There are usually four valves for each cylinder, two inlet valves and two exhaust valves. The inlet valves open to allow the air-fuel mixture into the cylinder, while the exhaust valves open to allow the exhaust gases to escape. The valves are opened and closed by the camshaft, which is driven by the crankshaft.
The camshaft has a series of lobes, or raised sections, which push on the valve stems to open the valves. The shape of the lobes determines how long the valves are open for, and when they open and close.
Valves are made of a variety of materials, including steel, titanium and aluminium. They are usually coated with a material such as chromium or nickel to prevent them from wearing out.
Valves are an important part of an engine and they need to be properly maintained in order for the engine to run efficiently. If the valves are not properly seated, or if they are damaged, they can cause the engine to lose power or even run rough.
