I was driving my car yesterday all is fine. I pulled it down to low, and buzzed it up about to hit 2nd and pop, car shut down. I thought I had a module fail. Well long story short, after pullin the cap between obsevations I relized the rotor had never turned durning my attempts. I pulled the Distributor and the shear pin had broken. The pump had locked up. I cant turn it to save my life. I never thought a oil pump could lock up, but it did. I had good oil pressure prior to this. I am guessing the gears broke and got binded up. Its a M55 standard volume and pressure. I seen some post about certain ones not to get put i have used this same style pump for as long as I can remember. I am not very clear on the melling pump problem. I know its something to due with a weaker housing. I guess anything is possible. Has anyone ever had such a problem. I am going to try and pull the pan today and see if there is anything other than my conclusion.

Are you saying that you took a large screwdriver, and inserted into the slot of the oil pump drive and it would not turn? or what?

Are you saying that you took a large screwdriver, and inserted into the slot of the oil pump drive and it would not turn? or what?

Before you go tearing things apart, make sure it was not the dist that locked. Be sure you check teeth on cam and dist gear.

I think it would have had to "eaten" something to lock-up. Let us know what you find.

Yeah I took a srewdrive to it. Its locked up. Something caused pump to locked up and shear the pin in Distributor gear. I will find out what happend to the pump as soon as I get around to pulling the pan off. Keeping my fingers crossed that its just pump failure. I have never had anything in my oil. I keep a close eye on the oil during changes by straining and checking every change due to cam failure paranoia. Only thing I can think of is my pick up came loose, and got tagged by the crank and broke off something , and then got picked up into the pump. I had a pick up come off before and it made noise at times, but i never heard a thing yesterday. After the first time one came off, I started tacking them and epoxy all around it. We shall see!

Depending on where your drain plug is , it is possiable to stick a long screwdriver thru that hole and get "just under your pickup" to help you satisfy your curosity before you pull pan. Do you have needle roller rockers? Any chance of you losing one needle roller?

I drained the oil and took a coat hanger and stuck it inside the drain hole and could feel the pick up in the bottom of the pan. So I took the pan off and looked for foreign metal in the pan and didnt see a thing. I took the oil pump apart and couldnt pull the gears out with a pair of pliers or turn them, so I drove them out. The gears was a little chewed up where something had passed, but there wasnt any one thing between the pump gears to have caused them to lock up. It looked like the gear was boogered up just enough to take up the tight clearance between the pump gears not allowing it to turn, IMO. I dont know how long the pick up has been off. I never noticed oil pressure dropping during stops, put then again the only time I do look at it is when I start it, WOT, and the ocassional clance. Oh yeah I didnt tack the pick up, put I did epoxy it. Hopefully the engine will be OK. I am going to pull some bearings and look later.

Mike strange issues for sure. I would think if the pick up had fallen off the pump completely while it was running you'd certainly have known it. The last SBC I torn down the pickup was loose and about to fall off, but had rotated until it hit the pan and that's as much as it moved. All I had to do was bump it and it fell out of the pump body.

If the M55 pump was purchased in the last ten years then it isn't really the same M55 pump that you've always run because it is the weaker casting. That's the problem when Mellings cast the weaker pumps that they say should never be used for performance engines they retained the same part numbers from the good Mellings pumps we used to run years ago. What you need today is the 10553 Mellings select series pump. It is the Select series high performance version replacement for the Z28 pump. Plus it has steel pinned gears and many other significant advantages. If you want a pump that you don't need to mess around brazing the pick up on then move into the 10552 select series pump. It has the bolt on pick up provisioning and it has 10% high volume output. I did not want the higher volume, but at least it isn't the 25% high volume that most are and it's the only way I could get the bolt on pick up was to move to one of the select series high volume pumps. Whatever you do stay far away from the Moroso blue printed pumps as Moroso is keeping quiet as to whether or not they accidentally used the weaker casting pumps in their blue print series, which their silence kind of points at the fact that they did because Moroso has always in the past been very good to respond to such questions.

Keep us posted on what you find. Really isn't anything inside these pumps that could cause them to sieze, but perhaps something moved through it that inhibited it long enough to cause the shear pin to break.

put I did epoxy it..

That might have been what came loose when the screen cam out and locked the pump up :( Have the new one tig welded in place.

I have only seen 1 Melling pump do this in 28 years of selling parts. When we took the pump apart we found a peice of wire brush between the gears. Found out the customer had recently changed intake gasket and used a wire wheel to clean gasket surface.

Mike strange issues for sure. I would think if the pick up had fallen off the pump completely while it was running you'd certainly have known it. The last SBC I torn down the pickup was loose and about to fall off, but had rotated until it hit the pan and that's as much as it moved. All I had to do was bump it and it fell out of the pump body.

If the M55 pump was purchased in the last ten years then it isn't really the same M55 pump that you've always run because it is the weaker casting. That's the problem when Mellings cast the weaker pumps that they say should never be used for performance engines they retained the same part numbers from the good Mellings pumps we used to run years ago. What you need today is the 10553 Mellings select series pump. It is the Select series high performance version replacement for the Z28 pump. Plus it has steel pinned gears and many other significant advantages. If you want a pump that you don't need to mess around brazing the pick up on then move into the 10552 select series pump. It has the bolt on pick up provisioning and it has 10% high volume output. I did not want the higher volume, but at least it isn't the 25% high volume that most are and it's the only way I could get the bolt on pick up was to move to one of the select series high volume pumps. Whatever you do stay far away from the Moroso blue printed pumps as Moroso is keeping quiet as to whether or not they accidentally used the weaker casting pumps in their blue print series, which their silence kind of points at the fact that they did because Moroso has always in the past been very good to respond to such questions.

Keep us posted on what you find. Really isn't anything inside these pumps that could cause them to sieze, but perhaps something moved through it that inhibited it long enough to cause the shear pin to break.


I agree 100% about the casting issues. I did a ton of research on the casting changes of the melling pumps and after seeing the little yellow slips that come in the M55, M55A, and M55HV boxes now. I knew I was definatly going to upgrade to an M-Select pump. There is a sticky thread on NastyZ28.com's forums about the design change and the problems it has caused many camaro owners like yourself. http://www.nastyz28.com/forum/showthread.php?t=65870
http://i23.photobucket.com/albums/b355/spoonlt1355/S3010016.jpg

I pulled the 8 rod cap and a main. The bearings looked good. I cant find anything. I did get a visual on the cam lobes and cylinders and all looks good! I am getting a select pump soon, then I can throw it back together. I havent looked into it, are these pump gears of a soft metal?

That might have been what came loose when the screen cam out and locked the pump up :( Have the new one tig welded in place.
I believe your right!

I pulled the 8 rod cap and a main. The bearings looked good. I cant find anything. I did get a visual on the cam lobes and cylinders and all looks good! I am getting a select pump soon, then I can throw it back together. I havent looked into it, are these pump gears of a soft metal?

Don't rush thru this, Use the select series pump, they do mention machined gears so I am thinking , hard metal. Go to the mellings site, there is information on select series pump. http://data.melling.com/Select/small_block_chevy.php

The pickup coming loose from the pump is a primary cause of oiling failure; if the pickup is gone, then the oil pump itself will not get oil and could cause the problem, but I'd be concerned also with the remainder of your engine also not seeing oil. Did you note the failure of oil pressure when you experienced the problem?

1) Dissassemble the new pump, and using a fine sandpaper, clear the burrs from the gears and inner housing. I also burnish the flats of the gears (that ride on the pump housing) and the housing/cover the same way using a piece of glass as a flat base. After that is done, and the housing/gears are cleaned, then rub 'molybdenum disulfide' grease on all 'metal to metal contact wear surfaces.
2) Braize the pickup tube to the pump cover, after fitting it for proper clearance to the pan bottom.
3) Reassemble the pump and use locktight on the screw threads and torque properly.
You will NEVER have any pump issues if you follow this process.

Mike if you don't want to mess around brazing the pickup on go with one of the 3 or 4 select series part number pumps that come with provisions for a bolt on pickup. Summit offers 3 different depth bolt on pickups for these pumps. Once you measure the depth of your pan you'll know which pickup to buy. The select series pumps come with hard steel gears and are deburred. The pump bodies to gears clearance is already reduced to minimize spark chatter from too much clearance in the body to gears. The gears both idler and drive gear are supported at each end with dowels unlike the standard pumps that are only supported at one end these dowels extend into the pump body to make it rigid. It has been posted by others that the Select series no longer uses steel gears, but mine certain had them after someone said they don't. Mellings also still advertises steel gears that are pinned and that's what I've found. I think you'd like the 10553, but I don't think it has bolt on pickup provisioning. The 10552 does and if the 10% high volume doesn't bother you and I don't think it will. Tim (wolf) on this site uses this pump as well and he is very picky about his lube system. I drilled my cap internal hex head capscrews that came on my pump to allow me to safety wire them with .032" stainless safety wire. They will never back out on their own now. It's an easy mod and I can walk you through how to correctly safety wire bolts if you haven't done this before.

I got the new pump on it and all is good! Thanks

Rather then brazing, I Drill and Tap through the Pickup Mounting Boss of the Pump and into the Pick Tube then thread in a Bolt, with a hole drilled horizontally through the head, cut to specific length as not to obstruct oil flow and Wire Lock it. I've never had a Pick Up tube fall out using this method.

I prefer the tall TRW Oil Pumps and use the same pump for both SB and BB Engines.