A valve with a sunken head due to high temperature is known as a:

A valve with a sunken head resulting from exposure to high temperatures is referred to as a dished valve. This term specifically describes the shape that the valve takes on due to the material deforming under extreme heat, leading to a concave or "dished" appearance.

In engines, the performance of valves is critical, and if a valve becomes dished, it may not seal properly, which can result in reduced engine efficiency, potential misfires, or even severe engine damage. The term effectively communicates not just the shape but also the possible implications for the engine's performance and integrity. Understanding this concept is crucial for diagnosing engine issues and maintaining proper function.