Pully for 3G alt swap

ForceFed70

That's why they call it "dope"
Founding Member
Dec 6, 1999
4,818
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BC Canada
Where did you guys get the v-groove pully from? My stock pully is the wrong size (shaft size is too small) and all of the 3G alts in the junk yard had a 6 or 8 rib pully.

Thanks!
 
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Any good machine shop should be able to open up the stocker to the right dia.

Or most of the pulley companies (march, etc...) should have one that will work.

Just measure the stock pulley and use that measurement to get the right one.
(down in the grove, the outside dia is irrelevant... although larger o.d. is better for anti-flyoff at high rpm)

When in doubt you can go slightly larger to slow the alt and free up a little bit of power: ala - underdrive pullies
( a 3g alt will probably make more power at idle than your stock alt did at redline :rlaugh: )
 
How many amps is the 3G alt you plan on using?

I got the pulley with my alt from these guys:

RJM Injection Tech Alternator Accessories & Parts

I have a a serpentine setup, but they also sell a dual V-groove because it will slip with a single belt if the alt is over 100Amps. (mine did - when I had a 130A 3G)

3Gpulley.jpg
 
Picked up my dual v pulley from a local Napa auto store and had the old one removed at a local Kragens since they had an impact wrench...then put the new one one had them tighten it and then retest the alternator.

Marc Cramer

Did you specify a make/model/year, or better yet do you know a part #? The NAPA guys in my neck of the woods are useless unless you know the part# or can tell them exactly what year and engine combo of the vehicle it came stock on.

Thanks.