Reventlow's parents' marriage, Hutton's second of seven, was tumultuous and did not last; after the couple divorced in 1938, Reventlow became the subject of a bitter custody battle. In 1944, Reventlow's father was awarded custody until he reached school age, after which his mother would gain custody. Before his father was to relinquish custody, he sent Reventlow to Canada. Hutton regained custody of Reventlow in 1945. Reventlow was largely estranged from his father until the Count's death in 1969.
In 1948, at age 12, Reventlow was introduced to the world of Grand Prix motor racing when his mother married Prince Igor Troubetzkoy, who won the Targa Florio that year. In his teenage years, Reventlow's money afforded him the latest in exotic cars, which led to his involvement in motor racing.
Reventlow began his racing career in America in the mid-1950s, initially with a Mercedes before moving to an 1100cc Cooper in 1956. The next year he went to Europe to buy a Maserati, which he crashed heavily at Snetterton, escaping unhurt. He also briefly drove a Cooper Formula 2 car, before returning to the United States. He then set up his own company in Venice, California, to construct Chevrolet-powered race cars he named Scarab with Phil Remington as chief Engineer. Along with hired driver Chuck Daigh, the two were initially successful in racing. They won the majority of major sportscar events they entered, often in competition with the Cunningham team of Lister Jaguars. Reventlow had looked at buying a Lister Jaguar, but thought that he could build a better car. Daigh drove a Scarab to victory in the 1958 Riverside International Grand Prix in California, beating a field of international race car teams, including the world-famous race car driver Phil Hill and the Ferrari Team. Carroll Shelby drove a Scarab to first place at Continental Divide Raceways in Castle Rock in Douglas County, Colorado, where he broke a course record.
In Hollywood, Reventlow became friends with fellow auto enthusiast James Dean and competed in club events around California. On September 30, 1955, he was one of the last people to speak to Dean when they met on their way to an auto race in Salinas, California. Reventlow said he had coffee with Dean at a restaurant approximately thirty minutes before Dean was killed in an automobile accident while driving his Porsche 550 Spyder in Cholame, California.
On March 24, 1960, Reventlow married Actress Jill St. John in San Francisco. They separated in October 1962. St. John filed for divorce on October 2, 1963, citing extreme cruelty; she stated that Reventlow called her "stupid and incompetent" in front of others and bullied her into taking part in dangerous Sports. Their divorce was granted on October 30, 1963.
His racing team was much talked about for having built the first Formula One race car in America. Shifting operations overseas to Britain, Reventlow's team had little success racing the Scarab cars in Formula One against the new rear-engine race cars. He went back to the drawing board and built a competitive prototype Scarab rear-engined car, but had become less interested in racing before its testing was complete. In 1962, he shut down the operation, leased the California facilities to Shelby, and quit auto racing altogether.
On November 6, 1964, Reventlow married ex-Mouseketeer Cheryl Holdridge in a lavish ceremony in Hollywood before 600 guests. Reventlow's mother, Barbara Hutton, could not attend the wedding because of illness but gifted the couple with a $500,000, five-bedroom home set on 21 acres in Benedict Canyon.
Reventlow's organization constructed a total of eight Scarabs during its existence. In a 1971 interview, Reventlow confirmed that three front-engined Chevy-powered Sports cars, three front-engined formula cars, one rear-engined formula car and one rear-engined Sports car were built. Two of the front-engined formula cars were powered by Reventlow-commissioned engines drawn up by American racing engine designer Leo Goossen to Reventlow's specifications, while the third car was powered by a Goossen-designed and engineered Offenhauser engine. The rear-engined formula was powered by a modified Buick powerplant; this engine and the suspension/brake package were taken from this car and used on the rear-engined Sports car, the last Scarab built.
In 1972, Reventlow was seeking real-estate developers as partners to build a ski resort in Aspen, Colorado, where he had a home. He was an experienced pilot, with thousands of hours, rated fully for IFR on multi-engine planes, but on July 24, 1972 Reventlow was a Passenger, scouting locations for real estate in a Cessna 206. The pilot was an inexperienced 27-year-old student who flew into a blind canyon and stalled the aircraft while trying to turn around. The plane plunged to the ground, killing all aboard.
