TULSA, Okla. – Every year, they come to Oklahoma for the muck. The fans in overalls and ball caps spangled in flames and Chevy logos. The kids with earplugs. The Hooters girls. The young drivers strutting in their jumpsuits and the graying vets craning over crankshafts. They all come to get dirty. For racing devotees, there's only one place to be in January during the motorsport world's off-season: Tulsa's Chili Bowl Midget Nationals – the biggest, most-eclectic dirt-track race in the country. Car owners plan their year around it. Drivers spurn their regular circuits for it. And the Oklahoma dirt...