Oil pump - high volume or std volume?
 

OK, so now I have resigned myself to pulling my engine to inspect / replace my oil pump. I have another thread out there about wearing out distributor drive gears, and when I checked my pump by turning it with a screwdriver, it felt stiff and somewhat notchy.

A friend has a pump that he gave me with just a few hours on it that he took out of his HP500. He took it out because he was seeing 25 lbs of OP at idle and about 45 lbs at speed. He was concerned about oil pressure because at the time he was running a supercharger and wanted to make sure he had a good oil film on the bearings.

After pulling this pump, he discovered that it had the low pressure spring installed, hence the low pressure readings. He installed a high pressure spring, and while spinning the pump with a drill with the engine on a stand, the pressure jumped up to more "normal" levels. Nevertheless, he decided to run the new HV Melling Select 10778 pump that he had purchased, just for the extra safety factor with the supercharger.

My question is this: I know that the general recommendation on this board is to run the Mellings 10778 pump (which is what I have now), but I have also seen it stated that running these high volume pumps, especially with the thicker oils, can result in distributor gear wear and undue power consumption. Will I be all right to run the standard volume pump with the high pressure bypass spring? I believe that is what the HP500's are running stock, and I think I was running a standard volume pump in my old 454 that was still going strong at 550 hours. Is it really necessary to peg the oil pressure gauge at 80-90 PSI cold pressure?

One more question - I am really hoping that I am not pulling this thing out of the boat only to discover that there is nothing wrong with the pump. How much resistance should I feel when I turn the pump by hand with oil in the pan? Is it normal to feel it "catch" slightly as the gears turn inside of it?

For what it's worth, I found this thread from 2010. In it, Raylar posts his reasons (valid ones) for his preference of the 10778 pump. However, towards the end of the thread, "jackhammmer" asks a question that is much along the lines of what i am dealing with:

"I have an oil pump (the good one as described above) that appears to drag slightly when rotating by hand (using a shaft made for spinning it). When I put it on the first time I swear it would rotate smooth. Removed pan, took pump back to bench for a close look. Everything looked fine and it felt smooth rotating it. I went and did some simple blueprinting to be certain it was ok. Put it back in and it was still smooth. Put oil in and the drag is back! wtf? I would say about 25% of the rotation has a slight drag when it's pumping oil. I hooked my drill to the tool and looked for surging oil pressure but it seems to be working perfectly. Anyone hear of such a thing? Engine #1 didn't do this."

Nobody answered him. Is this an issue with manufacturing variances, or do these pumps just naturally have more drag to them?

http://www.offshoreonly.com/forums/g...il-pump-4.html

Imo , high volume-high pressure would be a welcome factor in a hard working marine application as long as you have the oil pan to support it . Lots of oil gets pumped up top , valve train , right where you need it to keep things cool and lubed with the steady high r.p.m.'s we pull . From what i remember there should be no catchiness or snagging when you rotate the pump only a nice easy bump bump as the impeller gears mesh . Nice an smooth like the rest of your rotating assembly when spun . I hope this helps you .

Yes , when submerged in oil and pumping there will be drag and it gets harder to turn because it is pumping oil . On a stock non performance application a HV-HP pump would not be needed or desired .

fixx
 

i use the low pressure spring with a couple machine washers to bump the pressure a little,,,give you around 30-35 psi at idle and 55-60 @ 5k..

with light oil it will turn smoothly,heavier oil it will ratchet and bind,,this is from the oil going between the 2 gears and trying to compress it in a closed space..(normal)

Having trouble discerning catchiness and snagging from the "bump bump" of the gears that you describe. I hate the idea of pulling this thing, but I have this nagging thought that the worn distributor gear is trying to tell me something. Either that or the eBay seller who sent me the melonized gear sent me a standard one instead.

Wish I could find someone with a 10778 pump sitting in 20W-50 oil that I could compare. :)

So, from what you guys are telling me, I may not actually have an oil pump problem. I might just drain all the oil out tomorrow and see how it feels then. Should that smooth it out? If so, then I guess I'll drop in the distributor with the new gear and see how it runs.

fixx
 

are you seeing alot of oil pressure rite now ? is so that would put allot of pressure on a bronze gear which is designed to ware out instead of the cam..are you running a roller cam? have you checked the cam button and spring if its a mark engine?

MrFixx, it's a Gen VI, so it used the stock shouldered cam with the retainer. End play was supposedly checked by the builder when the cam was installed and degreed. It had the GM melonized gear, which is what they advise running with the stock GM Billet cams. Oil pressure was pretty high when cold - probably 75 - 85 PSI. I tried to be careful not to run it hard until the oil temp gauge started to get up around 180*.

I covered a lot of this in my other thread - here it is for reference:

http://www.offshoreonly.com/forums/g...illet-cam.html

fixx
 

i read some of that trend,,the dist gear you have is for a stock cam and its not the correcxt one for a k5billit cam. some cam mfr's will have the lobe portion as billit and the dist gear portion would be a pressed on cast portion...who was the cam mfr and do you still have the cam card?

you can change the shims under the rotor but you will have to take the gear off and pull the shaft out to see if their is any so the gears on the cam and dist will mesh properly..