If they are pretty good they shouldn't move much. Maybe just enough to see that it moves. But I've seen some with quite a bit of play. Still seemed to run ok. Not much you can do really, unless you wanted to get bronze valve guides put in, which probably isn't worth it. The cylinders are probably pretty well worn too if the valve guides are beat. I/C engines have a bronze guide on the exhaust valve. The go kart/quarter midget guys get them pressed in to both when they build an engine.