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Discussion Starter #1
Hi
Turns out I have a Melling high volume oil pump. What is the thinking on these ?. I have read that the high pressure pumps cause distributor shaft problems. Is this true with the high volume ones ?.
Should I revert back to a stock pump ?. Any other drawbacks with these ?.
Thanks
 

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I was taught that high oil pressure is not good, kinda like high blood pressure. The better route is to get a regular pump and have it blueprinted (sharp edges of the gears smoothed down so it maintains its stock pressure).

Frank
 

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Discussion Starter #3
The pump is high volume not high pressure. I do not know if this affects the wear on the disributor shaft or if the problem only occurs with the high pressure pumps which would be harder to turn.
Thanks
 

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Discussion Starter #5
Do you mean the driveshaft BETWEEN the distributor and pump when you say 'hardened shaft' ?
I am concerned about the actual shaft in the distributor. I have read that if you use a high pressure pump this opens out the end of the distributor shaft and makes a sloppy fit for the pump driveshaft, and in severe cases ruins the end of the distributor shaft.
I wonder if this would also occur with a high volume pump.
 

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A high volume pump means you are moving more oil with the same oil pump speed. If you do not have a larger than stock oil pan it makes no sense to have a high volume pump. You can actually pump the pan dry in some instances.

A high pressure pump has a stiffer spring on the pressure relief valve. Thus, the oil pump will generate more oil pressure before the relieve valve opens to maintain a certain pressure. this type of pump can put excessive pressure on main and rod bearings. Newer engines are built to much tighter tolerances and typically hold better oil pressure than older engines. Another problem with high pressure is that it will eat horsepower. Just think about it. Your putting more pressure on your rotating assembly as your rpms are increasing.


Ric
 

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Sounds like you guys are confusing "high volume" and high pressure" on oil pumps. Watch this video from Melling for a good explination.

 

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I'm not a fluid dynamics expert but, if I'm correct, "pressure" is a consequence of sending "x" volume of fluid (oil) though a restriction (oil passages). The pressure relief valve is in place to insure that the pressure doesn't get too high as the pump endeavours to push oil through the passages. The short of it, as I understand, is that a "high volume" pump will not deliver any more oil though your engine because to do so would necessarily raise the "pressure" as the oil presses through the restrictive oil passages... and this increasing oil pressure will overcome by-pass spring and the volume of oil going into the engine becomes regulated. HOWEVER, even on a relatively stock engine I believe a high-volume pump would provide good (if unnecessary) insurance against starvation. In a race application where the engine has looser tolerances (for reduced friction) a high "volume" pump can be necessary to insure that "pressure" is maintained.

On the other hand I may have no idea what I'm talking about. ;)
 

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Woody at Fordstrokers.com told it to me like this: If your building a stock motor, use a stock pump. HV pumps are for race engines built with loose clearances to wind up RPM's on the strip faster. Larger clearances need a higher volume of oil filling the voids. Did Ford build your engine with a HV pump? It provides 0 horse power.
 

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Nothing is free - High Volume consumes a little HP and is really unnecessary unless you have an engine that was built with tolerances requiring higher volume as has been stated. Never heard or seen a post regarding recurring oil pump issues with stock pumps. I would put it on EBAY and go stock but that's just me...

M
 

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Discussion Starter #12
OK according to the Melling video the high volume pump is ALSO a high pressure pump.
My original question asked whether or not the high volume pump would damage my distributor shaft. Now I see it is also a high pressure pump I think I know the answer.
I will go back to a stock pump and use the Melling to stop my trash can from blowing away in the wind.
Thanks all.
 

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I've been using a melling high volume pump for the last 43,000 mile in my Hi-Po engine.

does it use a bit more HP ? yes it does. does that matter? no it doesn't.

I even use a heavy weight oil, Mobil 1 15w50 most of the year. Again, no problems, unless you consider having decent oil pressure at all times a problem

All the talk about the pump drive shaft twisting or breaking is total BS. It is common practice to use a chrome moly pump drive shaft when using the high volume pump, and if you do that you will have zero problems.

Z.
 

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"..............I think I know the answer. I will go back to a stock pump and use the Melling to stop my trash can from blowing away in the wind.
Thanks all.
I will send you a brick for your trash can lid, and you send me your worthless high volume pump (if you don't mind me getting the better end of the deal)

Z.
 

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OK according to the Melling video the high volume pump is ALSO a high pressure pump.

A high volume oil pump can be normal pressure or high pressure. A normal volume pump can be normal pressure or high pressure. It all depends on which spring you have in the pump. There are two different parts to an oil pump in these engines. The actual pump part and the pressure relief. Unless I was building a stock motor, I'd put a hardened oil pump drive in. They are very cheap.
 

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Discussion Starter #16
I've been using a melling high volume pump for the last 43,000 mile in my Hi-Po engine.

does it use a bit more HP ? yes it does. does that matter? no it doesn't.

I even use a heavy weight oil, Mobil 1 15w50 most of the year. Again, no problems, unless you consider having decent oil pressure at all times a problem

All the talk about the pump drive shaft twisting or breaking is total BS. It is common practice to use a chrome moly pump drive shaft when using the high volume pump, and if you do that you will have zero problems.

Z.
Again
The interconnecting driveshaft between the distributor and oil pump is NOT my concern, I have an uprated Ford Motorsport item.
My concern is the end of the distributor shaft. I paid many dollars for a restored, correctly date coded distributor and on removing it recently I found it would not come out as the interconnecting driveshaft had started to turn in the bottom of the distributor and was stuck in there.
So from what I have heard the uprated pumps require more torque to turn and can ruin the end of the distributor - I do not want this to happen, this is the only reason I am considering returning to stock, to preserve the distributor.
Thanks
PS the deal on the brick is fine - bring it over when you come.
 

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OK according to the Melling video the high volume pump is ALSO a high pressure pump.
My original question asked whether or not the high volume pump would damage my distributor shaft. Now I see it is also a high pressure pump I think I know the answer.
I will go back to a stock pump and use the Melling to stop my trash can from blowing away in the wind.
Thanks all.
Look at it this way. The clearances in your engine are set at a certain size that does not change. If you increase oil flow through the same size opening you are going to have higher pressures. So a high volume pump will increase oil pressure.

A problem that can accure with high volume pumps is snapping the drive shaft from the oil pump to the distributor. This is obviously not a good thing since the oil pump stops pumping once the shaft snaps. If you do not realize what happened it could lead to a catastrophic failure of the engine. If you are running a high volume pump it is highly recommmended that you use a hardened drive shaft. I prefer the shaft made by ARP. Most likely the drive shaft is going to snap before you damage your distributor. I have heard of distributor shafts snapping however. I've never seen a drive shaft strip out the bottom of a distributor shaft but I suppose it is possible. If this were to happen you would probably have to have something lock up within the pump; I cant imagine that it would happen from the strain of spinning a high volume oil pump.

Personally, if you have a stock engine I would swap out the high volume pump for a standard pump as you have no reason to be running a high volume pump. As others have eluded to, a high volume pump is for engines with wide bearing clearances and rev in the 7000+ rpm range.
 

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"............ I have heard of distributor shafts snapping however. I've never seen a drive shaft strip out the bottom of a distributor shaft but I suppose it is possible. ..............."

I have the same observation. I have heard of, but never actually seen, stock shafts twisting or snapping. but never a hardened chrome-moly shaft failure. Likewise I've never seen a distributor that was damaged in that way.

Just do what makes you feel comfortable, and move on to the next issue.

"................... PS the deal on the brick is fine - bring it over when you come.
I am going to go over to my neighbors house right now and pry one out of wall.


Z.
 

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Discussion Starter #19
zray;4067294 I am going to go over to my neighbors house right now and pry one out of wall. Z.[/QUOTE said:
I dont want any old brick. You are getting the Rolls Royce of oil pumps. I want one of YOUR bricks, and not from behind the mail box either.
Hope to see you soon
Mark
 

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Personally I feel betterlooking at my oil pressure gauge as being a little higher and knowing there is never a case where that film of oil between my bearings is diminishing, to a crtical point, when the tach needle swings past 6500. One point not touched on - yet - is the fact that if you decide to run a high volume pump and associated drive remember that under certain circumstances you may pump your pan dry if you are not running a bigger pan. Oil starvation in this situation may spoil your day. Yes I run a hi vol pump in my cleveland and yes I use a large capacity pan.
 
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