When a cylinder head is disassembled, the stem height on one of the valves is found to be too high. Which of the following can correct this?

To correct the issue of a valve stem height being too high, one effective method is to install a new valve seat. When the valve stem height exceeds specification, it can make it difficult to achieve proper valve closure and can lead to adverse effects on engine performance, including improper sealing and increased wear.

Installing a new valve seat can help to lower the valve’s effective height by providing a fresh surface that aligns properly with the valve and its seating position. This method can ensure that the valve operates within its intended parameters, allowing for optimal clearance and function within the cylinder head.

The other methods, while they may address different issues associated with valve operation or seating, do not directly resolve the specific problem of an excessively high valve stem height as effectively as installing a new valve seat. For example, regrinding the valve or valve seat might help in other scenarios but does not inherently lower the height of the valve stem. Using a shim can reestablish the proper clearance, but it does not address the root source of the height discrepancy itself. Thus, installing a new valve seat is the most appropriate corrective action in this case.