Why It’s Important and How to Tell Which One Your Car Has Timing belts and timing chains do the same thing: They connect the engine’s crankshaft to the camshaft, which opens up the valves of the engine. The valves let fuel and air into the engine, and exhaust out. However, timing chains and timing belts are made of different materials (metal and rubber, respectively), installed in different ways, and have different maintenance costs (the most important characteristic for car owners). We’ll explore what these car parts do, how they differ, and how much they cost. What Do Timing Belts and Timing Chains Do?