timing gear
n (Automotive Engineering) (in an internal-combustion engine) the drive between the crankshaft and the camshaft, usually giving a ratio of 2 : 1
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014