lapping

I'm about halfway through my top-end rebuild, and I decided to lap my valves while they were out. I'm regretting that decision now. They weren't too bad, but there was a small amount of visible pitting and roughness. Now, I've got these grooved rings around the valve and seat, which is - if I...

Another greenhorn question, but when should one lap the valves? There's a lot of great information on this site about HOW to lap, but I have yet to see WHEN to lap the valves. I'm installing new Kibbelwhite valves, and I assume since they're new, the valves need to be lapped. Other than that...