In 1973, Pettyjohn debuted at Dover, qualifying 29th. It didn't begin well for Pettyjohn, as a crash left him in last place-40th on the field. Luckily, Pettyjohn was able to atone for that when he returned to Dover in the fall. He started the race in 14th and slowly made his way up to tenth place-his only career top-10, despite being twenty-one laps down.
Pettyjohn was involved in both Dover races in 1974 for Donlavey's team, with mediocre results. He did earn a career best start of 13th in both races, while Pettyjohn finished 32nd and 24th. In the fall race, Pettyjohn led his first career lap, but that was his final career race.