1998-2002 LS1 F-Body Underdrive Pulleys

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.

Alt Pulley	Pulley Part #	AC Belt #	Access. Belt #
Overdrive	49-540120	11-378K4	11-755K6
Underdrive	49-540084	11-378K4	11-770K6
Stock	-	11-378K4	11-760K6

March Performance Pulley systems are designed to increase horsepower by reducing accessory drag on your motor. March's new LS1 dampener pulley has a fluid based center, which will not cause spark sensors to retard timing with resultant loss of power.  These pulleys have been dyno tested at 12 hp gain and are SFI approved.  A new harmonic balancer bolt is included and the two required belts are listed below.

SLP's new 25% underdrive balancer for LS1/LS6/LS2 Corvette's incorporates a number of high-quality features you won't find on any other aftermarket unit. Chief among them are a pair of extra-tall belt-retention walls that eliminate the belt-slippage issues common to other balancers (see photo). Gains of up to 10 horsepower can be expected. Other unique design strengths include 100% steel construction (other brands use steel and aluminum), integral timing marks, and built-in puller-mounting threads. Includes a new balancer bolt and detailed installation instructions. 

FEATURES:

• Extra-tall belt-retention "walls"--no more thrown belts!
• No aftermarket tensioner required
• 100% steel construction
• Lighter than the stock balancer
• Integral timing marks and puller-mounting threads
• Keyed for high-rpm or supercharged applications
• Does not cause false knock retard or erratic power-curve dips
• Includes a new balancer bolt
• SFI Approved

The TCI® Elastomer Balancer incorporates a super strong billet steel inertia ring for longer life and better performance. The high quality bonded rubber eliminates outer ring movement, eliminating a traditional weakness of previous elastomer balancers. For anyone needing an SFI tested and approved balancer, the TCI® Elastomer Balancer, capable of handling 12,000 rpm, is the answer.

Features & Benefits:
• Incorporates a super strong billet steel inertia ring for longer life and better performance
• High quality bonded rubber eliminates outer ring movement
• SFI tested and approved elastomer balancer capable of 12,000 rpm