WARNING: Never strike the ProCharger pulley with a hammer or other tool under any circumstance! Evidence of such force will void the warranty, as serious damage to the precision bearings within the ProCharger could occur.  

Let's take a eight rib pulley for an example.Figuring out sizes:

DP400I-08D -  This pulley is a 4.00 diameter size. The 08D means it is a eight rib. 

To determine the impeller speed, the following formula is used: 

Maximum impeller speed = crankshaft pulley diameter (N1) divided by supercharger pulley diameter (N2),multiplied by the step-up ratio (4.10 for the P-series/D series - 5.40 for the F series), multiplied by engine rpm at redline.

 How much boost the blower can produce depends on many variables: 

 * Cubic inch. The larger the engine the less boost it will make with a supercharger.

 * Headers and exhaust. A better flowing system will produce less boost, requires a smaller pulley to regain the loss in boost. Ultimately though, more power will be gained.

 * Camshaft and heads. A camshaft with some overlap will leak out some boost through the valves. Better flowing heads react a lot like a better flowing exhaust system.

 * Altitude. Elevation plays a big part in how much boost is produced. Those people living in the higher elevations have to spin the blower harder to see boost.

 * Condition of engine. An engine with real good sealing rings will ultimately produce more boost than one with worn rings.

 * Rpm. An engine that is spun up higher in the rpm range will normally produce more boost.

* Supercharger. A D-1SC will generally make more boost with any given pulley than a P-1SC will. The P & D series have a 4.10/1 gear ratio, the modern F series have a 5.40/1 gear ratio. An F-1A will generally make quite a bit more boost with any given pulley than a D-1SC will, partially as a result of the 5.40/1 gear ratio. 

When installing a new blower belt, don't go wide open throttle for the first hour as the belt needs to break in. Once the belt is broken in you will find that it has stretched, and it will then need to be tightened back down. Do this before going wide open throttle with a new belt, as once a belt slips it is more prone to slippage. Bob