Melling Oil Pump Spring Pressure

[Tracy C.]

Just purchased a model 10553 Melling oil pump from an eBay seller and I expected it to come with the extra "yellow" spring. Long story short, it wasn't there and the seller doesn't seem to be interested in providing one..even though every other seller on planet earth does. Silly me, I figured it was part of the kit from Melling.

The pump is a VERY nice piece but has the pink spring installed and according to this document, it is a 70 Ib spring. Everything I've read in the archives indicates that my late 63 L76 should have 55 - 60 lbs of pressure. The yellow spring is rated at 58 lbs and seems to be exactly what I need.

My engine is a fresh rebuild and bearing clearances are right at .002 for both the rods and the mains.

Does anyone have experience with the actual pressures obtained using the pink or yellow spring? Debating with myself to determine if I really want to order a new yellow spring and install it. Would I fail a PV with the pink one installed?

thanks,
tc

[Timothy B.]

Re: Melling Oil Pump Spring Pressure

Tracy,

Is the oil gauge in the car 80lb? The Melling pump is a nice piece but be careful with this relief spring.

I can't tell you about the pink/yellow spring, but I will say that with .002 mains/rods the car is going to have great oil pressure and will peg to the relief above 2000 rpm, idle pressure will probably be 30-35lbs.

Read a post last year from me about my experence with the Melling pump I installed on my 67. I am upset the stock Melling pump (old M-55) has a relief pressure 55-60 and closer to 60 Melling informed me. They sent me a green spring that's supposed to the be 49lb but I am not removing the pan.

[Clem Z.]

Re: Melling Oil Pump Spring Pressure

Just purchased a model 10553 Melling oil pump from an eBay seller and I expected it to come with the extra "yellow" spring. Long story short, it wasn't there and the seller doesn't seem to be interested in providing one..even though every other seller on planet earth does. Silly me, I figured it was part of the kit from Melling.

The pump is a VERY nice piece but has the pink spring installed and according to this document, it is a 70 Ib spring. Everything I've read in the archives indicates that my late 63 L76 should have 55 - 60 lbs of pressure. The yellow spring is rated at 58 lbs and seems to be exactly what I need.

My engine is a fresh rebuild and bearing clearances are right at .002 for both the rods and the mains.

Does anyone have experience with the actual pressures obtained using the pink or yellow spring? Debating with myself to determine if I really want to order a new yellow spring and install it. Would I fail a PV with the pink one installed?

thanks,
tc

contact melling and i bet they will send you a spring of your choice

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

contact melling and i bet they will send you a spring of your choice

I've already called and spoke to George. He didn't offer to send me anything, but told me I could order the 55058 package from Summit or Jegs.

I can order the parts through my local auto parts store and save some shipping costs, I just wanted to be sure it was worth my time. I was planning on buttoning up the bottom end this weekend. Looks like another delay unless I have any other options.

I even considered clipping a coil or two off the pink spring, but that would be a krapshoot at best.

tc

[Clem Z.]

Re: Melling Oil Pump Spring Pressure

I've already called and spoke to George. He didn't offer to send me anything, but told me I could order the 55058 package from Summit or Jegs.

I can order the parts through my local FLAPS and save some shipping costs, I just wanted to be sure it was worth my time. I was planning on buttoning up the bottom end this weekend. Looks like another delay unless I have any other options.

I even considered clipping a coil or two off the pink spring, but that would be a krapshoot at best.

tc

shorting a spring makes it stiffer. it works that way with suspension coil springs.

[Scott M.]

Re: Melling Oil Pump Spring Pressure

Tracy, I might have a new yellow spring I could drop in the mail for you. I'll double check later tonight for you.

[Timothy B.]

Re: Melling Oil Pump Spring Pressure

Tracy,

Do you have a original GM pump sitting around. If it's in nice condition it can be reused with the GM high pressure spring. I took one out of a old 327 I have and it is in nice condition, I would not hesitate one bit to use it over.

One other thing to try is to buy the GM high pressure spring but I am not sure how you would test, I don't know if the spacing in the Melling relief valve area is the same as GM.

[Scott M.]

Re: Melling Oil Pump Spring Pressure

I've used the GM Z28 spring in M55 pumps several times, no problem.

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

Tracy,

Do you have a original GM pump sitting around. If it's in nice condition it can be reused with the GM high pressure spring. I took one out of a old 327 I have and it is in nice condition, I would not hesitate one bit to use it over.

Tim, My old oil pump has no GM markings, just "USA", "12", "2" and what appears to be a very faint blockish looking "S" It does have an orangish color spring. Maybe this was once yellow and now oil stained ?.

I'll pull both springs out and compare lengths and report back.

tc

[Wayne M.]

Re: Melling Oil Pump Spring Pressure

First of all, I'm no engine specialist, but I've got a '65 396 2-bolt [961] with unknown history [bought it from a good friend so it can't be that bad]. I see it's got a Melling pump (at least the tag on one of the pump cover bolts reads 77-HV. Is this proper for a low-stress big block ?

I see that part in the Melling Catalog table of Tracy's post, and this thread got me to wondering what color spring I have. Looking at those packaged springs on the catalog cover, I see no color, so how do you tell what you've got ? And is the color visible as installed, or do you have to remove the retention pin to remove the spring ?

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

Wayne,

The color of the spring is visible from the end with the retaining pin.

Here is the new "pink" spring from my new pump and the old "orange" spring from my old pump. They are the same length but the wire dia on the new spring is .041 and the old spring is .043. The old spring also has more coils.

Anyone recognize the orange spring? The melling chart doesn't show orange. It seems to be slightly easier to compress between my thumb and forefinger.

tc

[Jack H.]

Re: Melling Oil Pump Spring Pressure

Tracy,

I remember the thread that Tim mentioned and had it bookmarked as I was needing a lower pressure relief spring myself. Here is the link to that thread:

https://www.forums.ncrs.org/showthread.php?t=68116&highlight=3814903&uid=4225

and another here:

https://www.forums.ncrs.org/showthread.php?t=54284&highlight=3814903&uid=5631

I have an extra GM spring #3814903 which is referenced in these two threads. I believe this is equivalent to the Melling "Green" spring and less pressure than you really want. I would be glad to send this extra spring to you if you drop me a PM with your address. Again, probably less pressure than you want, but thought I would offer just in case.

-Jack

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

Tracy,

I have an extra GM spring #3814903 which is referenced in these two threads. I believe this is equivalent to the Melling "Green" spring and less pressure than you really want. I would be glad to send this extra spring to you if you drop me a PM with your address. Again, probably less pressure than you want, but thought I would offer just in case.

-Jack

That is very generous Jack! Maybe someone here has the yellow spring and needs the green. We could do a three way trade.

tc

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

Tracy, I might have a new yellow spring I could drop in the mail for you. I'll double check later tonight for you.

Thank you...

[Timothy B.]

Re: Melling Oil Pump Spring Pressure

Is there any way to test the relief pressure with the pump off the car? The GM 3814903 spring is 2 7/32" and is a 45lb spring.

I have a Melling green spring and it's approx 2 3/8", I don't know the wire dia. but this spring is supposed to be a 49lb spring.

The plain steel spring in my old M-55 pump is 2 1/4" long and it makes 60lb+- oil pressure so I question the green spring above because to me it feels stiff compared to this plain spring.

There is a stop pin pressed into the other end of the relief passage which is why I questioned the spacing of GM/Melling pumps plus the location of the passage for return. IMO, the Melling M-55 pump is a nice pump I like the way the idler pin is oiled just disappointed with the high relief pressure.

Sounds anal to be worried but when you are driving and the gauge is pegged from excess oil pressure I personally don't like it. I would rather have the pump relieve to the supply port than my motor dealing with 60-70 lbs pressure which is not needed. Keep in mind a 327 with .002 clearances is going to produce oil pressure to the relief so be careful here.

My 63 has wider clearances (probably closer to .003) and carries 20-25 hot idle pressure but the engine has to be reved higher than 2000 to get to the 45lbs, this engine has a GM 3764547 pump.