In order to choose the best performance pulley kit for your vehicle, you must make some decisions. The most major decision is the intended use of the vehicle. For any vehicle that will be driven on the street, a performance pulley kit that reduces the vehicle's charging ability may not be a wise choice. This can also be a factor to consider when slowing down the engine's water pump, which might result in over-heating. For an off-road or competition vehicle, these are commonly not factors that will enter into the decision. For these type of vehicles, the amount of speed reduced at the engine accessory level can often be a horsepower-increasing function.
A performance pulley kit consists of different-sized engine accessory drive pulleys that actually reduce the speed of the accessories as compared to the original manufacturer's provided drive pulleys. By slowing the accessory drive speed, engine horsepower is increased -- often greatly --, giving the vehicle better performance. It is necessary, however, to identify the amount of performance needed prior to purchasing the performance pulley kit. Some pulley kits also eliminate air conditioning compressors, power-steering pumps as well as smog pumps. Attempting to install the wrong kit on a street-driven car could potentially create a possible illegal vehicle and result in ticket, fines and the restriction of the vehicle from public streets.
The type of kit that is to be purchased is the next area of consideration. Inexpensive kits are often sold with lightweight, stamped-steel pulleys. These pulleys are fine for a low-performance vehicle that will see only minimal use; however, for any high-performance vehicle that will see more than occasional use, you want to choose a kit that includes cast or forged aluminum pulleys. These performance pulley kit pieces will often give less wobble and also withstand higher engine speeds without breaking apart or exploding under stress.
For an engine that requires the traditional V-belt, a performance pulley kit with extra deep grooves will aid in the belts being thrown off the pulley due to high engine speed. A shallow V groove will often allow the belt to ride up and off or out of the pulleys when at wide open throttle. Modern performance pulley kit components designed to work with a single serpentine belt are also available with slightly raised edges to prevent the belt from coming off at high speeds.