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Discussion Starter · #1 ·
I have a Melling standard volume oil pump in my Dart SHP 383.
It comes with a high pressure spring installed.

Idle pressure is 25-30psi
Max pressure is 80psi

It comes with a stock pressure spring that you can install.
Dart recommends standard volume, and it seems like standard pressure as well.

Are there any drawbacks generally to the higher pressure?
I can check with Dart tomorrow regarding their specific oiling system.
I was just wondering what the pros and cons are in general...

Thanks!
 

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More for Less Racer
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2 cons....One is increased loading of the distributor gear, which can be a wear problem that can ruin the distributor gear, or both the cam gear and the distributor gear and rendering the cam junk.
Two is increased spark scatter from the pulsation of the pump drive gears being intensified.
Third would be it takes more HP to drive the pump....even if it is just a small Hp increase.

55-60 psi is really the max you should need in a SBC even with standard oiling uness turning over 7000 rpm regularly. With priority main oiling it should be more than enough.
 

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Discussion Starter · #3 ·
Excellent... I had already taken the high pressure spring out, but figured I'd get some feedback before installing the stock spring. I wonder why they have the high pressure spring installed... seems to make more sense to have the stock spring installed from the factory, and supply you with a high pressure spring, in case you have a situation where you want the high pressure...?

Thanks Eric!
 

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I think it comes with the higher pressure spring installed due to the fact most less educated installers jump right to needing "max volume and pressure" because "that's what they heard to do from Uncle Bubba/cousin Elmer/??? Magazine says so".

That and lesser chance of "too low pressure" warrantee customer complaints would be my guess..
 

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Discussion Starter · #5 ·
The reason I thought it was odd, is because this is a Standard Volume pump... but I guess since it's in their "Performance" line, it makes sense to want to do it that way just to CYA.
Too much pressure isn't as bad as not enough...
 

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True Hotrodder
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I think it comes down to the use of the engine itself. I have never been a big fan of the higher oil pressures but if we are turning that puppy to 7k on a regular basis then maybe it's something to consider. On an average, hi-po small block I have never had any issues with a standard volume, stock pressure spring which I had shimmed about 1/16". This has normally given me a high pressure in the 55-60 PSI area and is more than plenty for a mostly street runner.
 

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I have a dart shp small block and below is the melling oil pump I am using and I also did research on the high volume pump and if I could use one or not etc and over on some other forums a guy named Carl owns a machine shop up in the North East somewhere but anyways he used the pump below on all of his builds and has had no problems and I have used it and used the spring that it comes with and I use 10w40 oil Valvoline dyno type and I get about 70 psi or a little more when cold out and then goes down to about 60 psi while cruising and did the same with 5w30 on first startup.

I use the shark tooth pump as it has a different type of gears that helps to not make it run so hard on the distributor gear at least that is what they say and I have been running it for two plus years without issue and it goes down to around 35 psi at idle give or take 5 psi if its hotter out. I read a lot of folks use it with there dart shp blocks and have great success with it.

I would not use a high volume pump but I don't know if there is a difference between it and the pump I am using which says it gives only 10 percent more volume over a stock pump vs the high volume ones which give 25 percent. I know the difference is the length of the gears in the pump.

 

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I have a dart shp small block and below is the melling oil pump I am using and I also did research on the high volume pump and if I could use one or not etc and over on some other forums a guy named Carl owns a machine shop up in the North East somewhere but anyways he used the pump below on all of his builds and has had no problems and I have used it and used the spring that it comes with and I use 10w40 oil Valvoline dyno type and I get about 70 psi or a little more when cold out and then goes down to about 60 psi while cruising and did the same with 5w30 on first startup.

I use the shark tooth pump as it has a different type of gears that helps to not make it run so hard on the distributor gear at least that is what they say and I have been running it for two plus years without issue and it goes down to around 35 psi at idle give or take 5 psi if its hotter out. I read a lot of folks use it with there dart shp blocks and have great success with it.

I would not use a high volume pump but I don't know if there is a difference between it and the pump I am using which says it gives only 10 percent more volume over a stock pump vs the high volume ones which give 25 percent. I know the difference is the length of the gears in the pump and the spring that controls what pressure relief it gives.

This pump might be no different then the high volume one except the pressure spring installed but I can't say for sure. I just made sure and asked around before I used it and so far no wear issues on my end of things.

 

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The high pressure is simply that point where the relief valve opens. The engine’s working pressure is established by the volume the pump puts in versus the volume that ‘leaks’ from all the clearances. The pressure bypass only works when the leakage is somewhere less than the input volume.

As stated running higher pressure takes more power off the drive which increases wear on the cam driving and distributor driven gears. For cams usually rollers that require Melonized or bronze driven gears this will increase the needed replacement of one or both gears, this is usually the distributors driven gear, but not always.

Before the Melling Shark Tooth and gerotor pumps for the SBC, my go to was the big block pump, which requires a special length intermediate shaft that is available. The advantages are greater volume and with 12 tooth gears much smoother operation compared to the 7 tooth SBC pump. I also like to ‘up the pump’ when using remote filters and or coolers as the added restrictions of distance, fittings, direction changes, and the filters or coolers themselves reduce flow volumes thus pressure as the input volume is reduced while the clearance leakage remains the same.

As far as clearance leakage is concerned wide bearing clearances leak more than tighter bearing clearances. The tendency in the good old days with high performance engines was to use wide side clearances with thicker oils under greater pressure, thus volume to maintain lubrication and cooling within the bearings. Modern thought taking advantage of modern thin synthetic oils is to tighten the clearances with these lower viscosity oils which allows running at lower volumes and pressures while still moving sufficient oil to maintain lubrication and cooling through the bearings.

My biggest complaint with these gear type pumps is their large pressure and volume excursions between idle and higher RPMs. This tends to push me especially with wet sump competition engines to high volume pumps to get the idle and dropped throttle oil flow up. The flip side with a gear pump is then having to bypass so damn much oil at speed. This adds heat to the oil but serves no lubricating needs and adds the problems of getting the bypass volume back into the pan without more disturbing the stored volume nor adding too much to the windage, so there’s another bag of tricks for this adventure that has to be employed.

The paragraphs above are most of the engineering drivers behind pump selection that need to be considered.

Bogie
 

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JS-70
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I have a dart shp small block and below is the melling oil pump I am using and I also did research on the high volume pump and if I could use one or not etc and over on some other forums a guy named Carl owns a machine shop up in the North East somewhere but anyways he used the pump below on all of his builds and has had no problems and I have used it and used the spring that it comes with and I use 10w40 oil Valvoline dyno type and I get about 70 psi or a little more when cold out and then goes down to about 60 psi while cruising and did the same with 5w30 on first startup.

I use the shark tooth pump as it has a different type of gears that helps to not make it run so hard on the distributor gear at least that is what they say and I have been running it for two plus years without issue and it goes down to around 35 psi at idle give or take 5 psi if its hotter out. I read a lot of folks use it with there dart shp blocks and have great success with it.

I would not use a high volume pump but I don't know if there is a difference between it and the pump I am using which says it gives only 10 percent more volume over a stock pump vs the high volume ones which give 25 percent. I know the difference is the length of the gears in the pump.

Good choice Erik, that pump works well with Darts advanced oil system.
 

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Hi volume pumps will empty a 5 qt pan before you get to the end of a 1/4 mile in a 12 second ride. Pulsations will cause some scatter in the ignition primary BUT, if the oil is to temp and not super high viscosity, it should not cause issue. Bearing clearances open some with use. Seems that a stock spring isn't quite enough and the next step is too much. Oil is for cooling the bearings as well as lubricating. This is where the volume argument enters. Some say a volume @ 40 is better than stock volume @ 60. If you have access and REALLY want piece of mind, put the higher pressure spring in it and watch an oscilloscope on a chassis dyno. If the ignition isn't scattering then smile and forget it. If it bounces, pull the distributor and either try a loaner or find a distributor machine.
 

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Hi volume pumps will empty a 5 qt pan before you get to the end of a 1/4 mile in a 12 second ride. Pulsations will cause some scatter in the ignition primary BUT, if the oil is to temp and not super high viscosity, it should not cause issue. Bearing clearances open some with use. Seems that a stock spring isn't quite enough and the next step is too much. Oil is for cooling the bearings as well as lubricating. This is where the volume argument enters. Some say a volume @ 40 is better than stock volume @ 60. If you have access and REALLY want piece of mind, put the higher pressure spring in it and watch an oscilloscope on a chassis dyno. If the ignition isn't scattering then smile and forget it. If it bounces, pull the distributor and either try a loaner or find a distributor machine.
IIRC There are either 4 or 5 different pressure relief springs available , its not either / or ...
 
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