Hi Flow oil pump?

I'm doing the pan, RMS, and OFA adapter seals, and figured since I'm there I might as well stick in a new pump. Don't really know if I need one really but since I'm in there...


I've read to get a High Volume pump instead of a regular one.
Anyone have suggestions for a new one I could get at a parts store?

I was also wondering if I'll notice any increase in oil pressure with a Hi Volume pump.
I'm running 40+ to 48 on highway.
Warm idle is 37, hot around 22-28.

May be pertinent and why I wonder about the current pump:

When I got the Jeep it never went below 40 hot or cold. Ran mostly around 50-60+ on highway and would drop down to 40-45 after an hour or so on road. Satyed there hot idle too.
I did switch from Fram Tough Gaurd to Purolator filters.
A while back I switched to 5w30MaxLife (synth blend) once, 10w40 (dino) then back to 10w30MaxLife ever since just seeing if a different visc. would help my lifter tick at start up.
Seafoam and a TB scrubbing cured that though, so I went back to 10w30MaxLife.
Pressure change occured after the switches.
Could I have just cleared out crud (build up of what not from using same brand a lot i.e. detergents etc.) around the sensor that was giviing a false high?

Either way I need a recommendation for a good replacement.

I should be able to go full synthetic now without worry!

Napa has a good HV oil pump for $1 more than a standard pump, and it comes with a new pick-up tube and screen, a $36 value. Your oil pressure will not necessarily be higher as it's a HIGH VOLUME oil pump, not a high pressure pump. My 90 MJ runs the same oil pressure without an HV pump as my 88 XJ does with one.

I would just run a stock pump in it. High Volume pumps move more total oil so if you wheel and are off camber you run the risk of starving the oiling system and causing engine damage faster. Back when I was in college I posed a similar question to my engine machining professor and he also said that a stock pump is more than enough for a stock engine. You also have to take into consideration that your moving more total oil up into the top of the engine and if you have a high mileage motor the valve seals and rings may not be up to the task of dealing with all the extra oil you are now introducing into those areas.

If your looking to "clean" the oiling system try ATF. Around a 1/2 quart before an oil change helps break up deposits. It also works to fix the ping that the older 4.2 and 4.0's had. If you get them hot and suck it thru a vaccum line it breaks the carbon build up apart on the valves and piston faces.

wheeling365 said:

I would just run a stock pump in it. High Volume pumps move more total oil so if you wheel and are off camber you run the risk of starving the oiling system and causing engine damage faster. Back when I was in college I posed a similar question to my engine machining professor and he also said that a stock pump is more than enough for a stock engine. You also have to take into consideration that your moving more total oil up into the top of the engine and if you have a high mileage motor the valve seals and rings may not be up to the task of dealing with all the extra oil you are now introducing into those areas.

If your looking to "clean" the oiling system try ATF. Around a 1/2 quart before an oil change helps break up deposits. It also works to fix the ping that the older 4.2 and 4.0's had. If you get them hot and suck it thru a vaccum line it breaks the carbon build up apart on the valves and piston faces.

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Rings could care less about the volume of oil that's traveling through the oil galleries and valve seals don't mind being splashed with extra oil. No oil pump is gonna pump a crankcase dry like you're describing. Tell Professor Bozo that he should go get some hands on experience and quit dispensing hypothetical BS to his students.

A stock flow rate pump will be fine unless you are planning to add an engine oil cooler. Then the HV pump is the way to go.

Based upon your current pressures, I do not see any need to replace the pump...

My opinion based on 50 years experience.

cruiser54 said:

Rings could care less about the volume of oil that's traveling through the oil galleries and valve seals don't mind being splashed with extra oil. No oil pump is gonna pump a crankcase dry like you're describing. Tell Professor Bozo that he should go get some hands on experience and quit dispensing hypothetical BS to his students.

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Well I'm so glad you know everything about an engine. :laugh3:

Last I checked if you move more oil by volume thru the system that means that there is less in the pan as a reserve. I never said that it was going to pump it dry but that the possibility was better than with a stock pump. It would be even greater with a high mileage motor that has sludge and deposits built up in the oil return passages which would slow the drain back time to the pan.

It also means that if there is more oil in the head that the valve seals are trying to deal with more if it and can start to leak. It also can increase the chance that the PVC system gets a shot of oil sucked into it.

More oil moving around inside the engine also means that more will find its way on to the piston walls which means that the oil rings will have to work harder to deal with the increased volume.

Seems pretty common sense to me. Maybe that professor should go back to building drag motors.......

wheeling365 said:

Well I'm so glad you know everything about an engine. :laugh3:

Last I checked if you move more oil by volume thru the system that means that there is less in the pan as a reserve. I never said that it was going to pump it dry but that the possibility was better than with a stock pump. It would be even greater with a high mileage motor that has sludge and deposits built up in the oil return passages which would slow the drain back time to the pan.

It also means that if there is more oil in the head that the valve seals are trying to deal with more if it and can start to leak. It also can increase the chance that the PVC system gets a shot of oil sucked into it.

More oil moving around inside the engine also means that more will find its way on to the piston walls which means that the oil rings will have to work harder to deal with the increased volume.

Seems pretty common sense to me. Maybe that professor should go back to building drag motors.......

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If you have enough oil building up in the head to cause a problem with the valve seals, then you have other issues to deal with. And there is going to be oil on the cylinder walls (didn't know that pistons had walls?) no matter what and a high volume pump is not going to make a difference in how much is splashed on the walls. This comes from 25 years of building engines for our desert racers.

I had to bang out the 96 oilpan to make room for the lower hi-flow pickup. . .

gradon said:

I had to bang out the 96 oilpan to make room for the lower hi-flow pickup. . .

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THANK YOU!!! That's exactly what I was looking for gradon!
I had a feeling about how it mounted lowr being an issue.
Regular it is.

Soooooo NAPA has one by Sealed Power for 82.49

Shuck's has one by Melling for 70.99 (I seem to recall someone on here recommending this but maybe saying NOT to get it too. Anyone?)

Baxter's has one by Sealed Power for 132.99. The SAME one as NAPA
they said the hi volume one is actually cheaper.
:soapbox:I love Baxter's but that HUGE price dif makes me question ever calling them again. rant off

So it looks like Sealed Power or Melling .

Whatcha think?

wheeling365 said:

Well I'm so glad you know everything about an engine. :laugh3:

Last I checked if you move more oil by volume thru the system that means that there is less in the pan as a reserve. I never said that it was going to pump it dry but that the possibility was better than with a stock pump. It would be even greater with a high mileage motor that has sludge and deposits built up in the oil return passages which would slow the drain back time to the pan.

It also means that if there is more oil in the head that the valve seals are trying to deal with more if it and can start to leak. It also can increase the chance that the PVC system gets a shot of oil sucked into it.

More oil moving around inside the engine also means that more will find its way on to the piston walls which means that the oil rings will have to work harder to deal with the increased volume.

Seems pretty common sense to me. Maybe that professor should go back to building drag motors.......

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Ever think that maybe I knew about it because I just did it on a 170,000 mile motor with no ill effects?
The volume isn't that much greater. It's about 20% max. You and the professor need to get together for a cup of Starbucks and discuss more theories that you have no direct experience with.

solomon7 said:

THANK YOU!!! That's exactly what I was looking for gradon!
I had a feeling about how it mounted lowr being an issue.
Regular it is.

Soooooo NAPA has one by Sealed Power for 82.49

Shuck's has one by Melling for 70.99 (I seem to recall someone on here recommending this but maybe saying NOT to get it too. Anyone?)

Baxter's has one by Sealed Power for 132.99. The SAME one as NAPA
they said the hi volume one is actually cheaper.
:soapbox:I love Baxter's but that HUGE price dif makes me question ever calling them again. rant off

So it looks like Sealed Power or Melling .

Whatcha think?

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Melling is a well known and respected oil pump manufacturer.

Some information passed along from a friend and long-time Chrysler tech, and he got it from an old AMC/Chrysler engineer:

"...the pump gears are not straight cut. They have a slight bevel (look closely). We did that for long term gear reliability. Trouble is, after the gears broke in, the pump would cavitate under high rpm/load operation (it didn't help that the sump tube design allowed for trapped air pockets)."

"If I remember, we built a number of 4.0L engines for the military. The MIL spec called for a straight cut gear and some other casting changes. The pump was improved and didn't cavitate. The high volume oil pump you got is the "MIL-Spec" pump."

I recommend the high-volume pump in the 4.0 engine.

BTW--"Those that can, do. Those that can't, teach."

I'll admit that I bought the HV just cause it cost less AND came with the pickup. My stroker is at least 30K, and I take it to red-line often, so other than the PITA to clearance it(which was less than the PITA to clearance the 4.2 crank), it does the job. I also run the bigger m301 filter and an extra 1/2qt of Brad Penn 10w30 racing oil(1300or1400ppmZDDP), so maybe the bottom end doesn't starve as much
edit: I will say that I do have high oil psi: the gauge is pegged cold and can get up to as high as 70 when pushing it warm, but normally is 35-40psi idle. I have been tempted to try a lighter weight oil or switch back to mobil1 hi-mi 10w30, which was my favorite oil pre-stroker, but want to ride Brad Penn out as a constant. Some would say that based on my higher than stock-pump oil psi, the HV pump is creating more parasitic drag and is also bypassing more unfiltered oil.

The pickup is not lower on the HV pump. Its the bod that sits lower. Pickup mounts in the same place as stock

Talyn said:

The pickup is not lower on the HV pump. Its the bod that sits lower. Pickup mounts in the same place as stock

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Correct. Oil pan needs a bit of massaging to clear the pump body. Easy.