Lorenzen made his NASCAR debut in 1956 at Langhorne Speedway, finishing 26th after suffering a broken fuel pump and earning $25 in prize money. He subsequently moved to USAC stock car competition, winning the 1958 and 1959 USAC championships driving a Chevrolet prepared by the Talarico brothers. His USAC success caught the attention of Holman Moody, one of NASCAR's most prominent teams, and on Christmas Eve 1960, team owner Ralph Moody called Lorenzen with a contract offer that would transform his career.
Lorenzen joined Holman Moody for the 1961 season and immediately began winning: the Grand National 200 at Martinsville, the Rebel 300 at Darlington, and the Festival 250 at Atlanta in his first year alone. Between 1961 and 1966, he built one of the most commanding records of NASCAR's golden era, beating the top drivers of the period on the sport's most prestigious circuits.
In 1963, Lorenzen became the first NASCAR driver to earn more than $100,000 in a single season, with total winnings of $122,000. That year he won six races including the Atlanta 500, the World 600 at Charlotte, and the Volunteer 500 among others. His 1964 campaign added eight victories at tracks that remain fixtures on the modern NASCAR Cup calendar: Bristol, Atlanta, North Wilkesboro, Martinsville, Darlington, and Charlotte. In 1965 he won the Daytona 500, the Virginia 500, the World 600, and the National 400.
One of the most discussed race cars in Grand National history appeared at a 1966 Atlanta race when Lorenzen drove a car owned by Junior Johnson. The Ford featured a sharply sloped front end, a lowered roofline, narrowed side windows, a lowered windshield, and a raised tail section in an unconventional aerodynamic configuration. Rival drivers nicknamed it "The Yellow Banana," "Junior's Joke," and "The Magnafluxed Monster." NASCAR, seeking to boost attendance that had suffered during Ford's partial boycott of the series, allowed the manifestly non-standard car to compete; Lorenzen crashed while leading the Dixie 500 on lap 139. The car ran in only that one race.
Lorenzen retired in 1967 but returned in 1970, driving a Dodge Daytona in the World 600 and dropping out while leading on lap 252 of 400 with engine failure. He made additional appearances in 1971 and 1972, the latter ending at the Old Dominion 500 at Martinsville Speedway. A practice crash while attempting to drive for the Wood Brothers ahead of the 1971 Southern 500 resulted in serious injuries that effectively ended his realistic prospects as a full-time competitor.
Racing for money rather than championship points, Lorenzen never mounted a sustained campaign for the annual Grand National title, yet his 26 victories on superspeedways and major events made him one of the defining faces of the sport during the 1960s.
Lorenzen died on December 18, 2024, from complications of dementia at the age of 89. He was named one of NASCAR's 50 Greatest Drivers in 1998 and one of NASCAR's 75 Greatest Drivers in 2023. He was inducted into the Motorsports Hall of Fame of America in 2001 and the NASCAR Hall of Fame in January 2015. Lorenzen once said of the death of Fireball Roberts: "When NASCAR lost Fireball Roberts it was like Santa Claus doesn't exist at Christmas and it just took everything out of the race" — a reflection that captures the fraternal intensity of the era in which he competed.