- The replacement of an engine’s Timing Belts is a mechanical service of moderate complexity performed by experienced Technicians. The Timing Belt coordinates the “timing” of each crankshaft revolution to each camshaft revolution. The camshafts function is to open and close the engine’s air intake and exhaust valves thereby impacting the “smoothness” with which the vehicle idles and operates. When the timing belt breaks, the engine stops. When it is stretched, the valve openings and closings are timed improperly causing the aforementioned performance issues.