What do the timing marks of an engine tell you about a car?

Timing marks on a car are used to indicate the pattern of cylinder head movement in the engine relative to the engine's timing belt. They are necessary to ensure that the timing belt is aligned properly with both the cylinders and crankshaft when the belt is replaced during maintenance.

Different engines have different timing patterns depending on the firing pattern used by their ignition system, the length of travel of their pistons and other engine design factors. Timing marks are critical to help ensure that a new timing belt is installed so that it correctly synchronizes the movements of the cylinder heads and crankshaft during the operation of the engine.