I'll try and post that pic you asked for (PM) when I get home but any connection to metal on the engine will be a good ground. I only said the ear on the head because it's what I always used and usually convenient. The only reason you're not supposed to connect the ground to the battery is to prevent sparks from igniting fumes from the battery and causing it to blow up. It make quite a mess when that happens. BTW, always hook up the ground cable last.