Pulleys in general are round thingys that spin and do "work". The classic example are trams that are pulled by cable.
The pulleys you are referring to is a crank pulley, which goes at the end of the crankshaft. It sits all the way at the bottom of the block. There's already one on the car. It is part of the system of belts and pulleys that drives the alternator, air conditioning, and power steering. Part of the stock pulley is the harmonic balancer, a rubber grommet designed to reduce crankshaft vibration.
After market pulleys are lightened and smaller in size. They are commonly called underdrive crank pulleys or lightened crank pulleys. Both the reduced weight and underdriving caused by the smaller size are capable of producing power gains. However, aftermarket pulleys do not have harmonic balancers, and according to some, it can lead to engine damage.
For more details and FAQs, go to http://www.unorthodoxracing.com
_________________
Jeff - SXV10
All Show + No Go = Drive Slow
Pictures Mods List
<font size=-1>[ This Message was edited by: SpectraBlueCam on 2002-05-16 10:56 ]</font>