Great kit if upgrading an engine that already has S&S gear drive camshafts already installed Reuse existing outer gear drive 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 reverses the rear cam's direction of rotation, providing additional operating clearance between cam lobes As a result, higher cam lifts are possible with the gear drive kit Camshaft set is designed as bolt in camshafts, for 88", 95", and 96" with compression under 9.7:1, great RPM range from 3000-5500 rpm