Definition - What does Timing Gear mean?
Timing Gear is a component of an internal combustion engine which is connected by a chain, gears, or a belt to the crankshaft on one end and the camshaft on the other. It is marked with tiny increments all around its perimeter which correspond to degrees of timing from the straight-up timing position of the camshaft and crankshaft. These marks assist the individual who is tuning up the engine to set the timing to the determined optimal timing degrees of the camshaft and engine designers.
Petropedia explains Timing Gear
In order to set an engine's timing gear to the correct inclination, the mechanic must confer with the engine manufacturer as well as the camshaft manufacturer. The purpose of timing an engine with the gear is to ensure that the valves open and close at the correct time to best fill the cylinder with an air/fuel mixture as well as to release all fumes from the exhaust cycle of the cylinder. A mere few degrees off can be the difference between an engine that performs perfectly and one that will not run correctly. A poor running engine will make less power and use more fuel than a properly-timed engine. In the perfect relationship of timing, the timing gear can be set so that the intake valve will begin to open as the piston is still moving downward in the cylinder walls and sucking the fuel into the cylinder. This would aid in getting as much fuel as possible into the combustion chamber. Also, the exhaust valve would remain open as long as the piston is moving upward in the cylinder and pushing the exhaust fumes out of the combustion chamber so that there is no contamination to the incoming fuel mixture.