Exhaust valve

a small piece filled with a lot of technology

Exhaust valves are not made of ordinary steel, but of austenitic hi-tech steel alloys containing chrome, manganese and nickel.

Exhaust valves often require to be built out of two different materials, one for the stem for optimal heat transfer and for tempering the top of the stem, the other one for the head for optimal heat resistance.

If needed, the seat of the exhaust valve can be reinforced with stellite in order to further improve their heat resistance.

For high performance engines, even that is not enough. In such cases, nickel-based super alloys or even titanium are used, often in conjunction with hollow stems filled with sodium, which helps to speed up the heat transfer from the seat to the valvetrain, thus reducing the valve temperature by as much as 100 degC.