A camshaft is simply a shaft on which cams are mounted. The camshaft is mounted in bearings in the lower part of the cylinder block in most inline engine. In few engines, it is located on the cylinder head. A cam is a device that changes rotary motion of the camshaft into linear motion of the follower or lifter. The cam has high spot or love the follower riding on the cams will move away from or toward the camshaft as the cam rotates. A camshaft is responsible for opening the valves. A camshaft has a number of cams along the length, two cams for each cylinder, one to operate the inlet valve and the other the exhaust valve. The camshaft is driven by the crankshaft either by a pair of meshing gears or by means of a pair of timing sprockets connected by a chain. The camshaft turns at half the speed of the crankshaft. The gear and sprocket maintain a definite time relationship between the camshaft and the crankshaft to ensure opening the valves exactly at the correct time in relation to piston position.