So I know many forums have debated the living crud out of this topic. THe short of it is. Melling back in 2004 started messing with the castings and gears of the tried and trued M55 Oil pump that was just about universally good in every application. The original design had billet gears and a thicker casting. The new designs had a thinner casting and Powder metal gears. They got enough negative press they changed back the casting or they say they did, but people are finding it is still a crap shoot on the gears, and Melling is saying if you want to be safe you need to use their select series pumps, that are about 80 dollars more and have also had reports of shipping with wrong gears or even worse bad bolts holding them together.

Here is my delima I have one of the old school M55 pumps from the motor I just tore down. This pump was blue printed and ported by me, and ran 40psi at idle and 60 psi at full tilt in my old motor. Even still has the made in the USA label on the casting that the new ones don't because of the obvious reason.


Used to be standard practice to run down to the parts store and get a new pump when doing a build, but with all that has happened, I am seriously thinking of stay with my known quantity. Not to mention it is already setup for my trap door oil pan. What do you guys think???

 

Definitely keep your old one!
Unless it has seen some sort of abuse/damage, then there's nothing wrong with it. You said you already blueprinted it, so a quick inspection should be enough.

 

Melling still makes their pumps with a strong casting and some other improvements over the M55, but its under the melling select/performance line (M-1055x). Theyre expensive as you said, though. I paid like $70 for mine. The quality was pretty good, but it does make one question why they would do it in the first place. My old M55 HV that came with my goodwrench had powdered metal gears, if I recall. The select has hardened steel.

If the current one's gears look good and the cover and case arent scored, then its still good.

 

Well I have one word for the Melling Debacle "MILODON!"

After doing some searching, viewing at parts stores, and a couple phone calls, seems this is a pretty good replacement for the ole M55A. Evidently Milodon does there own castings and they must really care because I think the casting quality is down right outstanding. The pump looks like it has been tumbled before it was machined. To top it all off I got one at Winners Circle for 32 dollars which is half of what they want for a Mellings Select, which only seems to come in "rediculous pickup size" or "suck your pan dry"

Here is the original good M55


The Milodon


Here is the two side by side


Notice how smooth the outlet is.


No way to really tell what the gears are made of, but they look like pretty hard stuff. There are no casted in marks and they do not absorb marker. All these things on other sites supposedly point to billet gears. At any rate i feel comfortable.

 

I know welding on a pickup is kind of contversial but I have always had luck with it, and I have a method. I take all of the devices out of the cab. Then clean it really well. I press the pickup in according to the height determined from fitting it to the installed pan, then I make a quick tac to keep the temp down and throw a heavy oily towel on it to cool it down. Then clean it all.


Since I had the spring out I went ahead and measured its force since I had the spring force measuring device out for building the heads. The Milodon came with a 5lb/in spring, the yellow one. I pulled the spring out of my old pump, it was 7lb/in, and since I like the pressure in my old motor it got the nod for reassembly. I put a little synthetic grease in the pump gears put the spring in and locktighted the bolts down.


Speedway motors had these deadsoft copper gakets for the oilpump for $9. I figured it couldn't hurt


It does not look like anything fancy, but I am feeling pretty good about this setup. I think it should do as god or better than my last motor and I think I will be able to rest easy knowing I do not have a chinese reject pump made by a bunch of gosh darn penny pinchers.






Here is my pan, It has always been good at keeping the oil in the pump in the past so it is moving on to my new motor.

 

I think thats a newer style pump for them, isnt it? No doubt to capture the market that Melling left when they went to their crap base-line pumps.

Casting looks real clean on it.

 

Not sure if it is newer or not. I have scene older reviews were people had some stuff to say about the roughness of the casting, and they had a clocking issue for a while, but some in their product development must of been listening cause this pump seems void of any defects. At 32 dollars they have my vote everytime. This will be my new go to.