hey guys... where can i get smaller pullies for my whipple? and how do i know how much it will raise psi?

 

Give whipple a call. I got mine directly from them. My stock pulley was 4-3/8" in diameter so I got a 4-1/4" & a 4-1/8" just to see. I have only run the 4-1/4" so far. I believe they say that each 1/8" less in diameter equals 1 psi in boost.