Isaac grew up on a farm near Catawba, North Carolina, the second-youngest of nine children. He finished school after the sixth grade, which led to the incorrect rumor that he could neither read nor write.
NASCAR career
He began racing full-time in 1956, but it took him seven years to break into the Grand National division. Isaac won the championship in 1970 driving the No. 71 Dodge Charger Daytona sponsored by K&K Insurance. His crew chief was Harry Hyde. Isaac and Hyde took the car to Talladega in November and set a closed-course speed record. Isaac won 37 races in NASCAR's top series during his career, including 11 in his championship season, and started from the pole position 49 times. Isaac currently holds the NASCAR record for most poles in a single season, with 20 in 1969. In 1970 he turned a 201.104 mph lap at Talladega, a record that stood until 1983. Isaac dropped out of the 1973 Talledega 500 mid-race in an impulsive decision which surprised his pit crew and the team owner. "I wasn't afraid I was going to wreck...I don't have anything to prove to myself or to anybody else. I know how it feels to win and lose. I know how it feels to be a champion. And now I know how it feels to quit. It just entered my mind at that moment," Isaac said. "I decided to quit and that was that. Bud Moore didn't know I had quit until after the race. I didn't know about Smith at that time." . Isaac did not participate in any further 1973 NASCAR Winston Cup races after Talladega, and the presumption by sports commentators in late 1973 was that he was retiring from the sport. Ultimately, Isaac did return to NASCAR racing as a driver from 1974 through 1976, on a reduced schedule.
Isaac also made his mark outside of NASCAR. In September 1971, he went to the Bonneville Salt Flats in Utah and set 28 world speed records, some of which still stand.
On Saturday night, August 13, 1977, while running fourth, Isaac pulled out of the Winston 200 late model sportsman race at Hickory Motor Speedway with 40 laps left, and called for a relief driver, collapsing on pit road of heat exhaustion. Weather reports for the area that day showed temperatures which had reached at mid-afternoon, and were still around at the time of Isaac's collapse. Though Isaac was revived briefly at the hospital and was conversing with friends, he later died from a heart attack caused by heat exhaustion, at 12:45 a.m., August 14, 1977, 13 days after his 45th birthday. Details of Isaac's pit lane collapse on the night of his death were given to reporters by friend and former racing driver Ned Jarrett. Jarrett asserted at that time that the reason Isaac left the 1973 Talladega 500 was because he "had heard a voice that told him to quit".
