In 1967, GM sold the design to Kaiser-Jeep. The muscle car era had taken hold, and GM no longer felt the need to produce a V6, considered an unusual engine configuration in North America at the time. The energy crisis a decade later prompted the company to buy the design back from American Motors (AMC), who had by that point bought Kaiser-Jeep, and the descendants of the early 231 continue to be the most-common GM V6 as it developed into a very durable and reliable design.