Car and light truck mechanic
When the fuel ignites in the cylinders, it forces the pistons down. Pistons are connected to the crank shaft by connecting rods. As pistons are forced down it causes the crankshaft to rotate. Cam shaft is connected by a belt, a chain, or gears to the crankshaft. As crank shaft turn it turns the cam shaft. The cam shaft has lobes which push valves open allowing air into the cylinders and exhaust out of the cylinders.