It's difficult to rate this movie, as it's such a product of its times and the film was NOT intended to be wached in 2021 by a 57 year-old guy! Instead, it was made for the drive-in movie crowd of the day...teens and young adults who wanted some silliness and rock 'n roll. And, because of this, it's not surprising that much of the film makes fun of adults...the 'squares' who are more like cartoon characters than real adults.
John Abernathy III (John Ashley) is a young man who leads a double-life. To his matronly aunts and the other adults in his life, he's a respectful and stuffy guy. But when they aren't around, he's into rock 'n roll and his jalopy. Despite the title, this hot rod isn't a major part of the film...it's John's music and his relationship with a new girl in town, Jody. Additionally, some jerk tries to destroy John by framing him for crimes and exposing his double life. Along for the ride is the ill-fated Gene Vincent...there to provide a few songs along with John's.
The film is modestly entertaining...and John Ashley went on to do some Beach Films for AIP....although like so many of these 'teen stars' he was a LOT older....24 when he made "Hot Rod Gang" and 31 when he appeared in "Beach Blanket Bingo".