What should be measured to evaluate valves for wear?

To evaluate valves for wear, it's important to consider multiple dimensions and characteristics that can indicate their condition. The correct choice includes measuring head diameter, valve length, stem diameter, and face/seat width.

Head diameter is crucial because it affects the sealing surface area of the valve against the seat. If the head is worn or unevenly shaped, it may not seal properly, resulting in loss of compression and engine performance.

Valve length is significant as it determines how well the valve can open and close. Any elongation due to wear can affect the timing and the efficiency of the engine's operation.

Stem diameter is essential for assessing the condition of the valve guide. A worn stem can slide too freely, creating gaps that allow oil to enter the combustion chamber and lead to performance issues.

Face/seat width is critical as well, since the amount of surface area that makes contact between the valve and the seat can determine how effectively the valve seals. Worn face or seat width can lead to leaks and decreased engine efficiency.

The inclusion of all these measures gives a comprehensive picture of the valve's functional integrity, enabling better assessments of potential wear and necessary repairs or replacements.