The valve opens and closes at extremely high speeds under poor lubrication conditions and reciprocates at high speed in the valve guide.
The valve material and structure are also carefully designed. The intake valve is generally made of medium carbon alloy steel, such as chrome steel, chrome-molybdenum steel and nickel-chrome steel, while the exhaust valve is made of heat-resistant alloy steel, such as silicon-chrome steel, silicon-chrome-molybdenum steel, silicon-chrome-manganese steel, etc. The valve consists of a head and a stem, of which the head is used for sealing and usually adopts a 45° cone design.