Ground wire shakes under voltage.
 

Check this out. I've been having a lot of electrical gremlins lately so Ive gone overboard on the mods. If it's suggested I do it. I made a ground wire out of # 10 wire the goes from the end of the neg cable to the firewall(coils) then to the rotor housings. When I crank the starter the wire shakes sideways 3/8 to 1/2 inch???