A lap by lap description of two automobile races, the Indianapolis 500 and the Riverside Grand Prix, make up three fourths of this story. The other quarter is devoted to a detailed and highly technical explanation of the designing, building, and testing of a car to be raced in the Indianapolis classic. The story centers on Woody Hartford, a road race driver and his Black Tiger, Worm MacNess, his friend and mechanic, and their rival, Pete Elsworth, an Indianapolis winner. A long-standing feud between road race and indianapolis drivers culminates in Woody taking his Black Tiger to Indianapolis and outdriving Pete in a thrilling race. The characters take a back seat to the ears in this book. For the high school boy who loves ears and is conversant with the technical language of automobiles.