Well , it's nice to here there's another 216 fan out there .
These gentle motors run just fine , even completely stock. Though some carb improvements can be beneficial.
Definately , the head should be treated to some hardened velve seats . The new valves you fit are already of a quality material.
Consider modifying the timing gear front cover attachment . At the bottom , the cover bolts are fitted thru the front main bearing cap . To remove the cover at any time , the sump has to come off ! .
I drilled the cover out , and tapped the front main cap , and screw the bolts in from the front .
Have fun , grin