Big Cummins Diesels Come To The Indianapolis 500

By
– Posted on June 14, 2023

Cummins Indy color

(first posted 5/24/2013)    One of the more unique chapters in the colorful history of the Indy 500 was written by Clessie Cummins, the irrepressible founder and promoter of his pioneering diesel engine manufacturing company. Getting cheap-gas swilling Americans interested in the diesel engine was a challenge, one Cummins took up in a number of ways, including endurance and cross-country runs in diesel-powered trucks, buses and even a big Packard. But the most ambitious ones were his several assaults on Indy, spanning some twenty nears, no less. It culminated in 1952, when driver Fred Abagashian put this sleek lay-down Kurtis roadster on the pole, with a  record-setting 138.010 mph black-smoke-belching run.

cummins diesels-assaulted-indy-inline-1-photo-448618-s-original

The first attempt was in 1930, when Cummins took advantage of the new “junk” formula that allowed stock-block engines up to 6 liters (366 cubic inches). A 361 inch four cylinder marine engine making some 85 hp was adapted to a modified Duesenberg Model A chassis, resulting in a car that weighed a hefty 3389 lbs, which may be a record for Indy. It qualified at 96.871 mph, slowest in the field.

The strategy was to run the race without a pit stop, which had never been done before. And it worked: the slow but steady Cummins Special worked its way up to a 13th place finish, averaging 86.170 mph, and netting a spectacular 16 mpg in the process. The engine used one quart of oil, and the total fuel and oil bill for the race was $2.40! Just the ticket for a Depression-era run at Indy.

cummins-diesels-assaulted-indy-inline-2-photo-448619-s-original

Number 8 was fitted with headlights, windshield, a folding top, and side-mounted trunk, and was shipped to Europe where Cummins drove it 5000 miles, demonstrating its prowess, efficiency and durability on public roads and on race tracks. It must have all helped, as Cummins began to make some inroads into the truck and bus market, after being limited to mostly marine engines.

cummins diesels-assaulted-indy-inline-3-photo-448620-s-original

In 1934, there was a massive internal debate at Cummins as to whether the future of the diesel engine was two-stroke or four-stroke (Cummins engines so far were all four stroke). So to test the competing designs, Cummins built one of each for the 1934 race.

The four-stroke racer dropped out due to a broken transmission. But “Stubby” Stubblefield pushed the two-stroke hard, despite violent vibrations and a burned foot from a red-hot transmission. Number 5 managed a 12th place finish, the highest ever for a diesel.

But as the all-aluminum two-stroke cooled off after the race, it contracted and froze up solidly, and Cummins had it removed and tossed off a bridge into the White River at night. Cummins never built another two-stroke again. And I wonder if someone will try to find that engine and salvage it? Or just scrap it.

Cummins _Diesel_Roadster

In 1950, in order to promote Cummins’ new six-cylinder four-valve truck engine, a new roadster was commissioned from Frank Kurtis, with a lengthened wheelbase to accommodate the big oil-burner. A magnesium block and aluminum head lightened the Rootes supercharged 401 cubic incher, but it was still top-heavy. And after fifty laps, its vibration damper came loose, forcing an early retirement.

Cummins _diesel_at_the_indy_500+1952_indy_500

The final assault came with this sleek new roadster, which was the first to have a “lay down” engine, with the block five degrees from horizontal, and the drive shaft offset to pass alongside the driver. This was a radical new configuration, first conceived of as a solution to the tall diesel engine, but one which was quickly picked up and soon became ubiquitous due its lower center of gravity and superior aerodynamics.

The 380 hp NHH six also pioneered turbocharging at the brickyard, then referred to as a “turbo-supercharger”. It quickly became apparent that this low-slung diesel rocket had enormous potential. Sure enough, on Pole Day, Saturday May 17, the Cummins turned into an orange streak as it set new all-time lap records and qualified for the pole position, with a four lap average of 137.002 mph. Thanks to its chunky 3100 lbs, the two left tires were in tatters.

The Cummins ran well, as high as fifth place, but couldn’t really keep up with the much lighter cars in the lead. Then on the 70th lap, the diesel began spewing a huge cloud of black smoke, and Abagashian headed for the pits. It was all over, thanks to the turbocharger inlet having digested too much road debris, due to its unprotected location down low. This is why new cars rarely win: the trials and errors have to be learned the hard way.

cummins diesels-assaulted-indy-inline-4-photo-448621-s-original

After the race, Number 28 was placed on display in the Cummins headquarters lobby, and sent to car shows. There was no thought of going back in 1953, one of the reasons being that the Indy run had done its job: sales of Cummins engines surged, and marked the beginning of the end of gas-powered heavy trucks.

In 1969, for Cummin’s 50th anniversary, the engine was finally torn down to prepare the car for a big bash at the speedway and other events. It turns out that there was a large crack in the crankshaft, which would undoubtedly have failed within a few more laps. All witnesses were sworn to secrecy.

The lay-down engine as used in Number 28 led directly to Cummins famous “pancake” diesel engines, which were horizontal inline sixes used extensively in buses, under the floor in the middle of the vehicle. Crown and Gillig school buses used these for decades, as well as others. Race on Memorial Day; haul kids to school on Tuesday.