Melling oil pump m55(a) dangerous design change

[461poncho]

I know it's old but it's good info so I copy paste the first tech post

finally found the cause of my oil pump problem.

called melling today and asked them a few questions about my oil pump cracking off.

guy named george at x134 told me that they had a design change this past year.

general motors asked them to make the casting thinner on the m55 series and who knows what other oil pumps.

melling initially didnt put warnings inside the boxes saying:

DO NOT USE THIS FOR PERFORMANCE APPLICATIONS.

what happens is with solid motor mounts and enough tire shake and the pump breaks off like it did on mine.

as an example of how much thinner the new m55 pumps are measureing the cross section where it broke

new pump .80 inch
old style pump 1.25 inch

I just happen to have an old m55a pump laying around.

hopefully this post can save somebody else some grief.

I seem to have gotten off fairly cheap
mag crank checked ok no cracks
polish crank
main and rod coated bearings.
and a new pump (this one from moroso) with a milodon support bracket!

melling told me the replacement for the new design m55a is 10553.

if you order an m55(x) your screwed.

why they didnt use the new number for the new design is ridiculous...

hope this saves someone else a catastrophe!

I pickup my bottom end stuff tonite and start assembling tomorrow...couple weeks outta do it.

ed

mark if you read this i think making it a sticky might be save somebody thousands of dollars!

------------------------------------------

is a hv 55 the same thing

---------------------------------------------------

I dont know about the pump body on that one. but i can tell you when viewing the top side ( looking down at shaft and mounting flange the weaker casting has 2 different levels on it)

another way to tell the weaker casting is when viewing the side of the pump with USA on it. above the USA marking you will see a rectangular shape in the casting that measures 1.125 x .375 roughly.

my opinon is many if not most suppliers arent aware of the change.

I ordered a blueprinted pump from moroso. no 22100. It arrived in the weaker casting.
when i picked up my crank at the machine shop we went thru the stock of melling m55 series pumps he had on hand. each and every one of them were the weaker casting. not a single box had the warning note inside that melling told me to expect.

on mellings website they list the new part numbers for performance pumps. they new numbers are for the old style better thicker casting.

note the better pumps all have at least a 5 digit part number.
listing from mellings website:
http://www.melling.com/select/oil_pumps.asp

ed

----------------------------------------

one other thing i want to add to this thread.

while at this show i pickd up mellings new M SELECT catalog.

what do know page 2 is devoted to "casting changes to the small block chevy oil pumps"

fwiw... No jacket from the ups truck yet. lol

ed

--------------------------------------------

Here's the reply that I got from Melling:

Cardinal,

Thank you for input ,we value our customers opinion.

Melling’s design of GM’s Small Block Chevy oil pump was updated in 2004, see attached bulletin. At that time changes were made to the standard volume, M-55 & M155, and the high volume, M-55HV & M155HV, pumps. The changes improved many aspects of the pumps as compared to the original GM pump. To respond to customers requests one of the areas that improved was the hot idle performance of the pump. Durability was improved by eliminating a possible failure mode as noted in the bulletin. Casting improvements allowed the wall thickness of the housing around the gears to be reduced to reduce weight. Additional support rips were added to the neck area on the high volume pump casting. For stock replacement applications the changes will only increase customer satisfaction with our products.

For performance applications Melling recommends an M-Select oil pump be used, especially in solid motor mount applications. Melling has available a full line of SB Chevy performance oil pumps. Not only does the M-Select line of SB Chevy performance pumps utilize the previous casting design but are available with design features to further increase performance and durability. In addition the M-Select pumps are CNC machined to exacting tolerances and surface finishes. The M-Select line was created to provide engine builders a cheap insurance policy to improve one of the most overlooked critical components in a performance engine build, the oil pump.

Melling is a world class designer and manufacturer of Original Equipment, Replacement, and Performance oil pumps. The changes implemented on the stock replacement GM SB oil pumps improved performance, durability, weight and cost. With the recent dramatic increases in raw material costs these changes have helped to reduce the cost increase that is passed onto our loyal customers.

I have attached the warning sheet (pdf) that is included in each Melling boxed oil pump. Some of our private labeled oil pump customers do not to have the warning sheet included in the packaging.

Thank You,

George Richmond

Tech.Mrg.

-----Original Message-----
From: Cardinal
Sent: Tuesday, October 17, 2006 12:37 AM
To: technical@melling.com
Subject: New FUBAR Melling HV M55 Pump


For your own sake, I think it would be in your best interest to recall the "new and improved" M55 small block Chevy high performance pumps, or change the part number, and/or put a disclaimer on them that they can fail if used in a high performance motor.

Trust me, you're going to ruin your business if you don't. I belong to three different boards (Gen II Camaro, Gen 1 S10, and a Gen III Camaro) and all three have posts from members warning others about the JUNK Melling oil pumps being put out on the market. More than one member has had problems. One went back to his engine builder who checked all of the pumps on inventory and found all of them had the new thinner casting. Another ordered a Moroso unit and it had the thin casting.

I sincerely hope that this is not a trend with your company. We've seen too many companies like TRW automotive and IBM (PC's) go down the tubes because of mismanagement and reduction in quality and/or performance of their parts. Melling oil pumps have been the benchmark for a top quality product and I sincerely hope that this event is an anomaly and not a trend.

Sincerely,

Cardinal

__________________________________________________ ____________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact the Melling IS&S Group
__________________________________________________ ____________________




M-55 and M155 GM OIL PUMP IMPROVEMENTS FOR 2004

In 2004 Melling Engine Parts will be releasing updated versions of the M-55 and M155 oil pumps. The new M-55 and M155 will have a new look due to a new housing and cover casting. The housing will now have a drilled outlet hole much in the same manner as the original GM pump. As compared to the original GM design the outlet hole has been re-positioned to improve the alignment with the bearing cap to improve oil flow up to the main oil gallery.

The cover design has also experienced a change. The relief valve bore is now machined as a blind hole with a step near the end for the relief valve to seat against. Leakage around the relief valve will be greatly reduced since the valve seats on the end of the valve bore. This will help to improve low rpm performance. This change eliminates the need for the press-fit plug and possible failure mode concerning the press-fit on the plug.

The changes to the relief valve are minor. The end configuration has been changed to match the chamfer on the valve bore. A 90-degree edge has been added to help clean foreign material off the valve bore wall.

The groove pin has been changed from a 3/32” diameter tapered pin to a 1/8” diameter straight pin. This change is to increase the strength of the drill to reduce tool breakage. Pin orientation will no longer be an assembly issue by removing the taper from the pin.

“Quality in all we do”


Melling Engine Parts has an oil pump for almost every application. Whether you need a stock
replacement pump, or one of our M-Select Performance pumps, we build quality into every one.
Special attention to performance and durability has been given to all of the new line of M-Select
Performance oil pumps. Take a look at what the leading manufacturer of oil pumps can do for your
performance lubrication needs. All pumps are tested for pressure and volume and hand turned before being bagged and boxed. The informational charts on the following pages will assist you making the correct choice for the MSelct
oil pump that best suits your needs. In Melling’s continuous drive to improve the quality and customer satisfaction of our products a series of design changes were recently made to the body casting used to manufacture the M-55 and the M155 family of oil pumps. Melling supplies these pumps to the Original Equipment market, as well as the aftermarket. The major design change was a weight reduction in the body casting. The lightening of the casting as and the drilling of the outlet hole resulted in a change in the appearance of the Melling pump. Melling will continue to use the old casting design for the pumps manufactured for our M-Select performance line of products. We highly recommend all performance engine builders choose one of our M-Selct oil pumps.

M-55HV 10550
“Very Important”

Casting Changes to the Small Block Chevy Oil Pumps Location of weight reduction done per General Motors request
__________________
Cardinal

-------------------------------------------------

[jays64II]

good shit poncho ! glad it got saved !

[ed hess]

jay

this needs to be made as a STICKY for a long time.

over on the sy/ty.net people are still running into issues like what i encountered.

as long as the m55 pump is out there the uninformed will keep buying it!

so make this a sticky or whover becomes the moderator of this section.

btw i want to nominate adam aka adamsvega once he signs up here.

hey adam thanks for volunteering. wtg!

ed

[jays64II]

I'm not a mod Ed but I agree with you. Mike...can ya help us out ?

[jeffmotorman]

Melling discontinued the lightweight oil pump casting of the M55, M55A, M155 oil pumps about 2 years ago. Any new, unused pump with the lightweight casting that was prone to failure can be returned to Melling for exchange as it is old existing stock, and not currently in production. The Melling Select oil pumps are an affordable upgrade and offers better gear stability than the OEM design oil pump. The Melling Select pumps also can use a bolt on screen. Their screens are very affordable for deep oil pans.

[ed hess]

jeff
where did you see , hear or read that?

last time i looked the m55a was still in their catalog listing.

ed

[jeffmotorman]

The parts have been manufactured since late 2005 using the original heavier castings. The part numbers M55, M55A and M155 are still listed and sold with the heavier castings to the retail market only. Melling was pressured to redesign the casting by GM as an OE vender. For the retail market, however, Melling was aware that the usage of these pumps extended further than OE usage and as failures occured, went back to the original castings for the retail market.
I have been a WD for the Melling line for almost 20 years and I have contact with the tech support at my disposal. I notified them of the situation as I too experienced the pump failure on 2 occasions. It took almost a year after the failures came to light for Melling to go back to the original casting style.

[cmracing]

You know what kills me... I had a pickup fall off my Melling pump, not their fault, the person that welded the pickup on screwed that up. What pisses me off is that I bought a brand new Melling pump from Canton since they are the ones that made the oil pan. Got it with the 3/4" pickup tube. They knew this pan is in a drag race car, it looks like a comp eliminator pan, full length pan that holds 9 quarts. What did they send me??? The JUNK PUMP!!! Unreal. How could they have NOT known about this issue? I told my engine builder to send it back to them and let them keep it and get me another NEW pump! Could care less about the $75 for the pump, they can keep the money. To risk a $10K motor with a garbage pump is unreal.

[jeffmotorman]

Melling also has a premium line of oil pumps for the performance market sold as Melling Select products. This line has heavier pump bodies and a stronger alloy, supported pump gears with a pilot in the cover, adjustable regulator spring and bolt on screens. They also have screens for 7.5" to 9" deep oil pans that are very reasonably priced, both press-in and bolt on styles. This is the stuff that should be used in high performance applications.
The line also includes cams, performance timing components, pushrods, stainless valves, racing springs, retainers and locks, hard alloy cylinder sleeves, rockers, valve guides and seats.
Overall, the quality of all of the Melling products sold is very good.

[Rogers Performance]

There are some problems with the melling select pumps also a few guys have split the gears since they are made from powded metal.

[Turbo chevelle]

Can someone post a pic of the 2 different parts (old and new)?

[crazedmullin]

We are going on and on with defective melling select oil pumps with the adjustable relief as we speak. Our pump is in a sbf motor though. We are on our 3rd pump with low psi right out of the box. Melling told us to bench test the pump, make a plate to bolt to outport and test pressure deadheading, should be close to 100 psi at 3000 rpm , we have not been over 55 psi yet...just thought i'd throw that in there, they definately have some QC issues....