509." valve lift. IOG = gear drive cams with Inner & Outer drive Gears. Complete kit with installation hardware; bearings and gasket. Bolt-in; high torque from idle to 4000 RPM for 88" engines with stock compression. The gear drive system is in fact a revolutionary different and much more reliable construction. Especially in high lift/performance applications; when compared with the OEM chain-drive design. A gear driven camshaft is stronger and will not give any of the mechanical problems connected with the OEM chain driven camshafts. The S&S gear drive kit will increase valve timing accuracy; and therefore horsepower; by eliminating the timing chain lash and loosely fit stock cam gears. The only downside of gear drive is that you may experience a slight increase in mechanical sound; this is why OEM is using a chain. It has no other mechanical advantages whatsoever. Since the chain guides and tensioner are eliminated there is no longer the possibility for these parts to fail and damage other engine parts. The S&S gear drive kit reverses the direction of rotation of the rear cam; providing additional operating clearance between cam lobes. As a result; higher cam lifts are possible with the S&S gear driven cams. Note: With the exception of the 475G and 510G cam; adjustable pushrods (like MCS 503573) are required to compensate for the smaller camshaft base circle of these cams. Note: Material may have to be removed from the inner surface of the OEM gear cover before in