Oil pump questions

[Jerry G.]

Re: Oil pump questions

I don't think a pump change is going to fix the symptoms you've described. I'd do a leak down before getting too much farther along. Jerry

[Joe C.]

Re: Oil pump questions

I don't think a pump change is going to fix the symptoms you've described. I'd do a leak down before getting too much farther along. Jerry

+1

Also, if you measure the end play between the gears and the pump cover at .0015" or less, then you don't need any priming aids. If the end play measures more than .0015", then make it so.

[Dennis O.]

Re: Oil pump questions

Don't any of you guys read the whole thread? One of the symptoms is a pegged oil pressure gauge (yes I've double-checked it). I have to believe that the rebuilder (he's dead; I can't find out what he did now) put in a Hi-Volume Hi-Capacity pump. I think going to a standard pump will cure that particular symptom. Also, I have done the usual tests when there are problems like this. Compression and leak-down are within limits.

[Jim L.]

Re: Oil pump questions

All oil pumps are positive displacement pumps..... turn the shaft and an amount of oil comes out which is determined mainly by the sizes of the gears. System pressure is determined by the relief spring once oil volume out of the pump exceeds the internal leakage.

To answer your original question, I'd use the GM spring John Hinckley suggested. I don't see any reason to change pumps.

Jim

[Ralph E.]

Re: Oil pump questions

Dennis, a few years ago I had the same problem. Oil pressure was too high. The gauge was pegged except at idle. I tried another gauge just to verify it was not a gauge problem. Once I confirmed gauge was OK I contacted Melling, told them my problem, they sent me a new pump and I installed it. Problem solved. I think the initial Melling pump that I installed had the wrong spring.
Good luck.

[Mike G.]

Re: Oil pump questions

As some of you know, I have been having problems with the freshly rebuilt L79 in my '67. A couple of symptoms are a puff of blue smoke at startup, excessive oil consumption, oil fouled plugs, and super-high oil pressure. (The only time the gauge is not "pegged" is at a full hot idle, when it still shows 50 lbs.) The car seems to run great except for this, so I have decided to remove the oil pump and replace it with a Mellings 10553 standard pump I just received. I plan on removing the bottom plate and pack the gears with grease (if not already done so), and tack welding the pickup to the pump. The pump came with an extra spring and the following note :

" This oil pump comes assembled with a high pressure relief spring. The enclosed yellow spring will drop the oil pressure 10 to 15 psi. Changing the spring will not affect the engine oil pressure at low speeds (idle)."

So my question is, which spring should I use? I am more into driving the car over showing it or racing it. (I would probaly have a much greater tendenacy to show it than race it.) One of the things I have found out in getting this car to run and drive as well as it currently does is that the original GM engineers had just about everything right when they designed these cars, and factory settings are usually the optimum.

Also, this is the last time I will ever have a basically stock enging rebuilt by a shop specializing in race engines, not matter how highly recommended they are. They do you "favors" you don't need.

Dennis:

the 10553 (which I use) comes assembled with a high-pressure spring. Here's the dope on Melling springs:

49# GREEN Melling #55049

58# YELLOW Melling #55058

70# PINK Melling #55070

I had to research this info when I finally decided to fix my high oil pressure problem (same as your situation but on a 300hp motor).
Went with the green spring and all is well up to redline.

Mike

[Dennis O.]

Re: Oil pump questions

Mike, Thanks for the informative, to the point response. I will be getting a green spring and proceeding as I planned. Denny

[Jim L.]

Re: Oil pump questions

Mike, Thanks for the informative, to the point response. I will be getting a green spring and proceeding as I planned. Denny

You asked for a "to the point" response and I gave you one. Why not use the specified GM spring if you are trying to achieve GM-specified oil pressure?

[Bob I.]

Re: Oil pump questions

Dennis:

the 10553 (which I use) comes assembled with a high-pressure spring. Here's the dope on Melling springs:

49# GREEN Melling #55049

58# YELLOW Melling #55058

70# PINK Melling #55070

I had to research this info when I finally decided to fix my high oil pressure problem (same as your situation but on a 300hp motor).
Went with the green spring and all is well up to redline.

Mike

Mike
What color spring did you remove, and replace with the green spring.

Bob

[Mike G.]

Re: Oil pump questions

Mike
What color spring did you remove, and replace with the green spring.

Bob

My Melling came with the 70# pink spring. Didn't work too well with my 60# oil pressure gage.

The green spring works great, and I would suspect that the GM standard pressure spring also works in the Melling pump body.

Mike

[Dennis O.]

Re: Oil pump questions

Jim,

I would prefer not to "mix 'n match" different manufacturers parts in my ouil pump.

Denny

[Gary R.]

Re: Oil pump questions

Hi Dennis
I rebuilt my 72 350 8 years ago and one of the things I had with it was oil pressue pegged and oil usage. Now I had a machine shop bore & hone the cylinders but I assembled it, part of which was to file fit the rings, deburr the oil pump, and assemble the engine using new World SR Torquer heads. I have to be honest I don't recall what spring was in the pump but it is difinately a M-55 Melling pump and pickup. I only run 15w40 Rotella oil in the car. While the higher gauge pressure is not correct I don't believe it caused me issue with the engine. The heads on the other hand did.

I was not convinced I installed the rings upside down or they didn't "seat" after break in or within a few hundred miles. It just didn't make sense to me those were the issues, I replaced the intake gasket and still had the oil issue. In my case I did some online research on those heads and the seals they used in them. They used umbrellas and now use positive seals. Since I rarely get a chance to work on my own vette the car sat for the past 8 years until I got the time on the past 4th of July to work on it. Prior to the work I contacted World to see if the guide OD was machined for positive seal size ranges. 3 calls and 3 different answers, basically no one could tell me so I was going to pull the valve spring on #8 intake to mic it up. Well as soon as I applied air pressure to the #8 cylinder it was blowing out the intake. The arm was off, so I tapped the valve with a hammer to see if I could seat it, couldn't so the job was delayed until I got the original 487x heads cleaned up and a basic valve jobs done. I also had them machined for .530" positive guides. Then I swapped the heads and the few miles I drove the car I didn't see the typical "oil fog" out the exhaust. The car felt stronger to me but I still have the same oil pressure.

So in my case it was 2 things, bad head seals and the M55 pump. Also once I removed the world heads and placed them on the bench, oil was running out the intake runners. The back of all the intake valves were covered with black burnt oil, the exhaust valves were lean white from the "out of the box" Holley I have on it.

If you swap the pump spring let me know how you make out, I may do the same. Keep me posted on what you find out with the oil usage issue. I did drive the car 5000 miles over that time and just kept the oil level up and swapped plugs about 800-1000 miles. Not the way to go but that is all I had time to do. Now it's been sitting a month waiting for me to check the timing and rejet it. Oh well the 4th of July isn't that far off!!

[Dick W.]

Re: Oil pump questions

Jim,

I would prefer not to "mix 'n match" different manufacturers parts in my ouil pump.

Denny

More than likely if you went to the Chevrolet dealer and bought a GM pump, it would be a reboxed Mellings pump. In their peak they virtually supplied all the US OEM's with I oil pumps

[Duke W.]

Re: Oil pump questions

I have no doubt that is true, but a GMPD sourced or an OE replacement pump in the Sealed Power or Clevite brands will have the GM OE spec pressure relief spring.

That doesn't mean than Mellings pumps sold under their own brand name has the OE spec pressure relief spring. In fact, from all the "high oil pressure" threads we've seen I suspect that all Mellings brand pumps have a higher than OE 40-45 psi spring (which is OE spec for all virtually all SB engines other than late '63-up mechanical lifter engines that had a 55-60 psi relief spring) unless you specifically ask for one to be supplied separately that you have to install yourself.

That's why I always recommend "OE replacement brand" parts like Sealed Power (Federal Mogul) or Clevite (Dana Corp.) for engine restorations, but few listen. Yes, in many cases you can buy the same part from GMPD, but it will almost always be more expensive, even if you get a trade discount.

It's the same old wive's tale that we've been hearing since at least the sixties: The OE parts are junk and the aftermarket hot rod stuff is way superior.

How many horror stories does it take before guys realize the aftermarket hot rod stuff is the problem?

Duke

[Timothy B.]

Re: Oil pump questions

Duke,

The Melling pump is a very nice part and the standard spring supplied with there M-55 pump is 58psi as I was told when calling a few years ago, that would be about right considering what I see on the gauge when driving my car. There is a provision in the cap for pin oiling and the casting seems nice and stout so changing to the GM spring may be all that's needed.

Dennis, why don't you call Melling and ask if the GM spring will work to reduce pressure in there pump and see what they say.