Agated neighborhood in an upscale Tampa suburb is a strange place to send your carburetors for rebuilding. The shop sits in the three-car garage of a lovely home, alongside a similarly lovely turquoise 1957 Chevrolet Nomad wagon. There is a long table with some chairs, and a workbench is parked next to a couple of soda blasters. All is lit by florescent bulbs overhead. This the modest domain of Riley’s Rebuilds, a carburetor rebuilding service headed by Riley Schlick. Riley is a 17-year-old girl: A surfing, skating, soccer-playing, Jeep-driving high school senior. Four of her high school friends, all girls,...