with the distributor 'rocking' it may be losing good grounding at higher RPM, I'd find a washer to stop the movement [brass preferably], and maybe add a ground wire from the case to the block
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics
