When HEI ignition was invented to comply with the 50,000 mile "service free" exhaust emission requirement of the Clean Air Act of 1968, there was a concern about the 50KV+ open circuit voltage capability of the coils they had to use being able to jump through the insulation of the 7MM wires commonly in use at the time. HEI wires on OEM systems became 8MM. The concern was somewhat misplaced, as a clean, properly gapped spark plug will fire at less than 10KV, regardless of what style of ignition system is used. There is NO WAY for firing voltage to rise higher than the voltage required to fire the plugs, so people who buy "flamethrower" coils and other P.T. Barnum Special ignition components like huge diameter wires are a prime example of his adage that "There's a sucker born every minute!" "A fool and his money are soon parted" has been true since the beginning of commerce centuries ago.
Jerry
