Motorsports rulebooks exist to, among other things, limit racecar builders' wild fantasies in the name of fairness in competition. But in probing the limits of those rules, sometimes carbuilders go too far. What's the most awesome banned race car ever?

Here's our pick. By the early 1950s, a generation of WWII-veteran gearheads had been using the aircraft-engine knowledge they'd learned in the service and applying it to hot rodding. Art Arfons and his half-brother Walt, who would go on to become masters of the land-speed-record realm, were racing an early version of their Green Monster race car powered by an Allison V12 from the Curtiss P-40. With several iterations of car, Arfons set the top speed at the NHRA National Championships for three years running, reaching amazing-for-the-time quarter-mile speeds in the 170s. He eventually reached 191 mph to beat "Big Daddy" Don Garlits, but by then, the NHRA had banned aircraft powerplants from competition. (One of the Green Monster cars was restored recently.)

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