I've also used my lathe as a drive unit to test alternators, generators, distributors, etc. Unless the power company runs out of juice, the battery never runs down! If you really want to stress the coil, open up the plug gap to about .050"- - - - -That requires 20KV or so to fire the plug.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!