47 oil pump

[Tom P.]

Hello all.I'm new to the forum,been an AMCA member for a year.
Can anyone tell me the proper o.d. for the late cast iron oil pump plunger and/or the correct clearance in the pump body?And the same for the return gear drive shaft?
Thanks
Tom
P.S.-I ride a '47 chief

[brian_groff]

Plunger Clearance

Was cruisin' through some messages and saw your question...though you've probably already gotten it answered.

Clearance should be 0.0005-0.0015 for maximum performance. It doesn't really matter what the correct bore size is if you've got clearance correct. A good fix is to hard-chrome the plunger and grind it to spec.

[Tom P.]

Brian-Thanks for the reply.I did get an answer earlier ,but it isn't the same as yours.Rocky Halter miced up some NOS pumps for me an found a lot looser fit.
Do you mind telling me where your info is from?I get paranoid about things like this!
Thanks Tom P.

[brian_groff]

I did it to a friend's oil pump and it worked fantastic. Guessed on the clearance. Figure it's gotta be small enough to stop any wet sumping from occuring while the bike is parked.

[Tom P.]

Thanks Brian-I went back and checked my notes and Rocky's dimensions aren't that much diferent from yours after all-in fact there is some overlap.
Thanks again for the reply
Tom