Need a quick favor

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Hey Jason-

I don't know if my pulley is OEM since my car came with underdrive pulleys on it already. But anyway, the pic shows my dimensions.

FWIW- when I got a new alternator a year and a half ago, the replacement alternator came with a new pulley. It was larger than this one, so I had it swapped. It makes me think that my pulley is a overdrive model.

Which dimension is the 'advertised' dimension between the 2? I mean, you always hear 1 size listed when a pulley is advertised.



  • alternator pulley size.jpg
    alternator pulley size.jpg
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to check for pulleys: Drive the car so its warm, then park it in idle and leave it for a while with the headlights, ac, and stereo on. If you're voltage isn't near the M or the A in NORMAL on the guage, then congratulations, freeeee mod.
well it is stock i guess. it is 2 11/32 or 59 mm, but when i was going to order the overdrive alt. pulley. It is 59 mm as well. So much for that. is there a vehicle anyone knows of that has a smaller alt pulley that will work on our cars alternator, or am i gonna have to buy another alternator. I had a mean grean sold it, buddy needed it for his race car, and i didn't think it was doing anything. Now when my factory fan kicks on the voltage surg is causing my idle to be affected. idles wonderful as long as the fan doesn't come on.

someone help


and the alt on the car now is newly rebuilt as was the original but i rebuilt it before i put it back on, and sold the other one. So the alt is charging good
You want a larger alternator pulley to see a performance gain. A smaller pulley will spin the alternator faster, resulting in more parasitic loss. You want to slow the alternator down to reduce the drag.
Dan, I think Jason was looking for a charging gain at the expense of performance.

Jason, I thought that overdrive pulley from PPI was a 56mm.

And what is the dimension are pulleys are advertised at? Is the pulley in my drawing above considered a 59mm or a 55mm? Would that make the 56mm PPI pulley smaller or bigger?

ok, i'm really confused now, i measured mine and its only 2 inches in diameter. i know the previous owner put underdrive pulleys but do they have a smaller alt pulley to make up for the bigger crank pulley?
no they don't have a smaller pulley. I want the overdriven pulley, i may have read the other ad wrong on their site. I will double check. you prolly already have the overdrive pulley fiveohh.

i will post the size on the web site in a minute


ps.. rick , i hope i was wrong because this **** is killing me. My car idles puerfect until, the fan kicks on.............anyone have any other ideas. TPS and IAC motor are new.


do i have a ****ty wire system or need more volts at idle or what. I am gonna have the alt checked just to make sure in a couple days