Hi, I am wondering what is the best size pulley to use on my 03 Cobra to gain HP but retain driveability? Also correct belt size for the pulley. Thanks!

 

No matter what you do to your Cobra as long as you don't do a head/cam package, it'll be 100% driveable on the street.

What kind of HP gains are you looking for? You can go to a 3.10 pulley which can run on your stock tune. Or you can go shorter to a 2.91, 2.81, 2.76.... The shorter the belt the more HP you'll make. But keep in mind, switching to a shorter pulley requires you to get the idlers so you won't shred and throw belts off everytime you go WOT. Also, you will need a tune. People suggest the 'canned' pulley tunes on handhelds are okay, but hardcore 03/04 owners will tell you to use the canned tune to get to the dyno only...

Also, when you swap pulleys, it's ESSENTIAL you get the upgraded heat exchanger, especially if you like to play at 100+mph on the highway. You'll be looking for a new shortblock before long if you don't keep the engine cool.