Which measurement is important for evaluating valve seating?

The maximum width of the face and seat is crucial for evaluating valve seating because it directly impacts how well the valve seals against the seat within the cylinder head. Proper seating ensures that no compression escapes during the engine's operation and that the engine runs efficiently. A valve that has a correct and even width across its face provides a larger area for contact with the seat, reducing the chances of leaks and facilitating better sealing. Inadequate width can lead to uneven wear or improper sealing, which can negatively affect engine performance.

The angle of the valve face is also important, but its significance lies more in the alignment and the way it interfaces with the seat rather than the direct measurement of sealing effectiveness. The overall length of the valve primarily affects the distance it moves, while the diameter of the valve spring pertains to the compression and tension characteristics of the spring rather than seating quality. Therefore, while both the angle and overall dimensions are important in their own contexts, the maximum width of the face and seat is the most direct measurement affecting valve seating effectiveness.