Comes with camshafts and inner and outer gears, this is a complete kit Fuel injection tuning required. Pinion shaft run-out must be checked before installing S&S Cycle gear drive cams. A hydraulic press and other professional tools are required to installS&S Cycle gear drive cams. Additionally, material must be removed from the inner surface of the stock gearcover. The stock crankcase may require clearancing for S&S Cycle .625", .640", and .675" lift cams. S&S Cycle recommends that gear drive cams be installed by a professional mechanic. Due to the inheraent characteristics of gear drives, you may experience more valve train noise with gear driven cams. Oversized and undersized gears are available to help achieve correct gear lash. S&S Cycle have found that with 160 lb. of valve seat force, the S&S Cycle gear drive cams will perform well up to 6200 rpm. If higher rpm is anticipated, valve springs that provide higher seat force should be used. Camshafts that exceed the limits of the stock valve springs require the use of special high lift springs. Most S&S cams have higher lift than stock and are designed to take advantage of the extra flow of ported stock heads or S&S Cycle Super Stock heads. Due to the high lift of these cams,S&S Cycle adjustable pushrods are recommended. To get the best performance from a performance cam installation, a high flow intake and exhaust system is also recommended. Quick installation and Easy Start Cams allow stock starter to start any engine. Kit contains cams, gearcover gasket, cam bearings, and instructions. 1999-2004 stock springs will handle camshafts with lift up to 0.510". If a camshaft with higher lift is installed, high performance valve springs capable of handling a greater lift must be used. 2005-up stock valve springs will handle camshafts with lift up to 0.585". If a camshaft with higher lift is installed, high performance valve springs capable of handling a greater lift must be used. Cams with over 0.585" of lift will cause interference between the valve spring top collar and the valve seal with stock cylinder heads. Installation of S&S chain drive cams requires special tools. Attempting the cam change operation without these tools will be difficult. Damage can result which will not be covered under warranty HP103 Camshafts are designed as bolt in cams for engines with 103 and stock 9.7:1 compression up to 10.5:1. Works well with stock, un-ported heads, but is great for S&S CNC ported heads. Best power in the higher rpm range, 3000-6000 rpm. Bolt-in.