I am building a 450-500 hp honda civic with a d16y8 head, i purchased brand new valves , and i was wondering how do I get these valves to seat and seal the chamber for combustion? Is lapping the valves effective enough to ensure the head will hold compression or do I have to go the extra mile and get some precision machine work done??
Since it is high performance, I would let a reputable automotive machine shop do a 3 angle valve job. Better flow and performance and everything gets checked, including checking for cracks in the aluminum head. Have it surfaced for a good head gasket seal also.
Find a machine shop that has experience in performance work.