Under-Drive Pulleys
 

While at a garage today replacing a stripped oil-pan bolt the tech told me that my serpentine belt is on its way out. So I thought to myself what an awsome time to sneak in some performance parts. But heres my question:

If I were to buy a Under-Drive Pulley Kit would the replacement belt just be a regular GM type? Or is it anything special?

Obviously the pulleys would be put on at the same time as the belt.

The new belt you can get at any parts store, you just need to know what size to get.

Depending on the pulleys you get, you can run a string or something to get the approximate size you need. I believe the two piece March underdrive setup (Alternator/Crank) requires a 59 inch belt. SO you would need Dayco number 590K6.
590 = 59.0 inches k6=6 rib

If you just get the March crank pulley only, then I think its a 59.5 inch belt. So 595K6 would be the Dayco part number on that.

those are old dayco numbers as far as i know, at my work its 50xxxxx...5060590 would be 6 groove 59 inch belt...5060595 would be 59.5...5070590 would be 7 groove 59 inch.. and so on

save your money and get a stock pulley, underdrive pulleys are worthless

I'm actually with him, all i noticed on my 91 was that my lights dimmed at a stop with my radio cranked.

i have em and havent noticed any loss in charging power and the motor seems to spin up a lil quicker

I am also agaisnt them. Waste of time money and effort. The 200 or whatever could be spent on something else, or save it and spend it on something later on.

i paid less than 100 for a used set in mint condition and they came with a belt in great shape