After a thirteen-year absence, Cummins Engine Co. returned to the Indianapolis 500 in 1950 with the “Green Hornet.” The racer was a modified Kurtis Kraft chassis powered by a supercharged 401 cubic inch diesel-powered engine based on the Cummins JBS 600 truck engine. The engine, which produced 320 horsepower, had four valves per cylinder and used an aluminum crankcase, cylinder block and head. The car had disc brakes, a first at Indy. The car used an early design of what would become Cummins PT (pressure-timed) fuel injection system.
Because of its green color, its driver, Jimmy Johnson named it the “Green Hornet.” On May 27th, Johnson was running some practice laps after the car was trucked from the Cummins factory in Columbus, Indiana. On the first lap, the racer hit an estimated 150 mph on the main straightaway. Then, the head gasket blew, and the car had smoke pouring from the engine as it pulled into the pits. The next day, the racer qualified last on the starting grid with a speed of 129.208 mph. The pole sitter was Walt Faulkner with a qualifying speed of 134.343 mph. The field was the fastest starting lineup in the Speedway’s history.
Cheered on by Cummins employees estimated between 500 and 1,000, the car’s Indianapolis 500 run ended on lap 52 when the supercharger shaft broke. At the time, the car was running three laps behind the leader with an average speed of around 120 mph. While the car was out of the race, Cummins officials were pleased with the performance of the engine. Johnny Parsons won the rain shortened race after 345 miles.
The “Green Dragon” was repaired and set six international diesel speed records at the Bonneville Salt Flats in September. The records were for one kilometer (163.82 mph), one mile (164.23 mph), 5 kilometers (164.25 mph), five miles (161.92 mph), 10 kilometers (147.3 mph) and 10 miles (148.14 mph).
In 1951, Cummins Engine decided to make another attempt at the Indianapolis 500 in 1952. The rules allowed for a diesel engine as large as 6.6 liters as compared with a three-liter limit for supercharged gasoline engines. Working with Frank Kurtis of Kurtis Kraft, the chassis of the # 28 car was low-slung. Cummins installed an engine based upon the one used in the “Green Hornet.” By laying the engine nearly on its side, the profile of the car was very low with the cowling being about 23 inches above ground.
Unlike previous attempts at the Speedway, early testing indicated this car was very fast. The driver, Freddie Agabashian, was careful not to reveal the car’s true potential as Cummins was afraid that the car could be banned if its true capabilities were known. Fifteen minutes before the end of qualifying on Pole Day, Agabashian took the car out and set a one-lap record at 139.104 mph and a four-lap record of 138.010 mph for the pole. During the qualifying effort, Agabashian nearly shredded the right-front tire tread. His qualifying speed was short lived, as two cars later qualified with faster speeds (Bill Vukovich at 138.21 mph and Chet Miller at 139.03 mph).
Race day was disappointing. The car had a problem with dirt and tire debris clogging the charger intake. The turbocharger failed on lap 71. Agabashian was in fifth place at the time he dropped out. The car finished in 27th place. After the Indianapolis 500, the rules were changed. The Cummins Diesel Special was the last diesel-engine car to compete in the Indianapolis 500.
As part of the celebration of Cummins’ 100th anniversary in 2019 and a nod to its role in the Indianapolis 500, the five Cummins racers (1931, 1935, 1950 and 1952) were part of the pre-race parade.