Designed for 88" to 103" CID engines with compression ratios between 9:1 and 10:1. Strongest from 3200-3700 rpm. Increases valve timing accuracy by eliminating timing chain lash and loosely fit stock chain drive. Reverses the rear cam's direction of rotation, providing additional operating clearance between cam lobes resulting in higher cam lifts. Material must be removed from inner surface of stock gear cover to install. A hydraulic press and other professional level tools required to install kit. S&S recommends that adjustable pushrod/cover kit be used. Cam bearings and gasket must be replaced when installing new cams. Kit includes camshafts, gearcover gasket, bearings, oil passage block off kit, retaining ring, o-ring, inner and outer gears. Made in the USA. Due to the inherent characteristics of gear drives, you may experience more valve train noise.. Installer must check coil bind, valve to valve clearance and valve to piston clearance..