Valves are devices or natural objects that regulate, direct or control the flow of fluids by opening, closing, or partially blocking various passageways. For example, valves open and close a cycle in an engine allowing the ingress of air and fuel into the cylinders.
- Engine valves contain two holes or ports in the upper enclosed end of the cylinder.s
- One port is the intake port. The other port is called the exhaust port. Air fuel mixture flows into the cylinder through the intake port. Burned gases leave the cylinder through the exhaust port.
- The two ports are open only part of the time. The rest of the time they are closed by the intake and exhaust valves.
- The valves are plugs with long stems that open and close the ports in the cylinder head. When a valve moves up into its ports, the valve seals tightly against a valve seat. In this position, the valve is closed, sealing the port
- When a valve is pushed down off its seat, the port is open. Then the air-fuel mixture or exhaust gas can pass through the port.