Over drive alternator pulley- need shorter belt?

[DPGDirk]

Hey guys, doing a new 140amp alternator with my fan swap and using the smaller overdrive pulley from LS1fans .com.

Will I need a shorter belt?

I've heard it both ways...

Thanks!

 

[Rocket Man]

I used their overdrive pulley on my '02 Denali with it's stock 130 amp alternator and the stock belt is fine.