Which method is NOT used to correct excessive valve stem-to-guide clearance?

Reaming for oversize is not typically a method used to correct excessive valve stem-to-guide clearance. Instead, this process is primarily utilized to enlarge a valve guide to accept a larger (oversize) valve stem when the original valve guide has been worn and needs to accommodate a new valve stem size.

In contrast, knurling the valve stem or guide, and replacing the guide altogether, are established methods used to address excessive clearance. Knurling involves creating a textured pattern on the valve stem or the inner surface of the guide to increase contact area and thus help retain better tolerance. Replacing the guide is a more direct and effective approach when wear exceeds acceptable limits, ensuring the proper fit and function of the valve train.