To rebuild or replace...oil pump

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pishta

pishta

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Melling M72K (rebuild kit) is a buck less than the entire new M72 pump! Who rebuilds these things? And what does a bad pumps rotors look like, just worn gaps or grooves from injested crap?> I took my barnyard find 273's oil pump apart and saw some pretty good scoring on the tips of the 4 lobe inner rotor but the outer rotor looks perfect inside and out, and the .63 cent O-ring was rock hard and shrunk to expose 2 3mm gaps. I also noticed the outer rotor had coke at the base of each of its 'troughs', like the inner lobes never reached down there. I always just spent the money on new ones, just wondering how many I tossed that were still good enough? Not interested in HV model but I understand there was a kit that had extended rotors and cap back then too.
 
I rebuilt the pump in my 331 Hemi, but then they are almost impossible to find new.
 
I’ve got a brand new one 40$ shipped. It’s been sitting around for the last year doing nothing!

[FOR SALE] - New Melling M72 SB Oil Pump

Jake

pishta said:
Melling M72K (rebuild kit) is a buck less than the entire new M72 pump! Who rebuilds these things? And what does a bad pumps rotors look like, just worn gaps or grooves from injested crap?> I took my barnyard find 273's oil pump apart and saw some pretty good scoring on the tips of the 4 lobe inner rotor but the outer rotor looks perfect inside and out, and the .63 cent O-ring was rock hard and shrunk to expose 2 3mm gaps. I also noticed the outer rotor had coke at the base of each of its 'troughs', like the inner lobes never reached down there. I always just spent the money on new ones, just wondering how many I tossed that were still good enough? Not interested in HV model but I understand there was a kit that had extended rotors and cap back then too.
Click to expand...
 
You are right on the wear; it ususally shows on the tips and along the walls where the 2 moving parts pass each other. Any deep scores in the cover can leak pressure.

I rebuilt Opel 1.9L pumps because the pump housing was integrated in the timing cover housing which was expensive. A new gear set and pump cover would do wonders for oil pressure, even with some scoring in the soft aluminum housing, so I would expect similar results from your rebuild kit.

Anymore, I just replace if any question.... although I did reuse a Jeep 151 pump a while ago as it looked OK when inspected and the engine is not a performance engine by any stretch of the imagination. After reading someone here finding the relief valve inverted in a new one, I'l probably take even a new one apart for inspection.

(FWIW, I had Doug Dutra built me a /6 pump for stock use as he has the hardened gear for those.)
 
OK, found new one cheap locally, Ill save the rebuilding for the ol' hemi guys....:D
 
Anything that is common, just buy a new one, rebuild kits don’t tend to have warranties, new parts do.

I’ve rebuilt and shimmed a few common oil pumps, NOT worth the trouble. Buy new
 
I took apart a know good one out of my laid up stroker and the outer rotor is way closer than the old one, no slop at all and the inner rotor really snugs up against the outer in the lobes. I can now tell for sure that the old one is trash. My strokers had a few nice dings on the inner rotor but I cant see it doing any disservice to the pump in operation. IT does seem the older ones outer rotor wear into the pump body as its nice and shiny where the pressure side is.
 
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