Hey guys I have 8 rip pulleys and I'm currently using the belt that came with the supercharger which I'm not sure the size of it, I'm running 3-3/8" supercharger pulley with 7" underdrive pulley and I just got 2-3/8" pulley and I'm wondering what belt size I should use for the 2-3/8" ? I tried to reach KB they are not answering and I'm leaving the country in like 3 days and I need to get the belt ASAP, if you also can provide me with manufacturer name and part number that would be great. If I can recall i think KB use Dayco.

If the belt you currently have fits take it off and measure it. Or take it to the parts store and compare. Then just find the correct length in an 8 rib.

the car is overseas and I need to bring the belt with me from here instead of going back doing all that and pay expensive shipping

Do you have any kind of adjustment for your belt length with your pulley set up? My twin screw has a pulley that can adjust a bit for belt length. Anyways, just do the math. 3 3/8 pulley circ is about 10.6 2 3/8 pulley circ is about 7.46 circumference difference is 3.14 or pi since we're dealing with an even inch difference in diameter. Figure out your belt wrap around that pulley, lets just say it's 55%. Take 55% of the difference in pulley circumference and that should give you the difference in belt size.

I found out the size of the belt that I have 122.3" and I went an inch shorter 121.3" since the new pulley is an inch smaller , from NAPA and I believe my KB kit came with that adjustable pulley so I can play around the tightness a little. Thank you