Melling Oil Pump Spring Pressure

[Tom B.]

Re: Melling Oil Pump Spring Pressure

The length of the spring is only part of the equation. The total length of the wire and the diameter of the wire are also important. Also I would be amazed if GM and Melling used the same color coding on pump springs. I think your GM spring is orange because it was made orange. I have a few old GM springs in a can that I removed to put in white springs in the past and they all appear to be orange. We used to do a lot of this in the 60s and 70s. Of course we also would just stretch the stock spring a little to get the same result on occasion.

For example the GM 3814903 spring listed at 2 7/32 length has 21 coils, color code not listed in the parts book. The High pressure spring GM 3848911 has no length listed but is shown as having a white stripe. It is also 21 coils. Obviously it must have a thicker wire diameter and maybe even a longer overall length.

Tom

[Timothy B.]

Re: Melling Oil Pump Spring Pressure

Tom,

I agree with you except all the standard pressure GM springs I have seen are natural steel color but I have only handled a few.

[Tom B.]

Re: Melling Oil Pump Spring Pressure

I do believe you are right. The one I grabbed appears to have an orange cast to it but the others in the bottom are natural.

Tom

[Joe L.]

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 ?

Wayne------


The correct stock-equivalent pump for a 396 would be a Melling M-77. The Melling M-77HV can be used, but it's unnecessary. For a big block, using a high volume pump will usually cause no problems, though.

[Domenic T.]

Re: Melling Oil Pump Spring Pressure

This is probably why we inspected and used the old pumps years ago.

Never had a problem with an engine that wasn't built for the track, (excluding the 1/4 mile.)

We put a .030 washer behind the stock spring and life was good with a few more lbs of pressure.

I will say that I did find a few pumps that were not perfect and replaced them with one from another engine that was good. Maybe 1 out of 12 had a problem.

seems that the pump was the last thing to run out of oil.

DOM

[Duke W.]

Re: Melling Oil Pump Spring Pressure

Why do people buy Melling oil pumps? ...and on the internet???

Most used OE pumps are like new unless they have ingested debris. AND THEY WILL ACTUALLY DELIVER OE SPEC OIL PRESSURE!!!

If the pump is not reuseable, buy a Sealed Power OE replacement. None of the springs previously listed for Melling oil pumps deliver OE pressure for most SBs, which is 40-45 psi.

They are simple to disassemble and inspect. AND, you with a little time you can do some "blueprinting" as explained in "How to Hot Rod SB Chevies".

It's just insane, if not downright stupid!

Duke

[Jack H.]

Re: Melling Oil Pump Spring Pressure

Why do people buy Melling oil pumps? ...and on the internet???

Most used OE pumps are like new unless they have ingested debris. AND THEY WILL ACTUALLY DELIVER OE SPEC OIL PRESSURE!!!

If the pump is not reuseable, buy a Sealed Power OE replacement. None of the springs previously listed for Melling oil pumps deliver OE pressure for most SBs, which is 40-45 psi.

They are simple to disassemble and inspect. AND, you with a little time you can do some "blueprinting" as explained in "How to Hot Rod SB Chevies".

It's just insane, if not downright stupid!

Duke

Duke,

Normally I agree with your opinions, but I have to disagree with this one.

The answer to your question is easy. Several years back, many oil pump manufacturers INCLUDING Sealed Power changed the design of the SB Chevy oil pump presumably for cost reasons. Take a look at the attached picture which I just took from my stock.

The picture shows a Melling M55A (Z-28 high-pressure although it comes with a couple springs) which shares the same casting as the 10553 model that Tracy purchased. The melling pump is on the lower left.

The OEM Sealed Power unit that you are touting is in the upper right.

Take a close look at the casting boss in the vicinity of the mounting hole and just to the right. The "new, improved" Sealed Power casting is very thin in the transition area from the mounting boss to the gear housing.

Being a fellow engineer, certainly you can appreciate the issue when you have a heavily weighted gear unit transitioning thru a very thin casting wall down to the mounting boss. The cantilevered weight combined with the reduced wall transition area result in quite a stress concentrator.

The catastrophic failures of the "new and improved" cost-savings castings are well documented. I would hope that manufacturer's would revert back to the better casting, and maybe they have. The Melling and Sealed Power units in the picture were purchased a year or two ago.

For the record, even the standard M-55 that Melling sells now has this wimpy casting now. However, the Melling M-55A, shown in the picture, and the Melling 10553 still utilize the beefier casting.

So my solution is to buy one of beefier castings...and if it's cheaper on the internet I'm buying it there, but that's another story...and then simply swap out the spring with a GM #3814903 spring which you can easily get for a few dollars....heck sometimes you can even get one free if you're nice (see post #12 above).

FWIW, I do agree with the blueprinting suggestion, although I'm more leary about re-using internal engine parts with many miles on them. Wear or lack thereof is certainly visible, but issues like reduced fatigue cycles and such are not as easily recognizable, and just not worth the risk in my opinion considering it's only a $30-$40 part.

Just my 2 cents.

[Tracy C.]

Re: Melling Oil Pump Spring Pressure

Why do people buy Melling oil pumps? ...and on the internet???

Most used OE pumps are like new unless they have ingested debris. AND THEY WILL ACTUALLY DELIVER OE SPEC OIL PRESSURE!!!

If the pump is not reuseable, buy a Sealed Power OE replacement. None of the springs previously listed for Melling oil pumps deliver OE pressure for most SBs, which is 40-45 psi.

They are simple to disassemble and inspect. AND, you with a little time you can do some "blueprinting" as explained in "How to Hot Rod SB Chevies".

It's just insane, if not downright stupid!

Duke

Do you feel better now?

I'd rather think it stupid to gamble $80 that what my last Bubba builder installed was good to go. The pump shaft was loose and the weak casting horror stories in the archives moved me into the 10553. I have no idea of the origin of the old pump and frankly I don't have the luxury of time to buy books, study up and dive into a blueprinting project on a pump I know nothing about. I try to pick my battles and this one didn't capture my interests.

This really isn't a big deal Duke, I'll spend another $6 for a pack of yellow springs and have a few to donate to others in my position in the future.

tc

[Clem Z.]

Re: Melling Oil Pump Spring Pressure

Duke,

Normally I agree with your opinions, but I have to disagree with this one.

The answer to your question is easy. Several years back, many oil pump manufacturers INCLUDING Sealed Power changed the design of the SB Chevy oil pump presumably for cost reasons. Take a look at the attached picture which I just took from my stock.

The picture shows a Melling M55A (Z-28 high-pressure although it comes with a couple springs) which shares the same casting as the 10553 model that Tracy purchased. The melling pump is on the lower left.

The OEM Sealed Power unit that you are touting is in the upper right.

Take a close look at the casting boss in the vicinity of the mounting hole and just to the right. The "new, improved" Sealed Power casting is very thin in the transition area from the mounting boss to the gear housing.

Being a fellow engineer, certainly you can appreciate the issue when you have a heavily weighted gear unit transitioning thru a very thin casting wall down to the mounting boss. The cantilevered weight combined with the reduced wall transition area result in quite a stress concentrator.

The catastrophic failures of the "new and improved" cost-savings castings are well documented. I would hope that manufacturer's would revert back to the better casting, and maybe they have. The Melling and Sealed Power units in the picture were purchased a year or two ago.

For the record, even the standard M-55 that Melling sells now has this wimpy casting now. However, the Melling M-55A, shown in the picture, and the Melling 10553 still utilize the beefier casting.

So my solution is to buy one of beefier castings...and if it's cheaper on the internet I'm buying it there, but that's another story...and then simply swap out the spring with a GM #3814903 spring which you can easily get for a few dollars....heck sometimes you can even get one free if you're nice (see post #12 above).

FWIW, I do agree with the blueprinting suggestion, although I'm more leary about re-using internal engine parts with many miles on them. Wear or lack thereof is certainly visible, but issues like reduced fatigue cycles and such are not as easily recognizable, and just not worth the risk in my opinion considering it's only a $30-$40 part.

Just my 2 cents.

this should not be a problem just driving the corvette in and out of the trailer.

[Ronald L.]

Re: Melling Oil Pump Spring Pressure

Tracy,
Ole George is getting tight in his old age I spoke to him last year about the BB oil pickups, the one out of the car with debris was twice the opening of the current melling pick up. Of course they'll try an convince you it doesn't make a difference - but it had to or they would not have made them with the larger openings. Wayne I'd be curious what your pick up looks like, if older perhaps the larger opening?

[Duke W.]

Re: Melling Oil Pump Spring Pressure

That later wimpy casting is certainly a reason to consider reusing the OE pump - if it's still installed. I've never heard of a vintage oil pump failing unless it suffered catastophic debris ingestion or was whacked by shrapnel from a catastrophic failure.

Regarding the unfiltered oil issue - yes the pump is, obviously, before the oil filter, however, engine wear studies have shown that after initial run-in wear, a properly engineered and assembled engine produces very few particles until end of life, so if an engine is overhauled before significant end of life wear occurs, the pump - and the bearings, in fact, can often be reused.

When I overhauled my '63 340 HP engine at 115K miles, the Morraine 400 bearings looked effectively new, and the oil pump showed no wear, so I just dressed the housing and one gear with 400 paper to bring end clearance down to minimum, which I think was about .002". It probably didn't take more than an hour at my slow methodical pace, which made it one of the easier components to overhaul. (The badly cracked #7 con rod was another story.) I considered shimming the spring to increase the OE 40-45 psi hot pressure, but then figured that if the engine lasted this long including a few hundred miles of race track hot lapping, it didn't need more oil pressure.

I never replace parts apriori. My first consideration is to overhaul/restore them if possible even if it's a fair amount of work compared to buying new. Of course, I consider my time "free" for the most part since I'm primarily a hobbiest when it comes to cars.

Commercial shops will replace a lot of parts that are otherwise useable because in many cases it's cheaper to just replace them - and charge the customer - than the value of the labor to disassemble, inspect, and reassemble.

For the hobbiest/restorer you can save a lot by inspecting/overhauling/restoring as required instead of buying new. Think of the many cases were replacement or reproduction parts are inferior to OE. This applies to not only engine parts, but just about every other part on the car.

The whole oil pump issue has been very confusing over the past few years. The new wimpy casting is certainly something to avoid, and if that's all that Sealed Power offers, then I would recommend avoiding it. But does Sealed Power offer something equivalent to the M55A? It's my understanding that the M55A has a high pressure relief spring - on the order of 60 psi, which is too high for most OE small blocks.

If that's the case, one would have to buy the spring kit, but the lowest - 49 psi - is still on the high side compared to the 40-45 psi spec from most OE small blocks. Another alternative is to use the old spring, which should maintain oil pressure at the same level before the engine was overhauled. I've never heard of an oil pump relief spring "wearing out" or failing in any other way short of suffering consequential damage from a catastophic failure elsewhere in the engine.

Duke

[Wayne M.]

Re: Melling Oil Pump Spring Pressure

Tracy,
Ole George is getting tight in his old age I spoke to him last year about the BB oil pickups, the one out of the car with debris was twice the opening of the current melling pick up. Of course they'll try an convince you it doesn't make a difference - but it had to or they would not have made them with the larger openings. Wayne I'd be curious what your pick up looks like, if older perhaps the larger opening?

Ron -- I think my '961' with the Melling M77HV pump has the small opening. Here's the link to a thread exactly a year ago. Go down to post #6 for my pics. But again, I don't know the history of this engine, so might not be TFP on the pickup.

https://www.forums.ncrs.org/showthread.php?t=77339&highlight=oil+pickup&uid=7131

[Joe L.]

Re: Melling Oil Pump Spring Pressure

Ron -- I think my '961' with the Melling M77HV pump has the small opening. Here's the link to a thread exactly a year ago. Go down to post #6 for my pics. But again, I don't know the history of this engine, so might not be TFP on the pickup.

https://www.forums.ncrs.org/showthre...ickup&uid=7131

Wayne-----


I believe that virtually all, if not absolutely all, original GM oil pick-up screens for big blocks used the "small" oil inlet orifice.

As far as Corvettes go, you will see pictured below an NOS example of the GM #3860366 which was used for all 1965-66 Corvette big block applications. There is also a photo of an NOS example of the GM #6269895, the last available SERVICE piece applicable to 1967-74 Corvette big block applications (I have no idea why GM didn't also catalog it for 65-66 applications)

You will note that the oil inlet orifice size is the same for both. It's also the same for the other pick-up screens "between" the 3860366 and the 6269895 as well as all the passenger car pick-up screens I am aware of.

[Joe L.]

Re: Melling Oil Pump Spring Pressure

All-----


Attached is a photo of a Sealed Power oil screen pick-up #224-43620 (same as Melling #305S). This is the screen which has been sold in the aftermarket for SERVICE of most big block applications, including Corvette, for quite a few years. As far as I know and with one possible exception,, GM never used this style pick-up screen in PRODUCTION or ever offered it in SERVICE. However, it's possible they once offered a SERVICE pump with attached screen that was configured like this screen. I just have an "indelible" recollection of such a piece but, try as I may, I have not been able to find it. As I recall, it was a SERVICE pump for an L-88 application and it's possible the same pump was used in PRODUCTION.

Also, note that the Sealed Power pick-up screen pictured was actually manufactured by Melling (note tiny "M in an oval" manufacturer's ID mark on the back of the screen). I believe that Melling manufactures all of the screens sold under Sealed Power part numbers. I think it's also likely they manufacture some or all of the oil pumps sold under the Sealed Power brand.

By the way, this thread seems to have "diverged" quite a bit from its original subject.

[Clem Z.]

Re: Melling Oil Pump Spring Pressure

SBC use 5/8"dia pickup tube and BBC uses 3/4" dia pickup tube.