...eye catching addition to a perfect engine compartment... Every time I see/hear "nailhead," I tell myself I need to find out when description evolved from original "nail-valve" to "nailhead." Growing up with Buicks and religiously reading everything about them in then premier gearhead magazine, Hot Rod, my "education" included original phrase. Only evidence I have left is from an April '66 article on "Blueprinting Buicks." Still can't quite get used to "nailhead"...