S&S MR103C chain drive camshaft kit for 1999-'06 HD® Big Twins except '06 HD® Dyna® are recommended for modi fed engines with larger displacement and higher compression. More torque and horsepower than bolt in cams can deliver. Stock valve springs in 2005–’06 engines may be used with MR103 and HP103 cams. An S&S oil pump and cam support plate, along with a stock 2007 and later style hydraulic cam chain tensioner upgrade is highly recommended for chain drive cams. Performance intake and exhaust is recommended for maximum performance increase.
All of these cams require high lift valve springs when used in 1999–’04 engines.
Not legal for sale or use on CA or EPA pollution controlled motorcycles."