The cause was pneumonia, his daughter, Yvonne Mills, said.
An imposing driver who stood about 6 feet 2 inches and weighed as much as 240 pounds, Grant raced professionally from 1965 until 1978 against the likes of Mario Andretti, Lloyd Ruby and Parnelli Jones.
He was a multifaceted racer, competing in events using Indy cars, the open-wheeled cars seen in the Indianapolis 500; long-distance endurance races for sports cars; stock-car races; and Can/Am races, involving two-seated cars with high horsepower and very few restrictions.
Grant spent years driving for the racing great Dan Gurney on his All American Racers team and teamed with him in grueling endurance events.
"He was always a threat," Gurney said in an interview on Friday. "It didn't seem to matter what sort of car he was in, he was going to be able to manhandle it."
In 1966, the two were in the lead at the last turn of 12 Hours of Sebring, an endurance race in Florida, when their engine failed. Gurney pushed the car to the finish, but they were disqualified because cars had to finish the race under their own power.
Grant raced in the Indianapolis 500 10 times. In the 1972 race, driving an Eagle-Offenhauser customized by the All American Racers, Grant took the lead when Gary Bettenhausen had to leave the race. Grant had nearly lapped Mark Donohue, the eventual winner, when he pulled into the pit to have a front-wheel vibration fixed. His teammate Bobby Unser had already left the race, and the pit crew waved him into Unser's spot. They changed his tire, and one crew member put fuel from Unser's tank into Grant's even though using fuel from another racer's tank violated the rules.
Grant finished second in the race, but the United States Auto Club ruled that his last 12 laps would not count. He was dropped to 12th place in a field of 33.
Later that year, Grant was qualifying for the California 500 at the Ontario Motor Speedway when his engine man asked if he wanted more horsepower.
"Well, that's like asking a drunk if he wants another drink," Grant told the motorsports journalist Gordon Kirby.
Before a crowd of more than 60,000, he went on to become the first driver to exceed 200 m.p.h. in an Indy-style car. Grant pushed his Eagle so hard that it turned the corners sideways in three of his four qualifying laps. His first three laps were all faster than 200 m.p.h. Gerald Wayne Grant was born on Jan. 23, 1935, in Seattle, to Glen and Hazel Grant. He graduated from Seattle High School and studied engineering at a community college before serving in the Army during the Korean War. He got involved with hot rods as a teenager and sports-car racing later on.
After retiring, Grant was a vice president of Champion Sparkplugs and did public relations work for Honda. He lived in Irvine, Calif.
In addition to his daughter, Grant is survived by his wife, Sandra; a sister, Marcia Kunz; a daughter, Tammy Grant; and five grandchildren.
Never one to take it slow, Grant was also an avid boater, motorcyclist and aerobatic pilot. He last rode his motorcycle, a BMW R1200R, on July 12.