denny,

have never experienced vapor lock here in the lovely southwest, but my 216 does tend to want to run a little "funny" when it gets hotter. actually what i notice the most is after repeated stops in 100 plus, i actually have to choke it a bit when starting and upon initial driving in order for it to run decent. have always wanted to investigate this condition more but since it hasn't stranded me just yet, it has not been a priority.

i haven't checked compression or valve clearance or had any major part of the original engine apart at all (unlike the work you've done) so i have no idea if that would cause this problem, but it seems like yours should be running like a top.

will be curious to see what you find out.