Gordon Johncock joined U.E. "Pat" Patrick and George Bignotti at Patrick Racing for the 1973 USAC Championship Trail. Although Johncock topped 199 mph during March tire tests at the Brickyard®, Brickyard®,during qualifying he ran 192.555 mph to get the 11^th starting position. A first-lap mishap involving several cars, followed by heavy rain, caused a postponement until the following day. On the second day, rain began during the parade lap, and the green flag was never shown before the race was red-flagged and postponed again. When the race finally got under way on the third day, Johncock began moving up quickly.

When early leader Bobby Unser pitted on Lap 39, Johncock took the lead for three laps until he too, had to pit. Johncock's team mate Swede Savage had an accident on Lap 58, stopping the race for more than an hour. After the re-start, Al Unser led from Johncock and Bill Vukovich, Jr., the only three drivers on the lead lap. Al Unser slowed on Lap 73 then stopped with engine problems two laps later. Johncock assumed the lead, with Vukovich second and Bobby Unser third, one lap down. Although Vukovich closed to within 6 seconds at one point, he was unable to challenge Johncock's lead, which later grew to 31 seconds. On Lap 100 Johncock set the fastest lead lap of the race, 184.805 mph. A rain shower on Lap 129 brought out a yellow flag. As the rain fell harder, the red flag was shown to Johncock on Lap 133. A few minutes later the race was called. Vukovich finished second, still on the lead lap, ahead of Roger McCluskey in third, two laps down. Gordon Johncock won the 1973 Indianapolis 500® at an average speed of 159.036 mph.