You can also get reamers at MSC Supply for much less than automotive reamers. They are intended for limited use: I get about 24 valve guides per reamer from these when reaming by hand (patience, patience...) before they lose their edge. After that they tend to ream on the small side, and take more time, so I chuck them in a [slow] drill, heat the guide with a torch and run it thru, then let it cool and run a fresh reamer thru. This lets my newer reamers last longer so I don't have to charge as much as some shops do, in the end. Those poor guys with the big reamers (Serdi, Sioux, etc.) can do a nice job quickly, but their reamers cost like $250 each, so they do have to charge more.
For a long time the APE valve guides came with holes almost to spec for the Honda valves. Most needed another 0.0005" ream if brand-new "Made in Japan" automotive valves were used (these are popular aftermarket valves for these engines). Last year, though, APE's guides began coming out 0.001" undersize, so I've been reaming a lot more lately. It sort of 'feels' like the 1970s again, when Honda's guides (cast iron, all) came 0.0004" undersize and you had to use their hand reamers for the final fit after installing them.
