If a valve has a 45-degree face, what degree would the seat typically be?

In the context of valve and seat design in small engines, when a valve has a 45-degree face, the seat is typically cut at a slightly different angle to ensure a proper seal. A 46-degree seat is common because it allows for better contact and sealing between the valve and the seat. The slight difference in angle facilitates the optimal closure of the valve against the seat, which is critical for maintaining compression and preventing leaks in the combustion chamber.

The angle chosen for the seat must account for wear and the geometry of how the valve closes. If both the valve and the seat were exactly 45 degrees, they may not align perfectly when subjected to stress and wear during operation, which could lead to sealing issues over time. Thus, the 46-degree seat provides that essential compromise for effective sealing and durability in the engine's operation.