Lapped valves by hand for 12 years, then a guy in Wichita showed me a $40 tool that does it better
I always figured hand lapping was the only way to get a real seat, but he ran a pneumatic lapper on a Lycoming jug and the contact pattern was cleaner than anything I've done with a stick. Anybody else switched over, or am I gonna regret trusting a tool over my own hands?