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Larger pulley on 1 wire alternator

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Well, what's your question? Whether someone has changed a pulley or something else? I'm sure someone, somewhere, has changed one so I can make a wild stab in the dark and answer "yes" to your question.
 
Measure the bore of the pulley (or shaft), and then measure the current diameter of your pulley.

Now, let's say that you want it to run a desired rpm of 10,000rpm (x), and its turn off is currently at an rpm of 7,500rpm (y) on a 45mm diameter pulley and the calculated size of the pulley is (z), then calculate as this:

7500rpm = 10000rpm / (7500rpm / 45mm) = 60mm
or simply calculated as:
(x / y) * current diameter pulley = z ----- (10000 / 7500) * 45 = z = 60mm


With my Saturn alternator, which has a 17mm bore pulley, with a 4 rib 14mm belt, I purchased 63mm and 65mm pulleys. I have installed the 65mm pulley and it clears the oil pump sprocket pulley hump on the timing cover in a rear mount installation.

I purchased these from http://alternatorparts.com/
Part # 2482258 - 4-Groove Alternator Pulley For Denso 90-120A Alternators 14mm Belt x 65mm Rib OD x 17mm Bore
Part # 2481250 - 4-Groove Pulley For Hitachi and Mitsubishi Type Alternators - 14mm Belt x 63mm Rib OD x 17mm Bore

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I ended up with a 3.25" ford pulley that fit on well. I'll let you guys know the results when I get back on the dyno this week. It's already on and in the car so I might as well try it. The old pulley was 2 inches in diameter
 
It looks like I'm still having this issue. Any suggestions ?
 
I have huge grounds, and I'm not the only one having this issue. The larger pulley helped a little which would suggest that the alternator is the issue. Those gm alternators just aren't made to rev to the rpm I'm reving to. It's a one wire alternator so I know it's not wiring issue. It charges great up until about 7400 rpm
 
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