1968: The Granatellis return with even more turbines this year, in new wedge-shaped Lotus chassis. They take the first two starting spots with record speeds of over 170 mph. However, on race day, Bobby Unser in a turbocharged Offenhauser-powered car, is able to take their measure, leading 127 laps. Unser's path to victory is cleared when Joe Leonard's turbine breaks its fuel pump shaft with just nine laps to go while leading. USAC then issues further restrictions on turbines, rendering any future such engines uncompetitive.