They can and they will. I had a poor ground on my 66 Dart. It boiled the battery in a short order, blew out light bulbs and made a mess of the paint on the drivers side of the engine and under the hood. I sent my valve covers off to Leanna and she had to blast the drivers cover 2 or 3 times to get the powdercoat to stick. :BangHead::BangHead: