S&S 640G Gear Drive Camshaft Kit Fits Harley Big Twin 1999-2006

Weight: 5.82 Application Information for S&S ® Camshaft for 1999-Later Big Twins S&S offers a variety of cam grinds for 1999-Later Big Twin gear drive engines. With the exception of the "bolt in" 510G camshafts, S&S cams are high lift and were designed to take advantage of the extra flow of ported stock heads or S&S Super Stock ® cylinder heads. Due to the high lift of these cams, S&S adjustable pushrods and high performance valve springs are recommended. 510G: Designed as a bolt in cam for 88", 95", & 96" engines with compression ratios below 9.7:1. Intended primarily for stock heads that have not been ported. 546G: This is a short duration emissions cam with very little overlap to reduce emissions of unburned hydrocabons. It is intended as a replacement part for S&S emissions certified engines. 570G: Designed for 88" to 96" engines with compression ratios between 9:1 and 10:1. 585G: Designed for 88" to 95" engines with compression ratios from 10 to 10.5:1 and 100" and 107" engines at 9.7:1 to 10.5:1 compression. 625G: Cam set designed for 95" or larger engines with compression ratios between 10.0 and 10.75:1. 640G: Designed for engines of 95" or more with compression ratios between 10.5:1 and 11.5:1 used in S&S 124" engines. 675G: Designed for 120" or larger engines with at least 11:1 compression ratio. The patented S&S Gear Drive Cams are a must in order to achieve the full potential from high performance Harley Davidson ® Twin Cam 88 ® engines. Since the chain drive system used in stock Twin Cam 88 engines is not adequate to accurately control valve action at high RPM when using high lift cams and high performance valve springs, a different system was needed. The S&S Gear Drive System was developed to improve performance and to eliminate potential engine damage caused by failure of the chain and tensioner system. S&S Gear Drive Camshaft kits improve valve timing accuracy by eliminating timing chain lash as well as variations caused by the loose fitting stock cam drive sprockets. All stock chain drive components are replaced with S&S Gear Drive Cams and outer drive gears. This simple, effective solution reduces power loss by eliminating chain drag and allows more aggressive cam profiles and increased valve spring force to be used. Notes: Pinion shaft runout must be checked before installing S&S Gear Drive Cams. A hydraulic press and other professional tools are required to install S&S Gear Drive Cams. Additionally, material must be removed from the inner surface of the stock gear cover. The stock crankcase will require clearance for S&S .625", .640", and .675" lift cams. S&S recommends that gear drive cams be installed by a professional mechanic. Due to the inherent 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. We have found that with 160 pounds of valve seat force, the S&S 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. S&S 640G Cam Grind Complete Kit Valve Timing Intake: 25°-60° Valve Timing Exhaust: 65°-25° Valve Duration Intake: 265° Valve Duration Exhaust: 270° Valve Lift: .640" Centerline Intake: 107.5° Centerline Exhaust: 110.0° Lift @ TDC Intake: .228" Lift @ TDC Exhaust: .214" Fits Big Twin 1999-2006 (except Dyna 2006) Not legal for sale or use in California, or on any pollution controlled vehicles By: S&S CYCLE INC®