Don Terrill’s Speed-Talk

I installed piston oilers in a big block chevy recently and while mocking up discovered that the oil pump shaft rubs the jet slightly. Can this be ground and polished for clearance or should the jet be trimmed back for clearance. It looks like .030-.040 needs to be removed from the shaft. The brass colored line on the shaft is where it rubs. It is a Melling select shaft that comes with the race series pumps if it makes any difference.

I've done it on a lathe without any issues.

consider: Heavy weight oil and / or Hi-volume pump put more stress on that shaft

SBC 400 takes basically the same size shaft, same OD, just shorter....and those are cut undersize to clear tha larger main bearing bore and don't have failure problems.

Anyone worried about a slight undercut on a Chevy oil pump drive shaft needs to take a look at the spindly little hex shaft in Ford V-8s and all your worries will go away about the Chevy shaft being weaker if you cut it.

The 400 SBc shaft is undercut for nearly 2/3 of it's length, with just 3/4" or so at each end left original size.

---back in the day when I was doing a lot of SBC & BBC engines I got to where one of the things I did was to machine the stock oil pump shaft with a recess in the shank--mainly just to get rid of 40 grams
---some of the oil pump shafts--maybe the SBC 400's---were machined for clearance maybe to clear the larger main bearing journals

---never had any problems with any of machined shafts--but I also have a shotpeener so I shotpeened the machined area---and made nice smooth large corner radius's where the shaft was machined smaller.

---I just used my lathe to machine the recess
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124/84* stock oil pump shaft / with a machined recess in the shank

* is gram weight

I was more concerned if the shaft was hardened and would have cut through the hardening, it was not. Started at .482 finished at .415 and polished on lathe with 600 grit, a SBC shaft is cut to .400 so there should be no ill effects.