Great kit if upgrading an engine that already has S&S gear drive camshafts already installed Reuse existing outer gear drive gears The S&S Camshaft Gear Drive increases valve timing accuracy by eliminating timing chain lash and the loosely fit stock cam gears This is accomplished by replacing the stock cam drive sprockets and chain with light press fit S&S gears Because the chain, chain guides, and tensioner are eliminated, there is no longer a possibility for these parts to fail and damage other parts The S&S Camshaft Gear Drive Kit reverses the rear cam's direction of rotation, providing additional operating clearance between cam lobes As a result, higher cam lifts are possible Designed for 88"-95" engines with 9.7:1 compression ratios and 100"-124" engines with 9:1-10:1 compression ratios Massive horsepower and torque starting at 3000rpm 88"-103" rpm range 3000-6000, larger engines 2500-5500 rpm