Valve guide clearance

Higher end shops hone the guides to the finish size instead of reaming. A reamer doesn't put the necessary crosshatch in the guide for oil retention, otherwise, oil would just shoot on past and into the ports. Just think if you bored your cylinders with a boring bar and didn't hone them to put a crosshatch in them. Reaming is faster and they make more profit, but you don't get a quality job.