The Indy 500 is a famous big race in the U.S. for open-wheel cars. It’s a place where teams test new engineering ideas because the competition is intense and the rules matter a lot.
Cummins is a company that makes diesel engines. In this story, they’re not just building engines for trucks—they also tried to win at the Indy 500 and helped shape how race teams develop engines.
“Qualified on the pole” means the car was the fastest in qualifying and starts in the first spot. Starting up front helps you avoid getting stuck in traffic right away.
A diesel engine runs by compressing air so much that the fuel ignites from heat, not from a spark plug. That can change how the engine makes power and how long it lasts.
Concept
rulemaking authority response and racing in effect of ban
This refers to governing bodies changing or enforcing rules to limit a technology after it becomes too dominant. In motorsport, bans or restrictions often follow rapid innovation, aiming to keep competition fair and control performance.
Term
power, refinement and durability
The host is talking about three things engines are judged on: how strong they are (power), how smooth they feel (refinement), and how long they keep working without failing (durability).
These are two key engine measurements: bore is how wide the cylinder is, and stroke is how far the piston moves. Changing them changes the engine’s size and how it makes power.
Ray Haroon is the driver the host mentions as winning the very first Indy 500. He’s part of the story that leads into how the racing world evolved over time.
Brand
Marmin
Marmin is the company the host says Klessy worked for. It’s tied to the race team that built and entered the car from the factory.
William Irwin is the wealthy person in this story who helped pay for Cummins when it wasn’t yet making money. He kept the company going while the engineers worked through problems.
Fuel metering means controlling how much fuel the engine gets. In diesel engines, that control is crucial because too much or too little fuel can make the engine run poorly.
Needle valves are small, precise valves that help control fuel flow inside a diesel engine. A good seal helps keep fuel from leaking and helps the engine get the right amount of fuel.
This is how a diesel engine sprays fuel straight into the cylinder. Instead of computers controlling it, mechanical parts handle the timing and pressure, which helps the fuel burn more cleanly.
Some older diesel engines used a small extra chamber to help get the burning started. Fuel would go there first, and then the main cylinder would do the rest.
Pressure lubrication means the engine uses a pump to push oil to the moving parts under pressure. That helps protect bearings and other parts from wear.
Reciprocating parts are the pieces that move back and forth inside the engine. Enclosing them can help keep things cleaner and better protected.
Car
1925 Packard touring car
The host mentions a 1925 Packard touring car as an example of the kind of vehicle Cummins wanted diesel power to work in. It’s basically a specific old car used to set the scene.
The New York Auto Show is a big public car event where companies show off new vehicles. Here, the story is that the car was displayed outside the show to get attention anyway.
Person
K-Don
K-Don is the “speed-seeking” British person mentioned here. The hosts say he was going to try for a world land speed record at Daytona, and that created an opportunity for Cummins.
Daytona is where the segment says the land speed record attempt would happen. It’s described as a beach setting where speed runs are made.
Car
Model U
The Model U is an early Cummins diesel engine. The hosts say it was efficient enough that truck operators started paying attention, and it helped Cummins become successful in trucking.
Indianapolis Motor Speedway is the track where the Indy 500 is run. It’s a big deal in racing, and this story says Cummins got pulled back there because the rules changed.
Eddie Rickenbacker is the person in the story who owned the race track. He changed the race rules so production-style engines could compete, which helped Cummins.
This phrase means the race allowed engines that were based on engines you could buy or that came from normal production. It wasn’t limited to only custom-built race engines.
A displacement limit is a rule that caps how big the engine is. Here, the race limited it to 366 cubic inches, and Cummins tried to modify their engine to fit that limit.
Qualifying runs are practice/timing sessions right before the race where you prove you’re fast enough to start. In this story, the car had to hit over 80 mph during qualifying.
Shocks (like Gabriel shocks) control how the suspension moves over bumps. “Dual” means there are two shocks working instead of one, which helps the car handle the extra weight.
That “366 cubic inch limit” is a rule that caps the engine size for the Indy 500. If your engine is bigger than that, you can’t race it, so builders redesign the engine to fit the limit.
An inline four is an engine with four cylinders lined up in a row. Here, it was used because it helped the builders fit the Indy 500 engine-size rules.
RPM means how many times the engine spins each minute. Higher RPM usually means the engine is working faster, and this story emphasizes that the diesel could rev unusually high for its era.
Compression ratio is how much the engine squeezes the air/fuel mixture inside the cylinder. Diesel engines need enough squeezing to ignite the fuel reliably, so this number affects power and smoothness.
Cylinder pressure is how hard the engine’s combustion chamber is “working” inside. In a diesel, higher pressure helps ignite the fuel and can improve how completely it burns.
A ram air setup uses the car moving fast to push extra air into the engine. More air can help the engine burn fuel more completely, which can mean more power and less smoke.
A ram tube scoop is a shaped intake duct that grabs air while you’re driving and feeds it toward the engine. The goal is to get more useful air into the intake so the engine can burn fuel better.
The intake manifold is the part that spreads incoming air to each cylinder. If more (and better) air reaches it, the engine can burn fuel more completely.
Complete combustion means the fuel burns more fully instead of leaving soot or unburned stuff behind. On diesels, that usually shows up as less smoke from the exhaust.
Columbus, Indiana is where Cummins is based (at least in this story). The host mentions it to show how they could drive the car to test it near the track.
A flying mile is a speed record where the car is moving before the measured mile starts. The clock is only for that mile, so it’s a way to measure top speed more fairly.
A slide rule is a handheld calculator tool that people used before digital calculators. Here it’s used to show he predicted the car’s speed using math ahead of time.
The Indianapolis 500 is one of the biggest and most famous races in the U.S. This part of the story is about a diesel-powered car trying to compete there and finishing strongly through strategy and efficiency.
Dave Edwards was the driver of the Cummins diesel car at the 1931 Indy 500. The episode credits him with helping the car finish well by staying out of trouble and keeping it running.
Fuel economy means getting more miles out of each gallon of fuel. In a race, better fuel economy can help you spend less time refueling and more time driving.
Pit stops are when race cars pull into the pit lane during the race. They’re used for things like refueling or quick repairs, and they cost time.
Term
combustion styles
Combustion is how the engine burns its fuel. “Combustion style” here means the engines were designed to burn fuel in different ways, even though they shared some basic dimensions.
General Motors is mentioned because their earlier diesel work (a two-stroke Detroit diesel) was seen as successful. Cummins used that as inspiration for their own competing engine designs.
A four-stroke engine works in four steps as the piston moves: it sucks in air/fuel, compresses it, burns it to make power, then pushes the exhaust out. In this story, Cummins built one car with this type of engine and another with a different design.
A two-stroke engine makes a power cycle in fewer steps than a four-stroke. Instead of separate intake and exhaust strokes, it uses ports and piston movement to manage airflow, and here Cummins was experimenting with that design.
Engine displacement is a measure of how much space the pistons move through inside the cylinders. It’s a way to compare engine size, and here both engines are described as having the same displacement.
“Square” bore and stroke means the cylinder is about the same size as the piston’s travel distance. That design choice can influence how the engine performs and how easily it can spin faster.
A cylinder head is where the valves live. “Two-valve” means each cylinder has two openings (usually one for intake and one for exhaust), which affects how the engine breathes compared with other valve/port designs.
Instead of using an intake valve, this engine uses openings (ports) in a sleeve. As the piston moves up and down, it reveals and covers those ports to let air in at the right time.
A camshaft controls when the engine’s valves open and close. “Side-mounted” just means the camshaft is located on the side of the engine, and here it’s part of how both Cummins engines were built to run their valve timing.
A supercharger forces extra air into the engine so it can burn more fuel and make more power. The podcast is comparing how much power that air-pumping system costs in different engine designs.
Scavenging means getting the old exhaust out of the cylinder and bringing in fresh air (and fuel). In a two-stroke engine, that job happens differently and is part of why the blower has to work harder.
The transmission is the part that sends power from the engine to the wheels using gears. The podcast claims it broke because the car was launched too aggressively after the pit stop.
Wild Bill Cummings is the driver who tried to set diesel speed records at Daytona. The podcast notes the attempts weren’t officially certified, but they still showed diesels could go very fast.
“OE options” means the engine is offered through the vehicle maker itself, like a factory-installed choice. The podcast says Cummins got their engines into trucks the “official” way, not as aftermarket parts.
A clean sheet design means they didn’t just tweak an old idea—they started fresh. It’s used when the new goal is different enough that a new approach makes more sense.
A supercharged engine uses a device that forces extra air into the engine. That extra air helps the engine make more power than it could with just normal air intake.
JBS-600 is the name Cummins used for a particular version of its engine. It tells you which design family it belongs to and, in this case, that it’s a supercharged six-cylinder.
This describes how the engine opens and closes its valves. “Two-valve” means each cylinder has one intake and one exhaust valve, and “pushrod” means the camshaft uses rods to operate them.
Torque is the engine’s pulling force. More torque (especially at lower rpm) usually feels like better acceleration and easier driving in everyday situations.
This is a promise that the company will stand behind the truck/engine for a long distance—here, 100,000 miles. It’s meant to reduce buyer risk when trying a new product.
Spark ignition means the engine uses a spark plug to light the fuel. Gasoline engines typically do this, unlike diesel engines which ignite from compression heat.
Aluminum is a lighter metal than many traditional engine materials. Using it can help an engine handle higher speeds and heat better.
Term
BMW P
“BMW P” is mentioned like a benchmark engine or reference point. The speaker is saying the diesel needs to beat that kind of power number to be competitive.
The BMW 3 Series is a luxury car that’s meant to be comfortable for daily driving but also fun to drive. People often talk about it when they want a certain amount of engine power, because it has versions that can be tuned or built for higher performance. It’s usually discussed as a “performance-capable” everyday sedan.
Connecting rods are the parts that connect the piston to the crankshaft. They have to handle huge forces at high RPM, so if they’re not strong enough, the engine can fail.
The valve train is the set of parts that controls when the engine’s valves open and close. At high RPM it has to move correctly without floating or breaking.
Car
JBS 600
This “JBS 600” is the specific engine Cummins was building and testing for the Indy 500 program. They put it on a dyno (a machine that loads the engine) to see if it could handle very high RPM without breaking.
Main bearings are the crankshaft’s support points inside the engine. They need oil to keep the crank from grinding against the metal housing, especially at high speed.
Rod bearings are the bearings that help the connecting rods move smoothly on the crankshaft. If they don’t get enough oil, they can overheat and fail quickly.
This is an extra oil pump powered by a motor. Its job is to push more oil through the engine so the bearings stay lubricated when the engine is working very hard.
Oil pressure is how strongly the engine’s oil is being pushed through the system. Higher pressure usually means better lubrication, which helps prevent parts from overheating and wearing out.
A belt drive is a way to transfer motion using a belt. In this case, the way the supercharger was driven by belts led to bearing problems, so they redesigned the setup.
A viscous dampener is a vibration absorber that uses fluid to calm down shaking. Spinning parts can vibrate at certain speeds, and this helps keep those vibrations from getting worse.
They redesigned the wrist pin with thicker walls so it’s stronger. It’s a bit heavier, but it’s necessary when the original pins keep cracking at high engine speed.
Piston clearance is the small space between the piston and the cylinder. They adjust it because the piston gets bigger when hot, and too little clearance can cause rubbing or failure.
This is the top part of the engine that controls how air and fuel get in and exhaust gets out. “Four valve” means there are more openings per cylinder, and “cross flow” means the intake and exhaust paths are arranged to flow more efficiently. The episode says Cummins used this kind of head to make more power.
Swirl is when the air inside the engine spins as it’s being compressed. Engine designers often try to create that spinning motion because it helps the fuel burn better. The host says Cummins got faster even when they had little to no swirl.
Squish is the way the piston squeezes the air in the cylinder near the end of compression. That squeezing can help the burn happen more effectively. The host says their setup worked even with almost no squish.
On a diesel, the fuel has to be injected under high pressure at the right moment. The injector pump cam helps control that timing and how the pump works. Here, the host says they reworked it for better results.
Injection timing is when the diesel injects fuel during the engine’s cycle. If it happens too early or too late, the burn won’t be as effective and the engine can feel rough or stressed. The host says they tested different timing and landed back near the stock timing.
Valve float is when the engine spins so fast that the valves can’t move exactly as the camshaft intends. When that happens, the timing can go wrong and the valves may not clear the pistons. The host says they fixed it by changing the cam design and using stronger valve springs.
High-speed cameras record video much faster than normal, so you can see quick mechanical movements clearly. The episode says Cummins used them to study how the valve train was behaving at very high speeds. It helped them understand what was happening inside the engine.
An iron engine is built with iron parts, which are heavier than aluminum. The host says they used an iron engine for the tests because the aluminum version wasn’t ready yet. It was a practical step to keep development moving.
In a pushrod engine, there’s a small gap in the valve mechanism. Heat makes metal expand, so the gap changes while the engine runs. Mechanics set it correctly at operating temperature so the valves open and close properly.
LIVE
It's a seemingly odd pair of things to have in the same sentence.
Cummins diesel and the Indy 500.
What could they possibly have in common?
What's there to know about this?
The hardcore history freaks will tell you that in 1952 a Cummins diesel powered car
qualified on the pole for the race.
But even those hardcore's may not know it was the fifth car with the fifth different engine
in it the company had used to compete at the Indy 500 with over the years and their history
dates back to the very first Indy 500 in 1911.
In fact, I'm going to stand on business here and say that Cummins is the single most innovative
company in the history of the Indy 500.
Now this is how and why with historical receipts the Cummins engine company over the
course of two decades, five cars and again five engines tried, innovated and experimented with
more concepts both mechanically and otherwise than all others combined between 1931 and 1952.
More than that, the work they did in this arena created the standard for modern race teams
and race car development as it is still done today.
This is not simply the story of the 1952 Cummins diesel special that qualified on the pole of
the Indy 500.
This is the story of the cars, the engines and the engineering that culminated in that
historic effort, one that was met by the typical rulemaking authority response and racing
in effect of ban.
This is also the story of how one company truly used racing to transform an entire industry
and the technology in it.
There were diesel engines before the Cummins racing experiments but the ones that came
after it were of a different league in power, refinement and durability.
Just to not waste your time or mine here, I'm concentrating on the racing side of the Cummins
story.
The company history which is rich with trials, tribulations and fantastic tales,
others have told those on this platform and likely have done a better job than I ever could.
As best I can tell though, at least here on this platform no one has taken you into the true depth.
We're going down to nuts and bolts and bores and strokes and power radders and blowers and
all that type of stuff into the Cummins racing story.
Again, the 1952 Indy 500 pole is a big part of it but that moment was decades in the making.
So with all that being said, let's get on with the show.
Tuesday, May 30th, 1911 was a day that has forever stamped an American auto racing history.
That is the day of the first Indy 500.
As trivia buffs will tell you, Ray Haroon won the contest driving a Marmin Wasp race car.
Less well known is that among the men on his crew was a hard working,
mechanically gifted kid, employed at Marmin and tagged by his bosses to be on the racing
team that fielded this car from the factory.
He was 22 years old and while the Speedway awed him for its size and grandiosity,
the feeling he and his team had in the winner's circle stirred something deep within his soul.
Klessy Cummins was the young man's name and he knew there was more for him in the world
than the job at Marmin.
And at this point in his life, the furthest thing from his mind were diesel engines.
In fact, he had physically never seen one at this point in his life,
but he understood one foundational thing about that moment in the winner's circle.
Klessy Cummins would be back at the Speedway one day and when he was,
he would be there of a car of his own.
Somehow, it would take him exactly 20 years.
The early history of the Cummins oil engine company is interesting,
tumultuous and really less influenced by Klessy Cummins and in so many ways more dependent
on a man named William Irwin.
Irwin was a gargantuanly wealthy guy who not only funded the creation of the company,
but swallowed many years of losses and some failed ideas to keep the thing floating.
Irwin believed strongly in the mechanical brilliance of Klessy and his vision for
the company and he was certain that these things would work,
but it certainly would take a lot longer than he had ever planned or perhaps expected to.
After working with other companies and building diesel engines under license,
Cummins released the first commercial engine of the company's history, the Model F in 1924.
These were large industrial engines, a five and a half inch bore and seven inch stroke.
They were stationary things.
They ran large pumps and generators.
Some landed in fishing boats and yes, many went on to power lighthouses.
It was an okay seller and established Cummins as the maker of a quality product,
but it wasn't the smash hit they were looking for.
Klessy's vision for the company was one where his engines would be powering high end luxury
passenger cars, effectively becoming a supplier to one or many of the high dollar brands.
Irwin had a likely more practical vision, hence these forays into industrial engines
to establish the company name.
Cummins for his part was a true mechanical genius and visionary.
He had an acute understanding of the inherent issues holding diesel engines back in the 20s
and he set forth to effectively deal with them one by one and it started with fuel.
At this time, most diesel engines were using needle valves to handle fuel metering.
The valves would seal in a seat.
The needle would effectively be displaced by fuel pressure and then the fuel would be
injected into the cylinder at 50 psi or so.
These numbers could vary, but this is ballpark stuff.
The system wasn't very accurate, certainly not optimal for making thicker and heavier
diesel fuel atomize in the air for combustion and it was the first thing that Klessy Cummins
truly attacked.
Over the course of a five year span, Cummins made some 3,000 prototypes to develop an accurate,
precise and practical mechanically controlled direct injection system for diesel engines.
The needle valves were gone and his fuel injectors replaced them.
Gone were the wimpy 50 psi of fuel being injected into a pre-combustion chamber
and here was fuel being shot into the cylinder at 5000 psi, atomizing and burning more completely
than ever before.
This truly was the world's first practical direct injection system.
For his follow-up act, Cummins would change the mechanical world.
The engine was called the Model U.
Unveiled in 1928, the world had not seen a diesel engine like it before.
It was fully pressure lubricated.
All of its moving and reciprocating parts were fully enclosed, which was an actual first for
a diesel engine.
It was modular in its construction, meaning it could be had from a one cylinder to an
inline six if you'd like it that big.
And it made a theretofore shocking 10 horsepower per cylinder and perhaps more importantly,
it featured his direct injection system.
This engine, aligned with Cummins vision of powering automobiles so he tapped Irwin on
the shoulder, pointed to a used 1925 Packard touring car and explained to Irwin how this
was going to be their literal promotional vehicle.
The Model U's initial target audience was mostly marine and for small and medium-sized
boats.
Klessy knew the best way to promote this engine wasn't on the water though, it was on
the road.
Out came the reasonably large Packard straight eight and in went the Model U four cylinder
that absolutely dwarfed the factory engine and physical dimension.
I'm guessing that there was a lot of measuring done before the 1925 Packard was selected
because the Model U cylinder fit in it barely.
Testing and refinement work was done in 1929 and then in 1930 a public debut was made at
the New York Auto Show.
Two things made this notable.
The first is that he was not allowed into the New York Auto Show so he displayed the car
across the street and kind of stole the thunder from the whole event and then people learned
he had driven the car 600 miles to the event to display it, raising the hype level even further.
But the thing that really drove people wild was the fact that the 600 mile ride
had cost him a total of $1.38 in fuel and like the 3000 prototypes that $1.38 is the
real number.
Now not long after the show Cummins got word that K-Don, the speed-seeking Brit would be
on the beaches of Daytona trying to set the world's land speed record.
With that came the opportunity to enter the fray and attempt to set some production car
style records.
He hopped into the car, snagged a factory mechanic and made tracks self.
The goal was simple.
Proved to the world that diesel engines were not just for fishing trawlers and stationary
applications.
These things could boogie too.
With a trail of black smoke behind him and his Model U engine turning away,
Klessy Cummins went more than 80 miles per hour to the astonishment of many people there.
And what was so impressive about this was the fact that it became the fastest diesel powered
anything in the world.
He had just set the world mark for diesel performance on his own and then he put his
stuff in the trunk of the car and drove it home.
It was another publicity bonanza.
The speed was one thing but the headlines touted the simply miraculous fuel economy
that the Packard had achieved.
The car traveled 2,250 miles for a total of $4.87 in fuel cost.
The Model U was officially set to become the world's first consumer diesel engine.
The hype, the economy, the headlines and the speed had it placed at all exactly where
Klessy had always imagined it could be and would be at exactly the wrong time.
Five months before Klessy Cummins set speed records on the Daytona Sands,
the stock market had crashed and the world's economic system was starting to crack at the
foundation.
Additionally, Cummins had no means to mass produce the Model U.
In a way he was banking on a car company licensing the design and using it for their cars.
Rather than take orders for engines he could not make, Cummins set forth on creating the
infrastructure to mass produce the Model U as the bottom was beginning to come out of the economy
and the auto industry as a whole.
Irwin showing a kind of dedication, vision and loyalty that scantly seems to exist anymore
agreed to keep backing Cummins despite the tough economic conditions
and he managed to keep the company out of bankruptcy.
As the hopes of selling engines to high-end and luxury car makers faded with each company's
financial failure, a market no one had thought much about came knocking, the trucking industry.
Even a hundred years ago, truck fleet operators were vigilant about fuel economy.
It's an incremental expense that can sink the entire operation.
The efficiency of the Model U got their attention and its power output seemed good enough.
When Cummins talked Irwin into retrofitting a truck fleet of a supermarket chain that he owned,
the results and proof of concepts saw the popularity of the engine skyrocket in the
trucking industry and their rise to become a dominant force in the trucking world had begun.
But Klessy Cummins was a racer and in 1931 the Indianapolis Motor Speedway was calling him back.
Twenty years after that warm Tuesday afternoon in the Marmin Wasp's glorious victory.
The path that Cummins returned at Indy was actually paved in 1930 when Eddie Rickenbacker,
who owned the track, changed the rules for the race allowing stock production block engines in.
The move of course motivated by the ever-growing malaise of the Great Depression
and the ever-shorting budgets of race teams. The displacement limit was 366 cubic inches
and Cummins knew that with some changes he could get a Model U to that size.
Cummins employing all of his sales and pitch skills went to Rickenbacker and the World War
1 flying ace accepted his idea. He got a guaranteed spot in the race if the car could
make more than 80 miles per hour in qualifying runs. But there was a catch. No matter how well
the car did, it could not earn any prize money. With the Model U starting to show signs of business
promise, Cummins convinced Irwin to allocate company funds for a race car and Irwin did.
The men contacted the Duesenberg brothers in order to customize version of their model
a race car chassis. With the massive weight and size of their engine, the body was kind of built
around the power plant. The chassis itself was upgraded with heavier duty springs and dual
Gabriel shocks at all four corners and it was a behemoth of a car. 16 feet 8 inches long,
which was 4 feet longer than most of the other cars at the race, 5 feet 10 inches wide, about
a foot wider than anybody else's car and well over 3,000 pounds that outweighed everybody
else by half a ton minimum. Klessy went to work on a special version of the Model U.
The typical bore of the engine was 4.5 inches or 114 millimeters, typical stroke was 6 inches or
152 millimeters. To get it to under the 366 cubic inch limit, he went with a four cylinder engine
of 4.375 inch bore or 111 millimeters, which was a reduction of 125 thousandths of an inch
and he maintained the stock stroke of 152 millimeters or six inches. This was a 361 cubic
inch inline four. Now a special cylinder head using two intake and one exhaust valves was
crafted and bolted on, aluminum pistons were added and multiple camshafts were tried to get the
maximum power right of the RPM, not multiple camshafts in the engine, just multiple grinds of
camshafts. The compression ratio was still quite low as compared to the modern diesel because it
was only generating 500 psi of cylinder pressure, so it was likely no higher than 11 to 1. But the
result was an engine that made 85 horsepower at 1800 rpm and weighed 1600 pounds. Outside of this
being the first diesel to ever run at the Indy 500, it was also the first car to employ a ram air setup.
Klessy had designed an interesting kind of ram tube scoop that passed through the radiator and made a
straight shot into the intake manifold. His theory, which was correct of course, was that the high
velocity air would help charge the engine and make more complete combustion possible. He was
proven correct in testing because after the scoop was added, the amount of smoke greatly diminished
indicating more complete combustion, a completely free supercharger if only
nominally as effective as a mechanical one. The most mind-blowing thing to people was that this
diesel could rev to 2000 rpm. A few years before, 500 rpm was pushing it to the extreme with any
diesel engine and Klessy's math said at 2000 rpm, this car should run about 100 miles per hour.
He then tested the literal wheels off this thing. Cummins based in Columbus, Indiana was only 45
miles from the speedway and they actually drove the car back and forth on public roads and tested,
and tested, and tested. But it wasn't always race cars on the speedway with Cummins. In 1931,
he decided to show off how durable his truck engines were by attempting to set a non-stop
driving record. A truck, a large crew and a few drivers showed up at the speedway and started
driving. Coming to a crawl to refuel and even make chassis repairs while the truck was barely moving,
the exercise lasted two weeks, 24 hours a day, non-stop. The truck covered 13,545 miles in that
period showing incredible durability. Also in 1931, speaking to the truckers again,
Cummins installed a Model U into an over-the-road truck, had his factory modify an over-the-road
trailer into living quarters with beds and a stove, and he shipped the whole works to New York City.
He and two other guys got in this rig and headed west. They managed to arrive in Los Angeles 97
hours and 20 minutes after they left New York, which was six hours faster than the previous record.
They also managed an unreal 15.75 miles per gallon on the trip. These efforts, as outlandish as they
seem, started to drive business and the orders started rolling in. As if these things weren't
enough, it needs to be remembered that in February he had driven the Indy 500 race car from Indiana
to Florida and hit the beach at Daytona again. This time he reset the diesel land speed record,
running 100.755 miles per hour in the flying mile, which was exactly what he predicted the car
could do with the slide rule. Cummins was undisputedly the fastest diesel in the world,
and the term high-speed diesel was starting to be used to describe their engines.
Car number 8 at the 1931 Indianapolis 500 was driven by Dave Edwards. Thane Hauser was his
riding mechanic. With a qualifying speed of 96.871 miles per hour, the car was 43rd fastest,
or basically last. But remember, they had a guaranteed starting spot and a massive
ace up their sleeve, which was fuel economy. On race day, the car was driven to the track
from Columbus, Indiana and started a long way from the front. But as time went on, breakage
happened. Other cars were making pit stops left and right. Meanwhile, Evans and Hauser were lapping
consistently, avoiding trouble and climbing the standings. When the checkered flag flew for the
Cummins diesel special, they had finished a mind-boggling 13th and had done something no one has
ever managed before this happened or since this happened. They ran the entire Indianapolis 500
without stopping once. The car got 16 miles per gallon average throughout the race,
the highest fuel economy ever recorded at the event. The speed when they finished was an
average of 86.17 miles per hour over the course of the race, and the car had used
a $1.40 worth of fuel. Well, Clessy wanted a top 10 finish, this was just as good,
and the general public was blown away. Whether it was at the behest of Irwin or Cummins' own sense
of promotional flair, the company came up with a unique proposition to appeal to their core business,
trucking companies. They decided to skip the racetrack that year and hit the open road to
make a point. The exact same car that finished 13th at the 500 was modified with a more posh
interior, a side mounted trunk and other niceties, and was driven all over Europe in 1932 by Irwin
and Cummins promoting and selling Model U engines. Despite everything that was happening to the rest
of the world via the Great Depression, business at Cummins was now booming. Production was topping
100 engines per month, Clessy was able to dedicate himself to research and development,
and that meant another trip to the Speedway. But this trip would be different, there would be
two cars and no guarantees of a starting spot. The two cars for 1934 would not be identical,
though. Seeing the success of the General Motors two-stroke Detroit diesel, Cummins would build
one car with a four-stroke engine and the other with an experimental two-stroke. Once again,
Dusenberg was the chassis supplier, and while the engines would use different combustion styles,
they did have many similarities. Both were to be inline fours with a displacement of 364 cubic
inches. Arrived at by using so-called square bore and stroke numbers of 4.875 inches or 124
millimeters bore and stroke. Both would use roots blowers set in front of the engines and driven
off the ends of the crankshaft. The four-stroke engine used a traditional two-valve cylinder head,
the two-stroke had intake ports in the sleeve that would be uncovered by the piston as it traveled
downward and two exhaust valves in the head. Both engines employed the use of side-mounted
camshafts to open the valves. Interestingly, both engines made 135 horsepower at 2500 rpm
and they both weighed in at a hefty 1,000 pounds. Progress, though. More rpm capability and
significantly less weight than the Model U examples used in 1931. The race cars, though,
they still weighed 3,200 pounds. Another fun fact here is that the Cummins documentation
shows that in the four-stroke application, the supercharger took seven horsepower to turn to
simply supercharge the engine. In the two-stroke application, it took 37 horsepower as the blower
was both scavenging the cylinders and supercharging. Dale Evans qualified 22nd in the four-stroke car.
He used a speed of 102.414. Stubby stubble field driving the two-stroke car qualified 29th
at 105.921. And yes, the slower car actually qualified earlier than stubble field, hence the
slower speed being closer to the front in the 500 things. Running solidly in the upper part of the
field, Evans came in for a pit stop 200 miles into the race. Leaving the pits too aggressively,
the massive torque of a diesel engine fragged the transmission, putting Evans out of the race.
The engine, though, had been flawless and competitive. Stubby field came in for a pit
stop on lap 123 and as that service was being done, the primary team driver, Evans, was swapped into
the seat. Despite some issues, the two-stroke engine went the distance, finishing 12th with an
average speed of 88.566 miles per hour. That said, when it did finish the race, the clattering,
smoking two-stroke engines seized up tight as a drum when Evans pulled into the pits
after all was said and done. This result convinced Cummins to concentrate on four-stroke diesels
for the rest of his days. In 1935, the driver, Wild Bill Cummings, yes Cummings and a Cummins,
went to Daytona and busted off a 133-mile-per-hour flying mile one day and then a 137-mile-per-hour
effort the next. While these were unofficial records and not internationally certified,
they proved again that diesels and speed were words that belonged in the same breath.
Despite the lingering desires of Clessy Cummins to see his engines in passenger cars and seemingly
working to achieve what was a totally pine-the-sky goal, the market dictated to the company what it
wanted and the answer was truck engines. They became a colossus, signing contracts with truck
manufacturers to offer their engines as OE options, which of course was the thing that Clessy so much
wanted to have done with car companies. By 1934, a sales top $1 million per year and by 1937,
the company was turning a true and reliable profit for the first time in its existence.
By 1938, Cummins had 75 percent of the trucking engine market. Cummins piled on the patents
and during World War II, the company made engines for the war effort in huge volumes.
The Indy 500 days were happy but seemingly a distant memory until 1950. Back in 1948,
the Cummins sales department had commissioned a survey of customers to see what the market was
looking for. This survey identified the need for smaller, lighter-weight, high-speed engines for
the exploding medium-duty truck segment. These medium-duty trucks would largely be the support
staff for America's impending post-war economic building and construction boom.
Executives green-lighted a clean sheet design for an engine and the 150 horsepower target range.
By early 1949, it was the top internal project for the company and by the end of that year,
it evolved from the design engineering phase to the production engineering phase,
which is a breathtaking timeline. Known as the J-Series and more precisely the JBS-600,
J-Series, B meaning automotive application and S being supercharged, the 600 being a designation
for six-cylinder, it was a 401 cubic inch inline 6. The engine used a bore of 4.125 inches or 105
millimeters and a stroke of 5 inches or 127 millimeters. The two-valve pushrod engine made
150 horsepower at 2500 rpm and 360 foot-pounds of torque at 1400 rpm. It weighed 1,545 pounds
and made 1 horsepower for every 10.2 pounds of pig iron it was lugging around. In May of 1950,
some pre-production test engines were sent into the field for proving out.
Nine truck manufacturers signed on to offer this engine in their rigs so it was destined
to be a massive seller and the company was going to offer its one-year 100,000-mile guarantee on
each and every one of them. So with all this being said with the money coming in, the contracts being
signed, why was this the time to go back to the 500? The point had been proven and the money was
being made. The Cummins boys, Klessy now in semi-retirement and his engineer brother Don who
was running the operational side of the company were racers and racers know how to read rules
and identify when they may have an advantage in them to work in their favor. For 1950 race
officials had announced that four-stroke diesel engines could measure 402.68 cubic inches and
two-strokes 274.59. This contrast to spark ignition engines which were limited to 4.5
liters naturally aspirated and 180 cubic inches or three liters supercharged.
Diesels could be supercharged with no displacement penalty. Cummins management gathered and discussed
the issue and they decided to go racing again for a few practical reasons. A, it was company tradition,
B, they were a pioneering force in high-speed diesels and wanted to keep that position in
the public eye and a race engine could certainly help that and C, the race brought incalculable
and invaluable publicity that could not be bought otherwise. Engineers were consulted to see if they
believed the JBS could be made into a powerful racing engine. They told the managers that a JBS
engine had been power pulled to 170 horsepower on the dyno before it kind of ran out of supercharger
the day before and that given the chance to use the much larger blowers off of the 275 and 300
horsepower NH engines they could likely make way more power than that. They also mentioned that they
had experimented with a four-valve cylinder head after the war and they still had those heads
guaranteeing massive power gains. The testimony so to speak from the engineers was all management
needed to hear and on the day before Christmas in 1949 the edict came down. Make the JBS as powerful
and high revving as you can, spare no expense, test every idea and have it ready by May.
Not only would they but this would become in my opinion one of the coolest high-performance diesel
engines ever made no matter the year or the decade. Immediately there were theories and
questions and goals. The theory was that they need to make at least 127 miles per hour to qualify
for the 8500 as they looked at the speed charts over the last couple of years. They'd need an
engine that could live at 4000 rpm absolutely unheard of for a diesel at this time. It needed to
be made of aluminum also unheard of for diesels at this time. Power would need to be somewhere around
330 horsepower and the BMW P would need to be around 168 a quantum leap from the factory number
of 152. The questions, can the fuel injection requirements for volume be met? Can fuel injection
even work at that high an rpm? Does 4000 rpm allow enough burn cycle time in the cylinder to
actually make power? Would normal diesel fuel and oil work? Can a high load engine like this
actually be made of aluminum? And could they actually reduce the weight of the production engine
by over 600 pounds? Their job was to find the answer yes to all these questions so
off to work they went. A few things went in their favor very quickly. The connecting rods,
beefy as they were, were strong enough to live at 5400 rpm according to the math. The valve train,
meaning the parts and pieces were capable of living at 4000 rpm. After that all bets were kind of off.
In January of 1950 a JBS 600 was placed on the dyno. The old experimental four valve head was
taken out and dusted off and bolted on. The engine was pulled to 4000 rpm basically to see what would
happen. With guys likely hiding under their desks it got there and lived for 90 seconds. The bottom
end burned up. Experimenting with different bearings got them the same result which was
dead engines. But they were learning. In order to fix the oiling issues the main bearings and
the rod bearings were grooved in the center to provide a larger cushion of oil. SAE 10 was
determined to be the weight of oil they needed and used and used all the way through. An auxiliary
motor driven oil pump was added. That additional pump brought the volume of oil up to 30 gallons per
minute and kept the engine at 50 psi at full song. The supercharger being spun off a belt drive on
the front of the crank was killing the front main bearing so it was ditched for one that would be
mounted like the 1934 cars laying down in front of the engine and driven right off the snout of
the crankshaft. A small viscous type dampener is used to stop vibration at the end of the crank.
So the next issue was with pistons. The wrist pins were splitting at high rpm operation. Sometimes
the pins would break the pistons and sometimes the pins would break the rods but ultimately they
were breaking stuff. The fix here was relatively easy. They went to a thicker wall wrist pin and
it did add some rotating weight to the engine but they had no choice. The pistons themselves
started with three 532 inch rings and were eventually redesigned with an eighth inch ring
package. Piston clearance which was 55 10 thousands and a stock engine was modified to 95 10 thousands
for this unit. With the addition of more load and more heat from combustion and more complete
combustion the pistons were expanding more than they would in a factory application which is why
they opened these up a little bit in terms of the gaps. The four valve cross flow cylinder head is
kind of a story on its own. No production Cummins at this time or ever had used a cross flow head.
Various shapes and sizes of combustion chamber were experimented with and the engineers admitted
this was done by trial and error method. The amazing pickup of 40 horsepower right off the jump
when going from the two valve to the four valve head was encouraging but they needed way more.
Ultimately a wide flat chamber was chosen and a piston with a slight dome was used. The chamber had
no swirl and almost no squish. The more they went this way the more power they made despite the
commonly accepted need for lots of both squish and swirl they had none and they got faster
and more powerful the less they had. Now factory Cummins injectors were used in modified form.
The injector pump cam was reworked. The injectors themselves had more lift and a higher rate than
stock as well as in large spray holes. Shockingly the injection timing was exactly what it would be
in a lower speed stock application. They tested injection timing 10 degrees slow 12 degrees fast
and they ended up right back where the stock timing would land in a normal engine you'd find in a dump
truck. Pistons running into valves was an issue to start with mostly because of valve float. This
was cured with camshaft design as well as improved valve springs. One of the neatest things I learned
in researching this video was that the company used high speed cameras remember this is in 1949,
1950 they used high speed cameras that shot at 3000 frames per second to monitor and review
valve train function. Yeah a compression ratio of 14.25 to 1 was settled upon and it generated
1700 psi of cylinder pressure. Fuels from kerosene to heavy oils all the way to number four fuel oil
were tested but regular diesel worked the best. As mentioned this was going to be an all aluminum
engine but I've not mentioned anything about that during testing yet and there's a good reason.
It didn't exist yet. All these tests are being run on an iron engine because the guys in the
pattern making department were busy modifying their stuff for aluminum parts which included the block,
cylinder head, main caps, pumps, pipes, covers and brackets. When all those parts were completed and
the aluminum engine hit the dyno there were some interesting findings. For starters things like
bearing clearance is loosened up. The pushrod clearance has changed so much with temperature
that the engine had to be started with everything loosened up and then adjusted when it was at
temperature. Now the biggest offender here they had steel pushrods in the engine and those pushrods
were expanding at a different rate than the block and cylinder head. The fix though was
simple. They went to aluminum pushrods. The next fix was a little more challenging. Power was down
by 10% and this was finally discovered to be the propensity that aluminum had to dissipate combustion
heat a lot faster than iron. Where cast iron would get hot and stay that way aluminum shed heat
very quickly. Design changes in the cylinder head which were unspecified in any research I've done
regained in the lost power. Durability was the next thing to test and test that they did.
They ran a simulation of speedway laps on the dyno. 10 seconds at full throttle, 20 seconds
deceleration and they did this for six hours at a time and the engine passed with flying colors.
As a reminder the crank, rods, bearings, cylinder liners, injectors and pistons with
mild changes were all factory parts. The Rootsblower making 14.7 pounds of boost was also a factory
piece off of an NH Cummins series engine. So for their goals where did they end up?
345 horsepower at 4000 rpm and an engine weight of 840 pounds. Now just a minute ago we were
talking about a 1500 pound production engine that made 150 horsepower making 1 horsepower for every
10 pounds it was lugging around. This engine was down to 840 pounds and that number went
to 2.47 pounds for every horsepower which is incredible. The targets for BMEP or brake mean
effective pressure were blown out of the water. 168 was the goal, they went to 172 at 4000 rpm
and 188 at peak torque well exceeding what they were originally set out to do. One of the other
things they exceeded and really didn't know they were looking for in the first place was a look at
the frictional losses the engine suffered when it went over 4000 rpm. When they went to 4300 rpm
the engine only picked up an additional 8 horsepower so you can tell that 4000 rpm was the sweet spot
anything after that you were wasting your time and this engine was also below or limited as the
Roots was doing all it could to efficiently feed the engine at 4000 rpm. They had shaved all that
weight, they had kept the strength, they had taken a 150 horsepower engine that spun to 2500 rpm
and made it a 343 horsepower engine that spun to 4000 rpm and they did it all in 1950 by hand with
their brains and slide rules and it's super impressive. The engine had 70 hours of dyno
testing when it was pulled off to be mounted in a new race car. Before we get to the car in the
Indy 500 of 1950 we have to recognize the successes the Cummins managed here were significant. This
was not just some whimsical racing program this was all applied stuff that would aid them in the
future. For starters the J series of engines benefited from this research immensely to
understand how hard they could be pushed and where inherent gains could be made. They doubled and
then some the output of a truck engine in four months reduced its weight by 45% and kept reliability
in an insanely harsh environment. They learned that standard oils and fuels could work in
extreme environments and they had come to learn that they had basically found the sweet spot for
injection timing no matter what the river range was. They also now knew that supercharging and
rpm were where all future development work should be concerned for future families of engines.
Perhaps most importantly and most clandestine there was secret technology on this engine that
Clussie Cummins had been working on. It was in its infancy but it was used on this engine for the
first time and this technology when refined would help Cummins dominate in the diesel marketplace
for decades and decades to come. It was called the pressure time fuel system and it made its
debut on this car at the 8500 but no one unless you're a diesel mechanic had any clue that they
were looking at the breakthrough of the diesel century. This was a primitive by today's standard
kind of common rail system and I use that term loosely. This was fuel metering based on pressure,
time, principles. The injector interval determines the time for metering that the orifice of the
injector stays open. This is controlled by the engine speed and the rate of the camshaft rotation
as well as the plunger in the injector's movement. Fuel pressure is generated by a gear driven
positive pressure pump. The fuel pump turns at engine speed and low pressure lines serve all
the injectors so they're getting equal volume and flow. The benefit to this system is that the
injector itself does all the metering and injecting work in one. This allows for massive pressure
on the order of 20,000 psi at the injection point which makes for an amazingly fine atomized mist of
fuel. No other system at this time was delivering this precision of injector timing and pressure.
This allowed for far better combustion, economy and it spelled the end of the troublesome
distyle pumps that were standard for this era. It was such a company secret because no one else
was even close on this tech and it would not actually carry a patent until 1954. This most
advanced diesel engine in the world was to be backed by a single plate Auburn clutch in a three
speed Cadillac transmission which had been modified with a Buick tail housing that also
utilized a Buick Torque Tube ball universal joint and driveshaft. A conzi quick change axle was to
catch all this power headed backward and Goodyear disc brakes. The first car at the Indy 500 with
disc brakes, a Cummins car, was this one. So what about the rest of the chassis? This arrived on
April 4th of 1950 straight from the legendary Curtis Craft shop of Frank Curtis in California.
It was a custom version of his 3000 series chassis that had the engine area lengthened by four inches
to allow the fitment of the still massive diesel. The wheelbase was 104 inches and it was not only
the first car at Indy with disc brakes, it was also the first with independent front suspension.
The rear was located with large hairpins on both sides. As advanced as it was, this thing was still
a tank as compared to the other roadsters at the race. A guy named Jimmy Jackson was tapped to drive
the car and at his request it was painted a bright green with a yellow 61 in the nose. He dubbed it
the green hornet. Without a doubt it was the most expensive car at the Indianapolis Motor Speedway
with a reported $50,000 price tag and that was likely low when you consider all the broken parts,
the R&D time, the overtime and more. The good news for the team is the fact that they would not have
to wait long to see their work in motion. On May 1st of 1950 the green hornet was the very first car
in the racetrack of the month and boy was it slow. For starters it was overheating, a new radiator
was designed and a scoop added to funnel air over the top of the engine and when those issues were
handled they got into it. The car was at first lapping at 120, then 124 and then 126 but the
field was at 130. This was not good. On the second to last weekend of qualifying it was only able to
muster 126 miles per hour again. Were they actually sunk with this new awesome piece? Almost. As these
guys were lapping the engineers were 45 miles down the road with a second aluminum engine doing
whatever they could to find more power on the dyno. After that engine got every tweak the
engineers could throw at it, it was rushed to the racetrack and installed in the car just in time
for final qualifying. And when final qualifying commenced Jackson began lapping at 128 miles per
hour but the team waved him off and he came in. They were close. The fresh engine had picked up
a few horsepower and that meant more speed. They made some chassis tweaks and sent Jackson back out
for his final attempt. He ripped off a first fast lap of 129.534 miles per hour and averaged 129.208
which placed him squarely on the bump spot. He was in but hardly safe. For an entire day they
watched car after car to try to bump them out of the field and they all failed. Even the novice.
So Jimmy Jackson was going to start the 1950 Indianapolis 500 from the back row.
The race began and it started slow as the team designed. They wanted to work up to an average
lap speed of 120 plus and as time went on they were doing just that and they were climbing 30th,
25th, 20th and then they were running 16th 130 miles into the race. It was at that moment
that Jackson heard a horrendous noise and quickly pitted. That old adage about green race cars being
bad luck? Yeah, here we go again. The flange holding the crank dampener had failed and when
that thing cut loose it played hell with the blower drive which remember was on the front
of the engine as well because the roots blower was hung out there like a potman style setup.
Their race was over. The damner had torn up too much stuff in the front of the engine.
However, the green hornet was not done because Bonneville was calling. On September 11th 1950
Jackson and the green hornet rewrote the diesel speed record books again. They went 163.82 over
147 over 10 kilometers and 148.14 over 10 miles. All those marks were new world records and the
records they took that day those are the ones that were set by Bill Cummings on the Daytona Sands in
1935 so in the end it was a green hornet just one that was better suited going straight than turning
left. 1952 would be the year that most people know about but the details are so rarely shared
in the short incomplete histories you've seen I'm here to fill them in. That's what I'm here for
so let's do it. As it was their want and their practice the engineers at Cummings once again
led by Don Cummings reconvened and analyzed the 1950 performance in 1951.
Cummings brought in Nev Reiners, Thane Hauser, Bill Dope, Mike Fellows, Art Echelman and Joe
Miller as his Skunk Works team. Their goal was simple, more power, less weight, a better car
and better results. Among them one of the guys had a brilliant concept. Because their engines
were so heavy and you know even when they were light they were heavy they needed to do something
about the center of gravity in these cars to aid handling. It just so happened that the company
had a series of engines known as the NHH. This was a standard NH series Cummings engine but the
second H stood for horizontal. It was designed for being mounted under the floors of buses
effectively laying on its side. They could apply all they had learned making that series of engines
to the already pretty racy JBS600 platform they had run in 1950. Laying the engine over almost
flat would make the car far lower, the aerodynamics far better and the center of gravity perhaps the
lowest in Indy 500 history. They all agreed to pursue this course of action. Cummings also had
another idea they were playing with in-house at this time, turbo charging. Recognizing the
limitations of root supercharging, the experiments with turbos were a way forward for the company.
A turbocharger could compensate for altitude which roots blowers could not. Their use of engine heat
to make power rather than robbing it from the crankshaft and many other ideas make them an
attractive solution, an attractive replacement for a roots blower. The problem was the turbo
chargers in 1951, they weren't that great. Not that great at all. The turbo struggled big time
matching the low end power of root superchargers and they made a lot of smoke as the company was
trying to get this new fangled fuel metering correct with a different power adder. They also
lacked throttle response and ironically to what we know about turbochargers in today's world,
they had horribly sluggish acceleration. Now these turbos are also limited by exhaust temperatures
because of metallurgy and turbine speed because of the same reason. On the positive they made
measurably more power than superchargers at virtually any rpm over 2000 and did it with
the same fuel consumption numbers. The company even experimented with roots and turbo charge compound
systems in the 50s to try anything they could to reduce lag and make more power. A couple of things
buoyed the engineers on the race program with turbochargers though. A 200 horsepower NH6 engine
when turbocharged made 262 horsepower with no internal changes, a 31% increase in power.
An NT engine that made 262 horsepower as it was produced would make 335 horsepower on the dyno
with a turbo a 67.5% increase in power. And frankly the engineers thought they didn't need a car
that could pull away from stop lights. They just needed one that could run at high rpm for hours
and outmuscle the competition. So they all agreed to pursue a turbocharged path. It would be the
first turbocharged car in Indy 500 history. The JBS 600 from 1950 became the JT 600 for 1952. The
T obviously standing for turbocharged for those of you super slews out there who didn't understand.
The engine used dry sump oiling. Magnesium replaced aluminum parts to save weight whenever
possible. Using a 4.125 inch bore which is 105 millimeters and a 5 inch or 127 millimeter stroke,
the engine was laid over on its side 85 degrees. The Schweitzer Cummins turbocharger fed by a pair
of split manifolds provided 20 psi of boost and the still relatively secret PT fuel system that
pressure time fuel system fed the whole thing. With very few to the point of being basically
inconsequential internal changes and tweaks other than dialing in the fuel system, the engine made
380 horsepower at 4000 rpm and 430 horsepower at 4500 rpm. A massive leap of 100 horsepower from
the last race and more importantly in an era when 3 liter often houses are making 340 horsepower,
these guys finally had an advantage that could be applied to win the race. The engine which sounds
comical to celebrate weighed 750 pounds now down another 100 from the last one and down from its
1,545 pound factory weight so yes they were now less than half the factory production weight.
Frank Curtis was once again called to build them a custom car, one that would change not only
Curtis's business but the entire look of the Indy 500 for the better part of a decade. The
chassis used was very similar to the suspension of the 1950 car with independent front suspension,
radius rise locating the rear axle and torsion bars at all four corners. The car had a 103 inch
wheelbase and a track width of 56 inches and 58 inches. It was roughly half a foot wider than
anything else on the track but it was also lower, way lower. In order to get the car dimensionally
correct, Cummins actually sent a wooden mock-up of the engine, one-to-one scale, out to Curtis so
they could kind of build the car around it. Flown by airmail to California it was exactly what the
metal crafters needed. When they were done they had created the most advanced Indy car anybody
had ever built. A 23 inch cowl height was preposterous. The driver Fredy Agabashian sat four inches off
the asphalt in a cockpit that was slightly offset to the right. The drive line was offset from the
centerline of the car by eight and a quarter inches and it ran down the left side shifting 150 pounds
of transmission, driveshaft and other accoutrements to the side of the car you wanted it on in order
to turn left. This version of the Cummins engine special had the lowest center of gravity in Indy
500 history, enrolled on huge 18 inch wire wheels and those wire wheels were wrapped in
reasonably tall tires, kind of giving the impression that the car could be run upside down without the
headrest portion of the body. This was all awesome but the Cummins engine special still
tipped the scales at 3,100 pounds. That was still about a half ton over what even the most robustly
built roadsters were carrying with them at the time. The car went from Los Angeles and Curtis's
shop when it was done to a place no other Indy car had ever been, a wind tunnel. This particular one
happened to be at the University of Kansas Wichita. In that wind tunnel they worked on windscreen
designs and studied the overall aerodynamics of the car. It was a first and they learned plenty.
The car was actually tested in November of 1951 at the Speedway but was run in a very,
very conservative fashion because they figured if they tipped their hands the car could actually
be banned by race officials. As it turned out this was the smartest thing they could have done.
Come the month of May 1952 the Cummins team was ready with the best engine,
the best racer and the best race driver they had ever had. They played their cards close to the
vest and then pole day came. Agabashian had made some earlier attempts but strategically
the team waited to pounce. With 15 minutes left on the pole day clock the car left the pits and
entered the racetrack. Agabashian put all 400 plus horses to work and the car ran up to speed as
quickly as possible. As he came around to take the green flag the odd sound of the lower revving
diesel might have fooled some people but the Cummins boys knew that he was on one.
The first lap was an Indy 500 track record 139.104 miles per hour but the heavy car was
destroying tires as fast as Freddy could drive. Successively over the next three laps he kept
losing just a little speed and on the fourth one with one tire worn almost all the way to the
chords he crossed the finish line with an average speed of 138.010 miles per hour.
Freddy Agabashian had just set the single lap record at the Indy 500 and the qualifying record
in the same rip and the Cummins diesel would be on the pole 41 years after Klessy help wrench
Ray Haroon to a win. The even better news for the team is the fact that qualifying and racing
were two different things. Nobody could push their stuff as hard in the race as they did in
qualifying the tactics were different and there would be an ability to save tires and kind of
extend their life. If Agabashian tried to drive every lap like he drove those four the team would
be out of tires 20 laps into the race. But with stuff like traffic and caution flags and other
things that'll happen during the race there was definitely plenty of time and plenty of ability
to stretch the tire life. They knew they wouldn't have any problems with fuel but if Freddy could
stay clean out there and keep the tires maintained these guys had a fighting chance to win the race.
Not everybody was happy about that. Usak who ran the race was among that group. Remember
the Cummins engineers concerns about acceleration and turbos? They were warranted as it turned out
even at speed because the turbos weren't a lot of help in the get up and go department even when
the car was rolling. Lag was incredible and this was about to be a big problem. When the Pace car
pulled off and Fred Agabashian came around turn three at the Indy 500 looking for a green flag
he should have already been on the gas but he wasn't and that laggy turbo sunk him. He entered
the first turn eighth ended the first lap ninth and he started on the pole. Driving out of the
corners the car just took too long to react but all hope wasn't lost as the laps clicked off
Agabashian settled in learned the car and began to steadily regain position moving his way all
the way back to fifth. Averaging 131.5 miles per hour to the leader's 130.843 Agabashian wasn't just
hanging in there he was making time and reeling in the leaders of the race. There was plenty of
time left to go as well. Suddenly on lap 71 the car began to drastically lose power and he pulled
into the pits. Achilles had his heel and the Cummins special had its air scoop. There was a
metal air horn that sat directly next to the radiator to move air to the turbocharger which
was mounted ahead of the engine. The issue at the time was that scoop wasn't just moving air it was
moving stones and rubber and whatever other junk was on the racetrack into the turbocharger eventually
that built up and killed the turbo and once that happened game over. They would go into the history
books as the 28th finisher after running top five and gaining on the leaders. The craziest part about
this is a simple screen might have actually saved the bacon of this team but it just wasn't in the
cards. If there was a silver lining they definitely had a car that could compete and there would be
more power found and more weight saved for 1953 but that date would never actually come. USAC wasted
no time and acted swiftly after the race. These guys didn't need diesels qualifying number one or
anything at the front of the field. So they declared the maximum displacement for diesel
engines in 1953 would be 335 cubic inches destroying any chance these guys had to compete.
There was no engineering value to the company to make a clean sheet engine with no application
even if they did the diesel of 335 cubic inches in this time period would not be making near
competitive power to overcome things like its own weight. Wilbur Shaw who was running the race at
the time said quote it had so much power we will unquestionably reduce the displacement advantage
end quote. That so-called advantage was what allowed the car to be competitive. The combination of
Shaw's words and then the reinforcement of those words by writing it into the rulebook
ended Cummins racing days at the Indy 500 done in by the stroke of a pen.
Interestingly when the car was restored in 1968 though it was discovered that the
crankshaft had a massive crack in it and was destined to split in two at any moment. The
turbo may have been the official cause of the car's demise but there was another bigger problem
waiting to happen there. All five of the Cummins race cars still exist and they all run. It's a
company that values its history and I think that rules. So let's review. First diesel to ever compete
in the Indy 500. First and only car to run the whole Indy 500 without stopping. First car with
disc brakes. First car with independent front suspension. First car with a lay down engine
and offset driveline. First car with a turbo charger. First and only diesel to ever qualify in
the pole. Only two stroke engine to ever finish the race. The first car to use the wind tunnel
in its design. The highest fuel economy ever recorded in Indy 500 history. Tell me why Cummins
is not the most innovative company in the history of the Indy 500. Do it in the comments. I'll check
them. That's the story of Cummins diesel at the Indy 500 in depth as you've never heard it.
The 1952 running was the icing on a cake 41 years in the baking. Five cars, five engines,
endless innovations and the use of racing to advance the cause of diesel engines in ways no
one had ever considered before. Cummins would not have done what it did in the industry in this
era without racing. It drove the engineering and translated back to the product. It's in my mind
the best part of the story. Clessy Cummins engines never made it into luxury cars but if he had lived
long enough to see Dodge plunk them into pickup trucks starting in 1989 I sure bet there would be
happy tears rolling down the man's cheeks. Something you may have known a little about
now you know a lot about and like I always say knowledge is horsepower.
I'm Brian Lones. Thanks for watching. Score a t-shirt in the store to support the channel. See you next time.
About this episode
Cummins’ diesel racing story at the Indy 500 unfolds like an engineering campaign: from early fuel metering and direct injection breakthroughs to a 1952 turbocharged “Cummins special” built around tight rules and high-rpm targets. The hosts connect ram-air smoke reduction, unusual 2000 rpm diesel revs, and dyno durability testing to real race outcomes—then show how rulemakers responded with displacement caps. Along the way, the episode ties publicity stunts, trucking success, and repeated hardware failures into one long, improbable arc.
Cummins diesel engines are an American institution.
They've been one of the most massive manufacturers of diesel engines in the United States for more than 100 year now, but did you that they have an incredible history in racing, tied to the Indy 500.
From 1931-1952 Cummins ran five different cars with five different engines at the 500 and all of them are amazing. Cummins is credited for more Indy 500 firsts than any other single person or entity in the history of the race. This is the complete history of Cummins at the Indy 500.
Their most massive and well known headline was winning the pole in 1952 but that was a moment 40 years in the making. In this video you'll learn about the cars, the people, and take a deep technical dive into the engines that defined these events and Cummins as a company. These were production diesel engines mixing it up with racing engines on equal footing.
It's one of the most surprisingly cool racing stories in American motorsports history.
