What's a ';Nail-Head'; V8?

It's in the description of a '57 Buick....what is that?What's a ';Nail-Head'; V8?
Nailhead refers to an older generation Buick V-8. The valve covers sit upright on the motor and the valve stems point straight up, looking like nails in a board when the rocker arms are removed. Most V-8 motors the heads and valves are angled. Nailheads are very distinctive and sought after by hot rodders due to their unique look. The are also quite powerful.What's a ';Nail-Head'; V8?
It is a Buick V8 with heads that are more upright than other V8's making the engine narrower. This leaves less room for big valves so smaller valves had to be used hence the name Nail Head after the small valve head that looked like a box nail.