6 1/2 wp pulley
 

Do i need to change my alt. belt? going from 7 1/2 to 6 1/2 wp pulley. no a/c

yes.

Absolutely, there's not nearly enough adjustment available to make up for the pulley diameter difference.

cool thanks. anyone have a size or part number?

You'll have to figure out the new length on your own.

I usually take an old belt and cut it to try to make up one that's close, then go to the parts store and get some help.

It might take a couple of tries to find the right belt that will adjust properly.