I know that this question has probably been asked already but I missed it! So I was doing a little reading the other day and read up on underdrive pully's and how they are supposed to do some pretty good things to an engine. I realize that there is alot of sales techniques involved when companies are trying to sell products so I was hoping that someone has one installed and could fill me in on the ups and downs! Thank you,

Paul.

Underdrive pulleys definately work, it's basic physics. Using a smaller diameter pulley robs less horsepower that the factory pulley.

One tip, make sure you change the alternator pulley to a larger diameter tyo speed it up, so you don't lose any charging ability.

We typically see 10 RWHP with the addition of underdrive pulley sets.

Ed

Pain in the butt to install. I did mine while doing my heads and cam. It does free up some additional horsepower.