Jenkins attended Cornell University where he studied mechanical engineering, and he used his training and skills to build engines. He was inducted into the International Motorsports Hall of Fame in 2008 for his engine building expertise in the National Hot Rod Association (NHRA) Pro Stock division. His innovations included drag racing’s first kickout oil pans, Pro Stock strut-style front suspension, dry sump oiling system, cool cans, electric water pump fan, gas port pistons and slick-shift manual transmissions.

Considered the "Father of Pro Stock", Jenkins-built engines were used to win five NHRA Pro Stock championships and three American Hot Rod Association (AHRA) championships. In 2001, he was voted No. 8 among NHRA Drag Racing’s greatest racers in a poll. He won only 13 NHRA national events but earned his spot in drag racing’s top 10 because of his contributions to the advancement of normally aspirated engines for drag racing.

Jenkins briefly shed his gruff exterior in 2001 after making NHRA’s Top 10 to say: "Having so many of the people I’ve worked with show up at my [70th birthday] party in January meant a lot to me. I’ve always had a lot of personal satisfaction from the mechanical end of the sport."

Legend has it that Jenkins was nicknamed "Grumpy" for having a no-nonsense attitude at races. According to the Motorsports Hall of Fame of America, Jenkins’ continual search for improved performance left little time for idle chatter with his racing colleagues.

Jenkins continued to build engines in Pro Stock through the mid-2000s. He was involved in several Pro Stock teams in the modern era including Cagnazzi Racing, Jim Yates Racing and Dave Northrop.