The Nailheads are the older Buick V-8's. The 364, 400, 401, and 425 are all Nailheads and were phased out for the 350/455 which are not Nailheads. The term Nailhead came from how the valves looked like Nails since the stems were so long and the valve heads were so small.
If anyone has a pic of #13, it would be greatly appreciated! Nice write up Sent from my iPhone using Tapatalk