what size fan belts for my a/c alternator pulley

[Lloyd Hammond]

Need to change my very old fan belts on my 383 with a/c and p/s. The two fan belts that work the factory a/c and alternator are Gates 7650 XL, which are supposed to be 65" circumference and 10mm (~3/8") wide. The factory specs say the belts should be around 64.5", so close. My alternator is all the way over toward the firewall suggesting the belts are far too long. I feel they could almost be 10" shorter. What belts are people running (lengthwise)?

Thanks in advance.

 

[pnora]

Gates 7640

 

[AR67GTX]

10” shorter is a lot to go shorter. Move the alternator back to where you would like it to set, pinch up the slack on one of your old belts and put a mark on both sides where it’s pinched together with a marker, measure the distance between the two marks and subtract that off your old belts dimension. Don’t go too short or you may not be able to get the new belt on to the pulleys.

 

[pnora]

What pulley is on your alternator? If the alternator has been replaced it could have a smaller diameter pulley. That would make sense that you are at the end of your adjustment with what seem to be the correct belts..