skinny z

It came to light that the Melling M55 might not be all that it's cracked up to be. Changes in the casting, namely in the pursuit of weight savings, have resulted in a weaker component. So much so that one member on another forum raised the alarm and posted a warning document from Melling regarding its suitability in a high performance application. My pump came with no such warning however when comparing it to the non-Mellling pump (or at least unidentifiable as there's no casting info) there are obvious differences.Some good such as improved radii and relief clearances in the casting. Some not so good such as reduced material at the mounting boss.


Covers ( Melling on the right)


Melling body


Generic body


Melling mounting boss


Generic mounting boss

Pickup tube diameter and spring rating notwithstanding, I'm interested to know if this part should be shelved.
Anyone have any feedback on this?

skinny z

I can't say for sure. I'm inquiring on another forum (Speedtalk) but nothing date-wise.
What I can say is that an internet search has posts raising this concern back in 2006!
I don't know what to make of it.
FTR, whats your pump's present application?

sofakingdom

iTrader: (1)

Yeah, it was back in the 2000s. There was another part # that was more similar to the older version but I don't recall what it was. May or may not still be available. Might need to go with another vendor if this is a major concern. Although, I have yet to ever hear even anecdotal accounts of somebody's brother's girlfriend's boss' cousin's roommate's uncle's sister's husband saying he heard once of a co-worker's drinking buddy blaming some guy at the track's engine failure on it.

skinny z

And I too have yet to hear of somebody's brother's girlfriend's boss' cousin's roommate's uncle's sister's husband saying he heard once of a co-worker's drinking buddy blaming some guy at the track's engine failure on it.
That said, it was brought up in another forum by a professional engine builder although he too didn't elaborate.
Still investigating.
​​​​​​

skinny z

And this just in from Brian Shimkus at Melling:

The M-55 is the stock replacement pump for the SBC. GM lightened the casting many years ago. Melling uses the older more robust castings in the Melling Select pump line which is recommended for any performance or racing application. The Select series pumps also contain billet steel helical (SharkTooth) gears instead of the powder metal straight cut gears of the OE style M-55. There are 6 different Select series cast iron pumps ranging from the 10550ST to the 10555ST, each with different characteristics. The 10553ST is the M-55 equivalent, standard volume with a 5/8” inlet Melling Select oil pump. I’ve attached some early information about the Shark Tooth technology additional benefits as well as the flyer listing all and their characteristics.

I'd post the product details but the files are too large.

So, the M55 goes on the shelf and the new version gets ordered.
Just in case...

Fast355

iTrader: (2)

The M-Select version is cast thicker. That being said, get the M99HVS. That is the only pump I put in small blocks I build. I have used it for the past ~15 years in everything. I stopped using oil pump bolts as well after I found a couple of GM crate engines with the bolts GM supplied pushing on the rear main bearing. I use the ARP oil pump stud.

skinny z

I'll be sure to check further into that but at this stage of the game, delivery timing is everything. As it is this oil pump issue is going to set me back a couple of weeks. Any later than that I could well be dealing with freezing temps and snow. Seeing as I'm stuck working on an unsheltered pad in the side yard, I need to keep up the assembly and installation pace.
ARP stud already standing by ready for a pump...

sofakingdom

iTrader: (1)

I used to use the 99HVS alot also. It's actually a standard big block pump with a slightly higher pressure spring and a special screen to fit small block pans. It offers higher volume and pressure, but its main advantage is that the gears have more teeth, which leads to smoother operation and less spark scatter.

The Oil Pump Bolt Problem is notorious but poorly understood. All too often, during a rebuild, all the bolts get yanked out, piled up in a heap, cleaned, and put back in. It just so happens that the short head bolts are 7/16"-14 x 2"... the oil pump bolt is exactly the same as those in every way, except it's only 1-15/16" long. People who are careless often get them swapped. When that happens the bolt presses on the back of the main bearing, sometimes enough to wipe out the bearing and/or the crank. One of those "mystery" blowup causes that rarely is correctly diagnosed during the autopsy. Given the total HORSE PLOP I've seen from "rebuilt" GM engines, I'd guess they're as susceptible to sloppiness as anyone else, in this matter as well as plenty of others.



I forget where I got this image from... probably 20 yrs ago or more. This one maybe didn't blow all the way up, or maybe did, but clearly the bolt was pressing on the bearing and damaged the crank, which shed abuncha metal as can be plainly seen, and was therefore the wrong one.

Fast355

iTrader: (2)

This was a brand new GM L31 and a brand new ZZ4 I saw this on.

sofakingdom

iTrader: (1)

:shrug:

Obsolete engines, probably assembled by indentured underage conscript labor somewhere in the 3rd world like ... iunno, Illinois? Ontario? Florida? , ... I have no idea where. I guess anything can happen. And evidently it did. People accuse me of having a "trust problem", because I don't trust ANYBODY about ANYTHING. Maybe Skillet ran out of oil pump bolts and figured nobody would notice if he just used a head bolt instead: out the door, somebody else's problem. Maybe some bean counter decided the special bolt cost too much and the 2" one was 1/16" "better" anyway so they deleted the 1-15/16" part #. Maybe the last guy that knew about WHY that bolt was different retired, and n00b that replaced him had a kaizen, and this old weird bolt that nobody that was left knew anymore why it was different, all got thrown out and n00b got a bonus for reducing inventory to boot, so now they HAVE TO use the head bolt. Iunno, there's just SO MANY WAYS to screw stuff up, even something as basic and simple as that.

Humans.

NoEmissions84TA

iTrader: (1)

Images are from Grumpy's Performance Garage
skinny z - your new generic IS the stronger casting.

skinny z

Having worked in manufacturing, in an indirect way but direct enough to see how it often plays out, all of the above is true. And for as many decades as I've been in the game. which is many, I've watched it go sideways in a lot of different ways. (Try working in oil and gas in Alberta. It's incomprehensible!)
It snowballs when you relocate a factory from anywhere to anywhere and any level of continuity goes out the window.
This M55 fiasco came about innocently enough I suppose. The original version was robust enough to handle what the racing community was doing to the SBC. But then for reasons explained elsewhere, that robustness was all but eliminated as a cost saving measure. At least from my understanding. Then somewhere, someplace. somebody's brother's cousin....etc. had an issue and away we go.
Real or imagined, I'm going to side step the potential disaster. At this stage of game, as in money spent, what's another 100 bucks over the cost of the pump I won't use? 1% maybe? At least there's no additional labour to factor in. As I get older, the labour costs become more expensive.by whatever metric you want to use.
The engine is still on the stand.

skinny z

Unfortunately, that's my older generic pump. Over twenty years of service which sadly ended after ingesting a cam lobe and half a roller lifter. It's fubared.
Then the M55 thing came to light after my purchase.

skinny z

They wouldn't if a link bar rivet didn't let go. The roller went sideways and the rest is what you see. The lifter roller is an interesting sight as well.
But that bit of damage spelt the end for the otherwise wheezy shortblock. It needed a rebuild but i didn't think I'd have to fork out over $1500 USD for a cam and lifters. Although this time around I went with the best available and ordered a custom steel billet from Jones Cams along with his high zoot rollers. Plus a distributor gear to suit. $$$

Fast355

iTrader: (2)

I built a couple of 4.7L Dodge engines a decade ago. The 4.7L HO came with a forged crank. Someone at Dodge got a wild hair up their butt and superceeded the cast and forged crankshafts to the same part number. They are the same dimensions, so they should work right? Except it took the forged crank supply away. It took a helpful dealership ordering 15-20 crankshafts to find 2 that were forged for me. Any manufacturer/distributor is capable of incompetence.

I still cannot get a response from Spectra on this incompetence. They are building a condenser without building a mounting bracket. These idiot cost cutting bafoons walk among us daily!


As for the M55, I have seen a broken M55 casting take out a nice 406 myself when it broke in half. I saw Nissan do something similar on the VQ V6 oil pumps. They started making the pump hub gear out of garbage powdered metal. They would destroy themselves on 350Zs and G35s that were pushed often to redline. When I put timing chains in my G35, I changed the gear and it was a good decision because the OE gear had stress cracks forming in it.

skinny z

That you found a dealer that would do that for you deserves props on its own. That level of customer service also seems to have gone the way of the dinosaur. Summit went out of their way to facilitate a simple return (from Canada I should add). Carmen was immensely helpful.

Broken where? At the mounting boss (where it appears to have surrendered the most material)? Or split the sides where crappy castings often do?

Nutro

iTrader: (1)

Well I just installed a Summit branded (M55 embossed) oil pump kit but u sed the stock L98 oil pump bolt with copper gasket and skipped the stud. It's a stock motor though so hopefully all works well.

Fast355

iTrader: (2)

It sheared off in the neck, about 1" under the mounting bolt flange. It completely split in half and the pump fell into the pan. It broke in nearly the identical spot this pump did. I have seen multiple pictures of broken ones in the past decade, and they all break in about the same spot.

skinny z

That greatly reinforces my decision to get the select pump.
I had never heard of any problems in this regard. Then again, I wasn't looking. It only came up as part of a conversation about a different aspect of the M55 pump. I'm glad it did because I don't think that kind of failure has anything good come out of it.

Fast355

iTrader: (2)

Multiple people had failures back in the day with them. This is where I grabbed the example picture from. That is about the point I switched to the big block pump. The big block pump and pickup were cheaper than the M-Select pumps.

Melling oil pump m55(a) dangerous design change | NastyZ28.com

skinny z

I came across that thread as well as several others all from around the same year(s). 2006 or so.
And that fits in with what Melling had to say about the change "many years ago" and sofakingdom's comment about the early 2000's.
A Melling 10553ST should be on my doorstep before next weekend.




Then maybe, just maybe I'll get the engine stabbed in at last!