While it is true that the early version introduced in 1999 was often not well suited to high performance applications, the later version introduced in the 2006 Harley-Davidson Dyna model, and later incorporated in all Big Twins in the 2007 model year, was vastly improved The S&S Camshaft Gear Drive Kit 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 with the gear drive kit Popular camshaft grinds MR103, HP103, 635 H.O. now available for early Twin Cams Experience has shown that the new chain drive with hydraulic chain tensioners works well for all but the most demanding high performance applications The kit includes gear drive kit, gear cover gasket and cam bearings