You guys that build engines frequently- inspecting my old 260 V8 Mercury oil pump, clearances were surprisingly not too bad, but major scoring on the cover and rotors. Is this amount of scoring “normal” or “jeez, I’m surprised it ran”. Oil pressure on engine before it was pulled was low, but not non existent. I have a new Melling pump to install, just inspecting this old one out of curiosity.
you can still see machining marks over part of the worn area, so the wear really isn't very much. I'd put it back in if it only had to last 25k more miles. Which describes 99.5% of the old engines we work on.
I’d run it. If you were really concerned with the cover, a piece of gl*** and some 320 wet/dry sandpaper and it would be fine.
I already have a new Melling to replace this one. I was just curious as the scoring looked excessive for a pump that the clearances were still spot on where they should be.
Those gerotor pumps lose efficiency through tip clearance/scoring/wear and the same in the end plate area. Possibly relief poppet or seat. Scoring is generally a product of contamination in the oil , if the clearances are correct,, or clearances to tight or running dry, low oil or blocked suction screen. As said,,Cleaned up and a bit of a lap and it’ll probably be fine. Not a high pressure system . As you know, your low oil pressure could be other worn clearances in your engine.
Good used part in my opinion, you say that you have a replacement pump already, I’d be cleaning up the old one and putting it aside, these days the state of new parts being questionable, you just never know
A good friend just replaced a brand new melling pump in his new nailhead motor. It lost oil pressure just after break in due to a chip in the pressure relief ball seat area.
That looks like an iron housing. I've only seen aluminium factory ones in SBFs. As a side note, time has taught me that aftermarket replacement parts are rarely ever as good as factory parts.
I did this on the 58 Cad oil pump, also got rid of the Vac off the base of it. I brought a new kit for it , gear set,poppet ,spring and gasket, lapped the poppet in and it was good to go. [QUOTE="X38, post: 15076248, member: 5183" As a side note, time has taught me that aftermarket replacement parts are rarely ever as good as factory parts.[/QUOTE] Same thoughts myself, the Cad pump body was good so replaced the gears, one with new shaft,,flipped the end plate and worked well.
The engine was rebuilt around 1980. Very possible this is an aftermarket pump from that era. Also, I found out the cover on this one can’t be flipped, as the holes are all slightly offset, so it can only be installed ONE way. Sounds like an aftermarket manufacturers attempt to avoid people flipping the cover over!
More likely the 1 o’clock hold is offset to allow clearance for what looks to be the dowel hole next to it. Check the side clearance on the gerotor elements. I would bet on lack of lubricant due to inadequate side clearance. There’s not much of a hydrodynamic film, with the sliding motion and sharp edge, unlike a journal bearing.
When trying to prelube my buddy’s Ford prior to the first fire up, it was locked up tight. The new Melling pump had enough trash in the impeller to prevent it from turning. It could have been a disaster if we hadn’t discovered it first.
It’s a good idea to dis***emble every new oil pump and inspect for debris. I also dis***emble new oil pumps to pre-lube them with Lubriplate 105. It prevents dry starts and aids in priming the pump.
Interesting. I installed a new Melling one recently, but I always open them up and clean them first, to be sure. As you proved, it is a good practice because you never know.
I was taught to open them up while in HS auto shop. Never a disappointment, I have yet to see one without some crud in them. Mostly embedded in the ***embly lube.
The Jalopy Journal
