Would you? Or would you expect AMC to have done that already? As luck would have it I've found the grinding paste but the stick with the rubber ends has gone walkabout. In the past I have clamped the valve into a drill chuck and pulled gently while spinning the drill - I suppose that's probably not the correct way?
You shouldn't have to and TBH I don't think it achieves much but I did find a slightly ripply cut seat once that I did my best to grind flat.
If you are worried, pour some liquid (meths, petrol etc )onto the valves with the head upside down and see if anything significant leaks through with the valves held in by the springs and retainers.
Thanks. I did that when measuring the head volume, although with water. I did fetch a valve out to make sure everything looked clean and swarf-free. I'll be doing them all and dousing with carb cleaner before re-oiling and assembling
I always lap valves and have used an oscillating attachment in a drill for years but if you’re only doing eight valves a stick and suckers is better than just a drill.
I personally wouldn't bother, its a brand new valve on a brand new seat. Brand new car engines of the production line don't get the valves lapped. As above you could check them all for leaks with meths or petrol, or if you have a vacuum pump and gauge apply that to each port (inlet and Exhaust) and apply vacuum as they do when you get heads reconditioned Thats my view on it, and I didnt bother with my new AMC heads and they all held vacuum fine
