I noticed both times iv had the head off the K321 that the plug (old and new) does not protrude into the combustion chamber. As in its too short. Is there a longer plug that works? I though about opening the hole in the combustion chamber but not sure I want to do that to a good original head. Otherwise I feel milling will be required on the outside in order to obtain a good sealing surface. I feel like if the plug was more exposed to the chamber I would have better efficiency and more power. Anyone looked into this?