Hi-Riders (1978)

A couple scam a Hi-Rider out of some cash during a drag race, and when he refuses to pay, they track him down to the gang's hideout. Lucky for them the leader is a good, reasonable guy, and the couple start hanging out with the gang. However, after a fatal collision of the son of the "big man in town" during a race, the gang has to fight for their lives against the man's legion of hillbillies.