Cliff Sealock paired up with car owner Harry Griffen in 1954 and won the Franklin Speedway championship that year. In 1955, he jumped into the seat of a car owned by John Davisson and won three more Franklin titles in a row. With Mighty Mouse painted on the side of the car, Davisson and Sealock ensured that the cartoon character would have special meaning for every auto racing fan in the state of Nebraska for years to come.
In 1960, driving for Jim Gessford, he won three track championships: Lincoln, Beatrice and David City. Sealock was also an excellent go-kart racer, and won the 1961 Central States Championship at Fremont.
After moving to California in the mid-1960s, Sealock enjoyed success racing sprint cars, setting track records and winning with both NARC and the California Racing Association (CRA), through the 1970s. Cliff drove the #4x sprinter of Speedy Bill Smith on several occasions when traveling back to his home state of Nebraska in the 1970s.