Here is why your car's timing belt is essential: Each cylinder in your car's engine has an intake and exhaust valve at the top and a piston at the bottom. The valves are attached to a camshaft. The pistons are attached to a crankshaft. The valves and pistons all need to move in sync within the cylinder, which means the camshaft and crankshaft need to turn in sync. The timing belt keeps your camshaft and crankshaft turning in sync and keeps your car running.