melling oil pump correct spring

[Bruce W.]

my oil pressure is to high. replaced the pump with a Melling standard pump. Pressure still to high 59 lbs at 2000 rpm. Here is my question:I have a green melling spring and also the correct GM spring. Which spring should I use? Can I use the GM spring Part #3814903 in a melling pump or should I use the green spring from Melling. Which will give me the most correct pressure for PV. idle pressure is about 32 lbs. I assume the pump I bought from CC had the wrong spring in it, is that possible? appreciate the help. Pan come off tomorrow for the third time. Thanks, Bruce

[Dennis O.]

Re: melling oil pump correct spring

When I bought my Melling standard pump from Summit to replace the Hi-Volume pump that the engine builder put in, it came with the Hi-Pressure spring installed and the medium pressure (Yellow) spring in a plastic envelope in the box the pump came in. I had to call Melling and they sent me the proper (green) spring which installed and everything worked out. The GM spring is probably correct, but for myself, I'd rather not mix different manufacturers parts.

[Bruce W.]

Re: melling oil pump correct spring

Dennis what are your reading when driving? I understand that it should be 45lbs.

[Timothy B.]

Re: melling oil pump correct spring

Dennis what are your reading when driving? I understand that it should be 45lbs.

Bruce,

It's really not clear if the GM 45 PSI spring will provide that spec (45 PSI) oil pressure relief in the Melling pump. The Melling cover may not position the spring in the same position so the spring may have more or less tension than if it were in the GM oil pump cover.

The engine idle pressure will not be lower, just the max relief pressure. If you have your original cover that may work on the Melling pump but I have not tried this.

I can report the same high pressure conditions on my 1967 327 300hp engine so I feel your pain because it's to much pressure for a stock engine.

[Dennis O.]

Re: melling oil pump correct spring

Dennis what are your reading when driving? I understand that it should be 45lbs.

Right around 50. I have to drive the car today (poor me!), so I'll take a closer look. Before I changed the spring, the gauge was constantly pegged. (My car is an L79 - 350 HP).

[Michael M.]

Re: melling oil pump correct spring

For what it’s worth, I’ll describe my experience on the subject. When I bought my ’67 300HP/327, it had a Melling M55 oil pump and the Melling #55058 (yellow) bypass spring. My oil pressure gauge read 30 psi at a hot 600 RPM idle, and 60+ at 2000 RPM.

I bought and installed a GM #3814903 spring and my hot idle (600 RPM) pressure is now 30 psi, and right at the GM spec of 45 psi at 2000 RPM - measured running Shell Rotella T 15W-40 oil. My oil pressure reading does increase slightly above 2000 RPM – a max of something close to 50 psi around 3000RPM.

I didn’t measure or count coils but the two springs look very similar and the GM spring fit fine in the Melling pump (pictures below). I wish I had thought of taking a picture of the two springs side by side. It’s been running about six months now with no issues. I did have to remove the pump to install the spring because the top half of the pump covered the tip of the retaining pin.

[Bruce W.]

Re: melling oil pump correct spring

Mike, I appreciate that information. Well, I put the GM 3814903 in the car. I will know tomorrow after the silicone sets. I took out the melling spring it looked yellow to me. I friend of mine gave me another melling spring he thought was green but looked to close in color to the one I took of the pump. I didn't know if you could put a GM spring in but I took my chances. Thanks you have confirmed that you can. PV is this week Hope I pass. Bruce

[Dennis O.]

Re: melling oil pump correct spring

Bruce, Sounds like everything worked out fine for you. I believe it would have worked right from the get-go, but I am uber-cautious about stuff like this. I don't know about back in the day, but I believe Melling makes OEM pumps for GM these days. If you didn't see my edited post above. My car runs right at 45 PSI fully warmed up ay 2300 RPM. Denny

[Joe L.]

Re: melling oil pump correct spring

Bruce, Sounds like everything worked out fine for you. I believe it would have worked right from the get-go, but I am uber-cautious about stuff like this. I don't know about back in the day, but I believe Melling makes OEM pumps for GM these days. If you didn't see my edited post above. My car runs right at 45 PSI fully warmed up ay 2300 RPM. Denny

Dennis------


Yes, in the old days the oil pumps were of internal GM manufacture. Somewhere along the way, that ceased and the pumps are now of Melling manufacture. Just when this began, I do not know. However, the current pump for Gen I and II small blocks is GM #93427692. This part number SERVICES both the standard pressure, standard volume and high pressure, standard volume applications. So, the box must contain multiple springs. Previously, the standard pressure and high pressure GM pumps had different part numbers although the only difference was the installed spring.

A curious "distinction" exists between the Melling M-55 and the GM #93427692, though. A Melling M-55 can be bought for about 35 bucks. The GM list price of the 93427692 is about 145 bucks. I just can't believe that the difference is entirely due to GM mark-up. I've got to believe that there is some other difference. At one time, Melling did offer a higher quality version of the small block Chevy pump under another part number. It carried a significantly higher price than the M-55. However, I don't think it's available anymore.

[Mike E.]

Re: melling oil pump correct spring

I ordered and received a new Melling from Summit last week. I plan on installing it in my solid lifter '65 L-76. Here are a few photos of it.

I'm a little bit confused after reading this thread and a few others on this topic on what spring to use for my application.







Mike

[Joe L.]

Re: melling oil pump correct spring

I ordered and received a new Melling from Summit last week. I plan on installing it in my solid lifter '65 L-76. Here are a few photos of it.

I'm a little bit confused after reading this thread and a few others on this topic on what spring to use for my application.







Mike

Mike------


This is the pump that I thought had been dropped by Melling. I was wrong; I just didn't dig deep enough. I'll also bet that this is the pump that GM sells under their part number 93427692.

This pump sells for about 3 times the cost of the M-55. So, how does it differ from the M-55? Well, for awhile, the M-55 used a "slimmed down" casting which proved to be vulnerable to breakage in service. However, I believe the M-55 now has the more traditional style casting, similar to this pump. So, what is the difference, then? My guess is the 10553 is an OEM quality pump and the M-55 is an aftermarket quality pump. So, what does that mean? I don't know in this case. But, let's face it, for an almost 3 times difference in cost there's just GOT TO BE some significant, if not apparent, differences.

As far as the springs go, I don't know what the "yellow" spring is all about. They say it's the "stock" spring. Since this series pump can SERVICE so many applications, it's possible that it is the "stock" spring for some of them (but not Corvette). Melling apparently does have this "green" spring that they send out on request. That's the one that seems to work and produce correct oil pressures for Corvettes. I don't know why they don't just also supply it with the pump. At one time, I think both were so-supplied.

[Mike E.]

Re: melling oil pump correct spring

Mike------


This is the pump that I thought had been dropped by Melling. I was wrong; I just didn't dig deep enough. I'll also bet that this is the pump that GM sells under their part number 93427692.

This pump sells for about 3 times the cost of the M-55. So, how does it differ from the M-55? Well, for awhile, the M-55 used a "slimmed down" casting which proved to be vulnerable to breakage in service. However, I believe the M-55 now has the more traditional style casting, similar to this pump. So, what is the difference, then? My guess is the 10553 is an OEM quality pump and the M-55 is an aftermarket quality pump. So, what does that mean? I don't know in this case. But, let's face it, for an almost 3 times difference in cost there's just GOT TO BE some significant, if not apparent, differences.

As far as the springs go, I don't know what the "yellow" spring is all about. They say it's the "stock" spring. Since this series pump can SERVICE so many applications, it's possible that it is the "stock" spring for some of them (but not Corvette). Melling apparently does have this "green" spring that they send out on request. That's the one that seems to work and produce correct oil pressures for Corvettes. I don't know why they don't just also supply it with the pump. At one time, I think both were so-supplied.

Sorry about the pictures being upside down in my previous post, fixed now! That was the first time I tried posting from my iPad, they looked fine on it then when I went to my PC they were wrong. Back to the pump.

Ok, now I understand why it cost more if it's OEM quality, I paid a tad over $90 for it, which is fine. I just re-read the first couple of posts. I think I had this thread confused with another one on the same topic. So what Dennis said is the green spring is correct and I should request it from Melling? I'll give them a call.

I think what also confused me is a solid lifter Corvette has a 80 lb. oil pressure gauges so I thought they used a different spring. Perhaps the higher pressure gauge was only to keep from pegging the gauge at higher RPM?

Mike

[Duke W.]

Re: melling oil pump correct spring

Late '63 through '65 mechanical lifter engines used the same pump body as other small blocks, but had a different spring to raise maximum hot oil pressure to 55-60 psi from the standard 40-45, and that's why these vehicles had 80 psi rather than 60 psi gages.

Owner's of vintage Corvettes are plagued by oil pressure issues because the aftermarket doesn't seem to know what spring to install.

The best way to ensure that oil pressure is in the correct range is to reuse the OE pump. It takes about five minutes to disassemble and inspect the pump. If there is no evidence that it has been damaged by ingesting debris it can be reused. Probably 90 plus percent of original oil pumps will pass inspection.

There is sometimes slight wear on the end plate and this can be dressed down with some 220-400 mineral spirits wetted paper on a flat surface. In addition one can set end play to the .002-.003" optimum value by dressing down one gear and the pump housing as required to achieve that value on both gears.

Unfortunately, most "engine builders" replace oil pumps, apriori, rather than performing the simple inspection procedure, often with a "high volume", high pressure pump, and many owners end up with excessive oil pressure, which just wastes fuel by pumping more oil than necessary, most of which is bypassed back into the pan.

So my question is: Why are you replacing the original oil pump, assuming it is actually the original Flint-installed pump?

Duke

[Chris D.]

Re: melling oil pump correct spring

Joe,
Believe it! Been selling parts to the OE's for several decades, GM included. Typical markup on service parts is 5 to 10 x production price, even when item is in high volume production. There is a high value placed on service I have always found hard to fathom based on just inventory and distribution costs. My bet is the GM and Melling pump are the same animal.

[Mike E.]

Re: melling oil pump correct spring

Late '63 through '65 mechanical lifter engines used the same pump body as other small blocks, but had a different spring to raise maximum hot oil pressure to 55-60 psi from the standard 40-45, and that's why these vehicles had 80 psi rather than 60 psi gages.

Owner's of vintage Corvettes are plagued by oil pressure issues because the aftermarket doesn't seem to know what spring to install.

The best way to ensure that oil pressure is in the correct range is to reuse the OE pump. It takes about five minutes to disassemble and inspect the pump. If there is no evidence that it has been damaged by ingesting debris it can be reused. Probably 90 plus percent of original oil pumps will pass inspection.

There is sometimes slight wear on the end plate and this can be dressed down with some 220-400 mineral spirits wetted paper on a flat surface. In addition one can set end play to the .002-.003" optimum value by dressing down one gear and the pump housing as required to achieve that value on both gears.

Unfortunately, most "engine builders" replace oil pumps, apriori, rather than performing the simple inspection procedure, often with a "high volume", high pressure pump, and many owners end up with excessive oil pressure, which just wastes fuel by pumping more oil than necessary, most of which is bypassed back into the pan.

So my question is: Why are you replacing the original oil pump, assuming it is actually the original Flint-installed pump?

Duke

Normally I would agree with you Duke, my problem is this pump has been hacked up already in a prior life. This "Improved" bracket and pickup shown below was installed and I have no idea what spring it was using.



Mike