After lapping the valve seat, where should the pattern ideally appear?

The ideal pattern after lapping the valve seat should appear in the middle of the valve face. This positioning ensures that the valve makes proper contact with the seat during operation, which is crucial for maintaining a good seal. A pattern in the center indicates that the lapping process has effectively removed imperfections and created a uniform seating surface.

When the pattern is in the middle, it means that the valve is correctly aligned, allowing for optimal sealing and performance. A well-centered contact point reduces the risk of leaks when the valve is closed and helps maintain efficient engine operation.

A pattern appearing on the bottom or top of the valve face indicates misalignment or uneven wear, which could lead to issues such as poor sealing, increased wear, and potential overheating. Similarly, having only 50 percent of the pattern on the valve face suggests inadequate contact, which is not acceptable. Therefore, achieving a pattern in the middle is essential for proper valve operation.