little charger is right, its the depth of the pocket or depth of combustion chamber how ever you want to say it.
if you had a low compression head to start with you could be fine ?


you just need to measure the depth of the chamber on this now ?

I will also check out what my spare head is today as well, mine is the later version head part number omc 339221.
will be interesting to see how deep that is at the moment.