The primary function of a timing chain and gears is to ensure the synchronization of the camshaft and crankshaft in an engine, controlling the timing of valve operation and the intake and exhaust processes within the cylinders. By maintaining precise synchronization, the timing belt enables the following functions:

1. Valve Timing Coordination: The opening and closing timing of the engine's valves is crucial for proper combustion and performance. The timing belt ensures that the camshaft and crankshaft rotate in perfect harmony, ensuring that the valves open and close at the correct times for optimal cylinder compression and combustion.
2. Prevention of Piston-Valve Interference: The pistons and valves in an engine must maintain a certain clearance to avoid interference. The precise synchronization provided by the timing belt ensures that the camshaft and crankshaft movements are always in the correct phase, preventing contact between the pistons and valves.
3. Smooth Engine Operation: The accurate synchronization of the timing belt eliminates vibrations and imbalances during engine operation, providing smooth power output and low noise levels.