Which of the following is NOT a method to correct excessive valve stem-to-guide clearance?

Knurling the valve stem is not typically considered a method to correct excessive valve stem-to-guide clearance. This is because knurling, which involves creating a textured pattern on the valve stem to increase its diameter, may provide a temporary fix by adding material to the stem; however, it does not effectively address the fundamental issue of excess clearance in the valve guide.

Effective solutions for excessive clearance include knurling the guide, reaming for an oversize stem, or replacing the guide altogether. Knurling the guide can help regain a snug fit by increasing the diameter of the guide. Reaming for an oversize involves enlarging the guide's bore to accommodate a larger stem diameter. Finally, replacing the guide offers a permanent solution if the existing guide is worn beyond acceptable limits. Each of these methods directly addresses the issue of clearance, making them suitable choices, unlike knurling the stem.