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Oil Pump For Stock 440

66Satellite47 said:
No didn't fail physics in high school or in engineering school, or in 35 years as an engineer that learned to be be a specialist in pump applications and design. Your statement does not consider all the factors in fluid flow.
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I TOTALLY AGREE WITH YOUR PREMISE....the volume and pressure relationship is fundamental. Wether a high volume pump or standard volume pump is required, needed or just wanted, is a matter of personal choice, intended application and the applications requirement.
One of the biggest determination of which pump is required or "best" is the engine's bearing clearances of both the main and rod bearings, followed by the valve lifter bores, and the cam bearings, and lube oil hot viscosity. The greater the bearing clearances, the greater the VOLUME of oil the pump must deliver to maintain a given pressure. The converse applies: the tighter or smaller the bearing clearances, the lower volume of oil will be required at a given pressure, or the pressure increases to the relief valve setting. IF, the bearing clearances are excessive, the higher the volume will be required but the pump cannot deliver the required pressure, the delivered pressure will be lower, assuming all other variables remain the same.
Personal information: my RS23V0A****** GTX, 440 six barrel engine has a high VOLUME Melling pump. My main bearings have 0.002"/0.0025" clearance and are full groove, Clevite tri metal type...steel backed copper tin overlay Babbitt. Rod bearings are the same at 002"/0.0025" thrust bearing per FSM. Full groove mains require more oil volume because the rod bearings receive oil for 360° of crankshaft rotation. Cam and lifter clearance per FSM. Oil is 10W-30 Mobil 1. Oil pressure cold is 80 psi at 2000 RPM; oil pressure hot is: idle 55/60 psi and 75 psi at 3000 RPM. I run the windage tray in the pan and one (1) additional quart. Is this combination "right" or correct? It works for me....is it correct for everyone....probably not....but.....to each his own preferences. Just my opinion of course...
BOB RENTON
 
RJ, I think you made an excellent point, the bearing clearances and lifter clearances are major factors in determining if a high volume pump is required. Fluid flow inside a Mopar motor is a little more complicated than most folks realize.
 
66Satellite47 said:
RJ, I think you made an excellent point, the bearing clearances and lifter clearances are major factors in determining if a high volume pump is required. Fluid flow inside a Mopar motor is a little more complicated than most folks realize.
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THANK YOU FOR YOUR COMMENT ....yes, the biggest determination will be the bearing clearances. This clearance is determined by the the relationship between the static dimension of the bearing shells and the rotating surface of the crankshaft held APART by the hydrodynamic wedge, formed by the lube oil supply, literally, separating the two surfaces, with the crankshaft "FLOATING" on the wedge of oil.

DEFINATION: hydrodynamic bearing is typically a low-clearance assembly that relies on a film of oil (and occasionally air) that develops space while the spindle is rotating. The bearings transmit (float) the load on self-renewing film of lubricant. The most basic hydrodynamic bearing is the journal bearing.
Lubricating oil from the engine oil system is supplied through the hole in the upper half of the bearing shell. A groove in the bearing shell retains some oil in the bearing when the engine is stopped. The groove also assists in spreading a film of oil across the bearing surface when the engine is running. When the crankshaft is stationary, the load is straight down and the oil is squeezed out from between the shaft and the bearing (Fig. 11.4A). As the crankshaft rotates, hydrodynamic lubrication acts and a wedge-shaped hydrodynamic oil film is established around the bearing (Fig. 11.4B). This film supports the bearing and, when oil of the correct viscosity is used, reduces the turning effort to a minimum. With the increase of the crankshaft speed the wedging action of the oil also increases, transferring the maximum pressure around the bearing to the left (Fig. 11.4C). Some oil leaks from the sides of the bearing, which flushes out contaminants and helps to cool the bearing. This requires continuous supply of fresh oil, which is provided by the oil pump to the bearing journal. The bearing wear mostly occurs during the initial start and continues until a hydrodynamic film is established.
Typical section view at the bearing interface:
upload_2021-11-25_9-24-16.png


Probably more information than you thought of, but it is what actually happens.....the crankshaft floats....
BOB RENTON
 
I'm surprised nobody posted Nick's Garage video on how to modify the Melling pump to fix the defect.
 
streetmachine said:
Hello. Just to revisit the topic I'm just wondering what would be a good replacement for the factory pump on pretty much stock '75 440 street engine with an automatic? The engine came out of an RV from what I can tell. I've seen conflicting information on high volume vs a high pressure pump. The car is pretty much a cruiser and doesn't see much hard driving. Maybe a full throttle run up to 75 mph on rare occasion and that's about it really. Just wondering what would be recommended in this case? Thank you in advance.
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Why do you want to replace the oil pump? The one that came with the motor is probably fine for your intended purposes unless you have witnessed a specific problem.

As with most aftermarket replacement parts, they are usually not as good as the factory original.

The Melling pumps that I have that are new from several years ago have terrible quality. The good news is that the pump is so overdesigned, their use in relatively stock application would be fine.

Unless you have a bearing problem, you do not need neither a high pressure nor high volume.
 
I don't have direct experience with the internals of the Melling pump, although that is what my builder selected for my 512 motor. I had many year's experience with the TRW high volume pump for my 440's and 400/451's. The TRW was a great product.
I also used a Milodon dual external pump for about 10 years. I did do lots of porting/grinding on the external remote oil filter housing though.
 
BSB67 said:
Why do you want to replace the oil pump? The one that came with the motor is probably fine for your intended purposes unless you have witnessed a specific problem.

As with most aftermarket replacement parts, they are usually not as good as the factory original.

The Melling pumps that I have that are new from several years ago have terrible quality. The good news is that the pump is so overdesigned, their use in relatively stock application would be fine.

Unless you have a bearing problem, you do not need neither a high pressure nor high volume.
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I believe that Melling is the OEM supplier of a lot of various engine components to a myriad of different manufacturers including Chrysler (at the time) plus GM for their DOD (Displacement On Demand) 6.2 L engines. These are the ones that are either V-8 or V-4 configuration (Cadillac Escalade, GMC Yukon Denali) by disabling 2 cylinders on opposing banks by altering oil flow to the respective valve lifters, turning off 4 cylinders. Similar to the old Cadillac V-8-6-4 designs but an entirely different concept. Look up: www.Melling.com to see what they offer....definately NOT a "one trick pony"......
BOB RENTON
 
RJRENTON said:
I believe that Melling is the OEM supplier of a lot of various engine components to a myriad of different manufacturers including Chrysler (at the time) plus GM for their DOD (Displacement On Demand) 6.2 L engines. These are the ones that are either V-8 or V-4 configuration (Cadillac Escalade, GMC Yukon Denali) by disabling 2 cylinders on opposing banks by altering oil flow to the respective valve lifters, turning off 4 cylinders. Similar to the old Cadillac V-8-6-4 designs but an entirely different concept. Look up: www.Melling.com to see what they offer....definately NOT a "one trick pony"......
BOB RENTON
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Right. But I don't think they were an OEM for the oil pumps being discussed. Melling calls their oil pumps "aftermarket" and they are physically different than the factory oil pumps that I have. But it's irrevelant, poor quality is poor quality. And in light of what I believe to be true regarding Melling quality, I would not replace a factory oil pump for a new aftermarket pump simply for the purpose of having a "new" pump unless I had data showing a problem. If data suggested worn rotors, I would try to source new rotors. But that's just me.
 
Thank you all again. The reason why I asked the question about the oil pump is because I wanted to have a spare on hand just in case I needed it. From what I remember last I've been noticing some different pressure readings from what little I haven taken the car out. I just got the car started after a 5 year nap a couple of days ago and my cold oil pressure is around 50 psi according to the factory gauge but, can't remember the warm oil pressure. I could of swore in the past my cold pressure was 60-70 psi. The other reason why is that this car has been cobbled together and I'm trying to fix/undo that bit by bit. I'll give an example(s) on the engine, there is still an EGR valve hooked up and the throttle pressure linkage (now replaced) was one from the RV application. Plus the mileage on this engine is unknown but, seems to run well enough. I've already replaced the sending unit and gauge already. I need to see what my warm pressure is once I resolve some other issues first.
 
Lots of discussion here. But the simple fact is that for a basically stock 440, a stock OEM oil pump is just fine. pull it apart, measure the rotor clearances and clean the pressure relief valve. You're good to go. Unless the motor has sustained significant damage, those pumps will last an extremely long time. Generally, there is sure no need for a high pressure or high volume pump.
 
BSB67 said:
Right. But I don't think they were an OEM for the oil pumps being discussed. Melling calls their oil pumps "aftermarket" and they are physically different than the factory oil pumps that I have. But it's irrevelant, poor quality is poor quality. And in light of what I believe to be true regarding Melling quality, I would not replace a factory oil pump for a new aftermarket pump simply for the purpose of having a "new" pump unless I had data showing a problem. If data suggested worn rotors, I would try to source new rotors. But that's just me.
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OK.....BUT....who made the OEM pump? Was it Chrysler Corp or who?? There are just too many specialized pieces and parts for one company to make everything.....like: door handles or wheel lug nuts or heater control knobs or seat cushion springs or spark plugs, or filters.....did Chrysler manufacture ALL the nuts and bolts, pieces and parts.....NO.....did Chrysler subcontract to a specialized manufacturer, like Melling, for engine components?? Probably....but without physical proof....one way or the other....is strictly supposition.
I agree with the QC issue noted, but, what was it exactly and was it: just the individual pump in question or was it the entire manufacturing run and how was it resolved....was it poor castings with porosity or internal dimensions out of tolerance or just poor performance (low volumes and pressures produced).
Again....is a high volume pump better (or worse) than a standard pump on an otherwise "stock" engine....who is the best person to make that determination......me (NO) or you (NO) but the owner of the engine and his/her requirements or desires or cost objectives..... Just my opinion of course.....
BOB RENTON
 
The last Melling HV pump I used (New), I pulled apart to clean before using it, and it was filthy inside, right at the oil inlet hole, like it was sitting around uncovered in a grinding area?
 
RJRENTON said:
Again....is a high volume pump better (or worse) than a standard pump on an otherwise "stock" engine....who is the best person to make that determination......me (NO) or you (NO) but the owner of the engine and his/her requirements or desires or cost objectives.....
Click to expand...

As stated earlier, my recommendation is to run the original pump, and based on data, decide what to do.

What is your recommendation for the OP?
 
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