Engine timing marks are indicators used to set the timing of an engine's ignition system. They are usually found on the crankshaft pulley or the flywheel.
Many engines have two or three marks on the inner crankshaft pulley to line up with the arrow mark on the engine block. The mark set to the block mark on the crankshaft is the same as the mark set to the head and the crankshaft when the chain or timing belt is installed properly. Depending on the type of engine, the top dead center mark can be left, center or right mark. The top dead center mark is the center of the three marks on most engines.