Dobie has eyes for the cute new girl in school, Charlotte Lamarr, and gets a hot rod to impress her. He has competition from the rich and snooty Chatsworth Osborne Jr., so Zelda gives him a hand in thwarting Chatsworth's plans.
While Dobie and Maynard crash on their tandem bicycle, they meet Charlotte Lamarr, a girl crazy about speed. Despite Dobie trying to play up how fast they were going when they crashed, their cycling adventure can't compete with Chatsworth's sport car for speed. The only way Dobie can compete with Chatsworth for Charlotte's affections is to get a hot rod of his own. The first step is to get the $25 membership fee to join the Downshifters, a group of hot rod enthusiasts working under the supervision of an adult, Mr. Sullivan. The second step is to learn how to build a hot rod of his own with Maynard's help using whatever spare parts they can scrounge. The problems are the money, which he has to get from this father, and lacking the mechanical ingenuity, which they believe they know in the form of one, Zelda Gilroy. Convincing both Herbert and Zelda are no easy tasks. Even if they get this far, they have to beat Chatsworth in the upcoming sanctioned hot rod design and construction ... Written by