Alternator Voltage?

[Dane Brahler]

Sorry it took so long to get back on this thread, I got my mustang running again.
So the alternator was definitely to blame.
The part number I got was SUM-810301 , identical to the one in the OP
Summit racing could only give me 20% a new alternator since my warranty was up so $110 later I had a new one. I stuck with the same one this time. (and final time if this one dies)
With 4 ga wire at both the positive post and the ground post of the alternator i was pushing 13.8 volts at both the battery and alternator at idle.

 

[FastDriver]

i thought 2 1/2 " was stock

I measured an actual stock alternator pulley with a micrometer and got 2.17". So, I guess 2.25 with tolerance? I know that the mustang sites sell 2.5" alt pulleys as underdrive, and that the PA Performance 3Gs come with 2.25" pulleys.