i know one thing for sure ..i run the same cam 722 lunati in my 67 camaro...and on alochol this weekend..i did a wheel stand peddled (2) x..still had a 1.32 60 ft...with a 5.98 et at 116 mph. at 3004 lbs....so i know your cam is a good one
.....
the breaking up and clearing up as you say it did round after round points to plugs...
i tell ya what Charles i ran a NKG #8 this past weekend and this was on Alcohol and did fine....so you could very well be too cold....
or you flushed some trash thru your carb or something simliar to that..needle seat sticking,,then free's up ..uhmmmmm i just wonder.
either way i think it will turn out to be an easy fix for you
IMO..
brian