The overhead camshaft is also something that we think of as a relatively new development, but it's not. In 1898 the Wilkinson Motor Car Company introduced the same feature on a car. Usually this type of engine has the camshaft mounted in the cylinder block, and the valves are opened and closed by push rods. Timing Timing refers to the delivery of the ignition spark, or the opening and closing of the engine valves, depending on the piston's position, for the power stroke. The timing chain is driven by a sprocket on the crankshaft and also drives the camshaft sprocket.
Engines run on a vacuum system.
A vacuum exists in an area where the pressure is lower than the atmosphere outside of it. Reducing the pressure inside of something causes suction. For example, when you drink soda through a straw, the atmospheric pressure in the air pushes down on your soda and pushes it up into your mouth. The same principal applies to your engine. When the piston travels down in the cylinder it lowers the atmospheric pressure in the cylinder and forms a vacuum.