...BTW your Bieber avatar is awesome.-Malone
Yes the valves are recessed into the head but if the head is cut, the valves are recessed less while the piston protrusion remain the same. Something has to change to compensate. Thicker head gasket? or cut piston? cut valves to seat deeper?
http://www.vwdiesel.net/forum/index.php?topic=15782.0That's the porting article in question.
the really proper way is to cut valve seats and precup cups to the proper depth