Does the size of the pulley on a alternator make a difference?? I had one rebuilt and it has the wrong style pulley on it and the alternator
I took off is a different size pulley. It goes on a '64 283. I 've looked at 3 different alternators and they are all different.The GM number is 1100668 for the alternator. Thanks for any help

My car is strictly a street cruiser. I run electric fans etc...and have a sizeable electric load on my alternator. What I have found is I am better able to keep voltage up at idle and slow speed driving by running the smallest pulley available for my 94 amp SI12 alt. Lights stay brighter and my electric fan speed is higher at idle by turning the alt faster with the smaller pulley.
It was the guy at the alternator rebuild shop that suggested I do this. Maybe not good for racing though, the belt may come off a small pulley that much easier at high RPM.