Following the 1968 season, Richard Petty announced he was leaving Chrysler and going to Ford for the 1969 NASCAR season. The money allocated for Petty was used to develop the Plymouth Indy engine.
Harry Weslake was commissioned to build a double overhead valve version of Plymouth's 318 V-8. Work started February 1969 and the first engine was delivered to Andy Granatelli's team in April of that year.
Although the engine lacked the horsepower necessary to compete at Indy and some of the other big tracks on the trail, it had plenty of bottom-end torque which made it quite competitive on the short oval tracks.