the caution flag flew for the first time. Al Unser, Sr. made a routine pit stop, but a fire broke out in the turbocharger. He was able to return to the race, but after only one lap, he lost a wheel and hit the wall in turn one. Arnie Knepper and Gary Bettenhausen were also involved. After , defending champion A. J. Foyt was out with a blown engine. Second half On lap 110, Graham Hill lost a wheel and smashed into the turn two wall, which brought out the second caution. It was the first of the three Granatelli Turbines to drop out of the race. On the restart, Bobby Unser took the lead, blowing by Joe Leonard, showing the traditional piston-powered engines were still a match for the powerful turbines. On lap 127, Mel Kenyon and rookie Billy Vukovich II tangled in turn four. Both were able to re-enter the race, but Johnny Rutherford, while trying to slow down, was rear-ended by Jim McElreath. Mike Mosley also spun into the turn four grass trying to avoid the accident. Rutherford was out, but McElreath limped back to the pits where his crew repair the nosecone. When Bobby Unser made his last pit stop on lap 166, his gearshift linkage was broken, and the car was stuck in high gear. As he slowly left his pit, struggling to accelerate back to racing speed, both Leonard and Ruby passed him. Leonard now led in the Turbine. Ruby was up to second, but moments later on lap 178, Ruby was back in the pits with a faulty ignition coil. His crew was able to replace the coil, but the six-minute pit stop dropped him out of contention for the win. With 19 laps to go, Joe Leonard led, with Bobby Unser back up to second. Carl Williams crashed on the backstretch, triggering a fire which brought out the yellow light. Under the caution, Leonard led, with Bobby Unser second, and Dan Gurney in third. For a brief moment, a controversy started brewing as Art Pollard (teammate to Joe Leonard), who was a couple laps down, was not keeping up with the caution pace. As a result, Bobby Unser was stuck behind him, and losing track position to Leonard. Finish After the cleanup, the green flag was given to the field at the start of lap 192. At that instant, both leader Joe