When grinding a valve to adjust clearance, the end of the valve stem should be ground to which shape?

When grinding a valve to adjust clearance, the end of the valve stem should be ground to a square shape. This flat end ensures that the valve properly seats against the valve seat when closed, providing an effective seal and preventing leaks. A square shape allows for a more uniform contact surface, which is crucial for even wear and reliable operation over time.

The square shape also facilitates better alignment within the valve guide, reducing the chances of binding or excessive wear. Properly shaped valve stems contribute to optimal engine performance, as they ensure the valve opens and closes accurately to match the timing requirements of the engine.

Other shapes, such as concave or convex, would create uneven contact points and increase the risk of leakage and quick wear, while a point would result in minimal contact area and poor sealing. Thus, grinding the valve stem to a square shape is essential for maintaining the overall efficiency and longevity of the engine.