W Body Store

What Size Pulley Can I Run

If you have you have a supercharged W Body you've almost certainly been tempted to swap your stock pulley for a smaller unit. After all, this is the easiest way to make power on the supercharged cars. Unfortunately it's also the easiest way to blow your engine if proper pre-cautions are not taken.

This brief article will discuss what it takes to run each specific pulley. This article should be used as a reference only. You should always scan for knock after switching to a smaller supercharger pulley. Click here for more information on knock.

Your vehicle is equipped with a 3.8" supercharger pulley stock. The one exception to this rule is a limited amount of SLP branded Grand Prix GTXs and Regal GSXs which were equipped with a 3.5" pulley as an option. Your vehicle will make about 6lbs of boost with the stock pulley depending on weather conditions.

This guide makes the following assumptions:

  • You're driving a 1997 - 2007 Vehicle with the Series II/ III Supercharged Engine
  • You're not running a converted L36/Topswap
  • You're running a Gen III Eaton M90 Blower (add .10") to each listed size if you're running a 2004+ Grand Prix

For each .10" in pulley size you go down you will generally pick up 1lb of boost.

Core Modifications (3.5" - 3.4") - The following modifications should be present when any pulley smaller than stock is being used.  They will also allow most vehicles to run a 3.5 - 3.4" pulley with no knock:

3.3" - 3.2" - In addition to the modifications above:

  • Ported Manifolds
  • Headers (Instead of a downpipe & ported manifolds)
  • Rockers (1.9 ratio)
  • Mild Cam (Instead of rockers)
  • Intercooler (Instead or in addition to rockers/ cam)

3.1" - 3.0" - In addition to the Core Modifications:

  • Cam
  • Intercooler (Instead of in addition to rockers/ cam)
  • Headers (Not absolutely Necessary but strongly recommended)
  • Injectors (42.5lbs/ May not be necessary; depends on scanning)

2.9" - 2.6" - In addition to the Core Modifications:

  • More aggressive cam or mild cam & mild rockers
  • Intercooler
  • Injectors

We take no responsibility for any engine failures as a result of advice garnered through this article. A responsible owner will always scan for knock after changing their supercharger pulley.

Happy modding!