What is the recommended procedure when machining a cylinder head's integral seats and valves?

The recommended procedure when machining a cylinder head's integral seats and valves is to machine and then lightly lap. This approach is effective because machining the integral seats ensures that they are perfectly flat, clean, and at the correct angle. It creates a smooth surface that enhances the sealing capability when the valve closes.

After machining, lightly lapping the valves further refines the seating surface by removing any minor imperfections that may still exist after the machining process. This step helps to achieve a better fit between the valve and the seat, which is crucial for optimal sealing and efficient engine performance. The slight abrasion from lapping also allows for a better surface finish, leading to improved longevity and reliability of the valve-seat interface.

The other methods mentioned, such as machining without lapping or solely relying on lapping, do not provide the same level of precision and effectiveness in creating a good seal. In particular, not machining first means that any imperfections in the seat may remain, leading to potential leaks. Therefore, the combination of machining and then lightly lapping ensures the best results for performance and durability.