My ever-deteriorating memory tell me the term "nailhead" came as a result of the head design of the earliest Buick V8 engines.

These engines, with their narrow vertical valve covers, just gotta be the handsomest engines ever made, but the valve size was pretty limited by the design of the heads. The small valves look like nails, hence the nickname "nailhead". In fact we used to hear them referred to as "nail-valve engines" sometimes.

I wish I had one. I don't need one, but that doesn't matter. I wish I had one anyway.

Jim