produce some pressure elevation so long as the capacity of the motor to make a path for that oil got closer to reaching capacity but it's also that very capacity limit that would keep the pump from feeding the motor to the point where the pickup ran dry. See what I'm saying?

 

[vristang]

I have a high mileage 5.0, probably close to 200,000 miles, but still runs strong. It just had the oil pump seize, and I replaced it with the high-volume pump, as I figured the motor is loose enough to handle the extra flow without high pressure issues.

PSI Numbers:

30 - 35 cold
50-55 at speed cold
45-50 at speed warm
25-30 idle warm

I hear from many about staying away from the high volume pumps. Is it more of an issue for new tight motors that cannot handle the increased flow?

BTW, as soon as the pressure dropped, I turned off the motor. No new noises since replacing the pump & shaft.

Which pump did you get? I have run 2 Melling HV pumps in 351w with no rise in pressure. Both were fresh motors.

As also stated by Daggar, the disadvantage is the power lost by pumping excess oil through the releif valve. I figured this concern was similar to going in for Heart surgery and asking the doctor how heavy the new heart was, because you were trying to lose weight. Take the hit and make the power up somehwere else.

There has been alot of discussion on running a stock pan dry. I dont' see how the drain back of oil from the top end could be that resrictive. Unless there is an obstruction (piece of gasket maybe?) the drain holes should be quite sufficient. I have heard of small block chevys needing restrictors in the valvetrain, but never for a windsor. Even in the case of the chevy though the valve train restrictor was used to increase flow to the bottom end, not to avoid oil getting stuck above the heads. I just don't see how an HV pump could cause this without there being some other problem with the motor.

As for HV pumps producing greater pressure, I would supect that the pump was assembled incorrectly. All too often people assume that a new part is properly built. Although it is not common, I think this is the most likely explanation (barring obvious things like a chunk of silicone plugging up an oil passage) for the problems EMW150 has been describing.

chepsk8 - The only real downside I can see to running an HV pump in your motor is a possible decrease in efficiency/peak power due to the excess flow. Please let us know what your new oil pressures are like.
jason

 

[bubba-dough]

Ok. I have tried my best to keep up even though I took about 9 hours off for work. I see and understand both of sides of what is going on. But back to what I read 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."

If saying this is untrue, how can Melling say this. I would be inclined to believe them because they have the engine and engineering backing to claim this. If for instance they are wrong why
hasn't anyone sued the s*** out of them if they are wrong.

Please don't take this wrong, I am enjoying this thread because I truly would like to learn more on this. Like I stated before I didn't build my 347 but my builder recommended the hv pump (I bought Melling) and a 7 qt. pan (I got a Canton). BTW my oil pressure is fine through-out operating temp.

 

[EMW150]

Yeah... I get your point. Your theoretical oil pump is a MONSTER! lol

No really, I DO get what you're saying. Provided that the oil pump was a positive displacement pump and the path of least resistance was the top of the motor (this is assuming that the check valve is maxed out) then the pressure would rise until the capacity of the pump could no longer overtake the back pressure or supply any additional volume at whatever pressure it peaked at.

The thought that comes to mind though is first, (like I said above) that's one hell of a pump. We're talking about a pump that would seem to have been designed to pump more oil than our theoretic engine would ever have need for. Maybe a big block pump in a small block motor. Something else that comes to mind in this scenario is that this overly large pump is using horsepower that would be better spent at the flywheel. The last thing, is that if you're supplying those kinds of severely elevated pressures and volume that you're also running the risk of breaking the oil pump shaft or spinning or stripping the gears.

From what I've read, high volume, stock pressure pumps are designed to provide between 10% and 20% more volume than the stock piece. Assuming that some of that volume is consumed by the oil paths (I'll assume half) and some consumed by fighting against whatever rise in pressure you DO see then the rest would be your net result in higher pressure reading. If normal pressure for a combination is 60 psi at operating temp and 4000 RPM and you're seeing 80 or more then I'd say the pump was too big for the application. That's HP out the window. Not to mention wear and tear on the rotating parts. On more than one occation, I've seen reference to NASCAR oil pressures hovering about 40 psi all day long.

I'm sort of lost as to how this part of the discussion ended up so detailed. Granted that a higher volume oil pump would produce some pressure elevation so long as the capacity of the motor to make a path for that oil got closer to reaching capacity but it's also that very capacity limit that would keep the pump from feeding the motor to the point where the pickup ran dry. See what I'm saying?

LOL , I should've put a better disclaimer with my example. I exaggerated the figures to make sure my point was clear.

vristang: Go to the Corral and do a search on high volume oil pumps and see how many psi the guys are seeing on their gauges. Now I'm talking 302 blocks - 351s are completely different. There are a few with wide bearing clearances that see lower pressures but most are seeing 80plus psi hot. Now these are supposed to be standard pressure pumps. You tell me why they won't bypass other than the bypass is maxed out. I can tell you with 100 percent confidence that my pump was correctly installed, I've been building engines and racing for alot of years. The pump was too big. I think a standard volume pump in a 302 with standard clearances is already bypassing oil alot of the time. Now a high volume pump still has the same size relief and you're adding 25 percent more volume. All it can do is max the bypass and the remaining oil volume is going to up the pressure.

 

[rd]

Good info here.

Both of my engines have Melling HV pumps.

The 68 block has 97k miles and has run fine since 1986 with the pump and a stock Mustang pan. I use 10-w-40 in it, and spin it to 6k at the track.

The rebuilt 79 motor, that I built in 99, in my 79 (not the orig) apparently had tighter clearances, per my plastigage checks, and with the HV pump, and 10-w-30 oil, runs much higher pressures. It will peg the stock gage on cold weather starts.

Next time, I think I will stay with a stock pump.

 

[EMW150]

Granted that a higher volume oil pump would produce some pressure elevation so long as the capacity of the motor to make a path for that oil got closer to reaching capacity but it's also that very capacity limit that would keep the pump from feeding the motor to the point where the pickup ran dry. See what I'm saying?

Think about that. The oil is being sent to the top under high pressure, it's only gravity sending it back. Anything sent to the rockers comes back to the pan (gravity fed) through two 5/16" holes since under accelleration at a drag strip the oil is going to flow to the back of the valve covers and the front two drains will be pretty much useless.

 

[chepsk8]

I chose the HV pump as my motor had lower oil pressure due to age & mileage. With the standard pump, I was getting warm PSI only in the 40's. No I am at 50-55, so in my case, the HV pump is just keeping more oil in the motor. When I build a new motor, then I will have to think twice.

Lots of good info here!

 

[Daggar]

Think about that. The oil is being sent to the top under high pressure, it's only gravity sending it back. Anything sent to the rockers comes back to the pan (gravity fed) through two 5/16" holes since under accelleration at a drag strip the oil is going to flow to the back of the valve covers and the front two drains will be pretty much useless.

Exactly, you're talking about displacing more than a gallon of oil before what you sent to the top of the block 'first' gets back to the oil pan. Without some other restriction in the oil return path, that is just not likely to happen. Keep in mind that if the oil pickup is properly installed that it sits just 3/8s to a half inch from the bottom of the pan. In th e HV pumps that you've run.... have you ever run one dry?

 

[EMW150]

Exactly, you're talking about displacing more than a gallon of oil before what you sent to the top of the block 'first' gets back to the oil pan. Without some other restriction in the oil return path, that is just not likely to happen. Keep in mind that if the oil pickup is properly installed that it sits just 3/8s to a half inch from the bottom of the pan. In th e HV pumps that you've run.... have you ever run one dry?

I think it can happen. Consider also that the pickup is at about the center of the rear sump. The engine is already tilted back the way it's mounted in the car and now the car is setting down pulling some G's going down the track forcing the oil farther to the back of the pan. I've never ran one dry but I've never ran one with a stock pan either. I do know it happens though.

 

[bluevenom867]

This is still going on ?

J/K,so what more do we need answered, hum?

 

[Daggar]

This is still going on ?

J/K,so what more do we need answered, hum?

I'm not sure. I think we've beaten this topic to its relative death.