How to measure supercharger pulley?

[jack]

Do you measure the pulley on the inside or outside of the groove. Just bought a

03 and would like to know which pulley it has. Also found a pulley in the

trunk that has #309155e&c on it and it has never been used. It measures over 3

1/4 inches. Thanks for the help

[ausie]

Actually there are two pullies for which you can alter the speed of the supercharger. The obvious is the one on the supercharger, but you can also change the belt speed by changing the pulley attached to the crank. If you could measure both just take the average of the two. More than likely the outside or raised area of the groove will be the number you want.