S&S MR103C chain drive camshaft set for 2006 HD Dyna® and 2007-2016 HD big twins are recommended for modifed engines with larger displacement and higher compression. More torque and horsepower than bolt in cams can deliver. Stock valve springs in 2005-2006 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.