When grinding a new set of cylinder valve seats, which of the following should be performed before the machining?

Before machining a new set of cylinder valve seats, it is essential to install the valve guides first. Valve guides are critical components that ensure the proper alignment and stability of the valves within the cylinder head. Proper installation of the guides is crucial because they determine the positioning of the valve stems and thus have a direct impact on the machining process of the valve seats.

If the valve guides are not installed before grinding the valve seats, the seats may be machined at the wrong angle or depth relative to the valve stems, leading to improper sealing and poor engine performance. Once the guides are in place, the valve seats can be accurately machined to ensure optimal sealing and valve operation.

Other actions such as installing the valves or rockers or adjusting the valve yokes should occur after the machining process, as they are dependent on the precise dimensions set by the already installed valve guides and machined seats.