Actually, shorting them is not what hurts. OPENS is what hurts, so you take an inCREDIBLY hot "oversmogged" engine, and I'm guessing those still ran 7mm wires, all you need is for one to start burning open inside, and you have a "lightning bolt" looking for a place to reflect back -- right into the ignition module.
Guys DO NOT EVER run an electronic ignition with one or more plugs/ wires unhooked. unless you ground them.
