Established in 1998, China Xiaowei Bearing Co., Ltd. is a high-tech enterprise specializing in asp pulley manufacturer and design many kinds of bearings. We have a modernized staffs of tech research and fog machine development, ISO9001 certificated, and manufacturing adopts advanced domestic and foreign standards such as GB, API, JIS, DIN, BS, NF and ANSI.

What do Underdrive Pulleys do? Underdrive pulley systems increase engine horsepower by reducing the amount of power required to drive external engine accessories. For example, the alternator, power steering, water pump and air compressor rob horsepower from the engine. By replacing factory-sized crank and accessory drive pulleys with a resized pulley, the accessories are slowed, resulting in more horsepower available to the drive wheels. Typically, a set of Auto Specialties street pulleys will increase horsepower by 12-15, and increase mileage by 2 to 3 MPG. All pulleys are manufactured from Billet Steel or Aluminum, exceeding factory quality.
ASP LS1 underdrive pulley kit reduces parasitic power losses associated with high accessory speeds, freeing up additional HP. It also reduces the rotating inertia on the front of the crankshaft allowing for faster revving. We have seen just over 13 rear wheel hp increase with this kit installed on stock LS1s.

ASP's 25% underdrive crank pulleys for the 5.7L LS1 F-body (Camaro and Firebird)& Corvette and 5.3L GM Trucks incorporate a new harmonic balancer in their design.Typical gains are up to .1 in the quarter mile!It is required that you change both the AC and the Accessory belts when you upgrade to this pulley; belts are listed below.Thunder Racing also includes a new factory harmonic balancer bolt with the purchase of an LS1 Pulley.You can also upgrade to a ARP Harmonic Balancer bolt, which is re-useable (listed separately.)
When purchasing an ASP underdrive crank pulley, there are three options for alternator pulley selection:Stock Alternator Pulley - Most commonly used.Suitable for most applications.
Overdrive Alternator Pulley - Recommended for automatic cars to help bring alternator speeds back to near stock levels without sacrificing too much horsepower.Extremely important for vehicles with high accessory drag such as cars with lots of stereo modifications.Underdrive Alternator Pulley - Recommended mainly for track use.Not recommended for daily street use due to low alternator charging.