Cylinders are the engine’s chambers where the fuel burns. The idea described here is to interfere with that burning so the engine won’t keep driving the vehicle.
They’re trying to make the engine struggle to keep running (“choke”), so it loses power. With less power, the engine can also slow the truck down (“drag”).
A pit stop is when a race car pulls into the pits for service. Not having one means the car could go the whole race distance without needing fuel or tire changes.
Concept
Memorial Day weekend
Memorial Day weekend is a U.S. holiday time. The hosts mention it to explain when this early Indy 500 event happened.
The Indianapolis Motor Speedway is the track in Indianapolis where the Indy 500 race happens. The hosts are saying the track was brand new when the first Indy 500 was held.
Car
Packard limousine
A Packard limousine is a big, fancy car. In the story, they put a different engine into it, and that’s what makes it stand out at the auto show.
The Tesla Model S is an electric car, meaning it runs on electricity instead of gasoline. In the podcast, it’s mentioned as a recognizable car name while they talk about engines and power setups. The point is to help you follow the comparison they’re making.
Car
Cummins Model U marine diesel
The Cummins Model U is a diesel engine that was made for boats. Here, they put it into a car to try to set a land-speed record.
The Indianapolis 500 is a famous big race in the U.S. The hosts are talking about it because the rules decide whether certain cars—like diesel-powered ones—can even qualify.
“Diesels” are cars powered by diesel engines. They work differently than gasoline engines, and in this segment the race rules decide whether diesel cars are allowed.
To “qualify” means you have to meet the race’s entry rules before you can start. Here, the diesel car has to hit at least 80 mph in qualifying to be allowed in.
Car
Cummins diesel special
This is a race car built around a Cummins diesel engine. The hosts talk about it like a specific entry in the race, including how heavy it is and whether it even qualifies under the rules.
“Board track era” means a time when race tracks were made of wooden planks. Racing on them was intense and risky, and it influenced how drivers and cars handled the track.
Some bolts are designed to be stretched when you tighten them. If the instructions say they’re one-time use, reusing them can mean they don’t clamp tightly enough.
A gasket is a thin seal that helps stop leaks between two parts. It often needs replacing when you take things apart.
Car
Surpass AS01
Surpass AS01 is a specific tire model. The point they’re making is that it’s meant to feel grippy like a sporty tire, but still be practical and dependable when conditions aren’t perfect.
A performance tire is a tire designed to grip the road better and help the car handle more sharply. It’s usually made with rubber and tread patterns meant for better traction than regular tires.
This is a promise from the tire maker that the tire is covered for a certain number of miles. If something goes wrong within that mileage, you may be able to get a replacement.
Pothole protection means the tire is designed to better handle hitting rough road bumps and holes. The goal is to reduce the chance of getting damaged or punctured.
Tire replacement is when you stop and put on new tires. In racing or rallying, it’s done when the tires wear out or get damaged so the car can keep handling safely.
Caterpillar is a company that makes heavy machines and diesel-powered equipment. The episode is grouping it with other big diesel players in heavy-duty work.
A “rebuild” is when a mechanic takes the engine apart and fixes/replace worn parts. The claim here is that diesel engines usually need that less often than gasoline engines.
An “over-the-road tractor” is the main truck used for long-distance hauling, pulling a trailer. The episode is saying that by the mid-1950s, most of these long-haul trucks ran on diesel.
Car
Cummins NH series
Cummins NH series is a type of diesel engine that powered older heavy trucks. The point here is that it’s loud and rough compared with modern truck engines.
This describes an older diesel engine that doesn’t spin very fast, but makes strong pulling power. The “cast iron” part means it’s built heavy and sturdy, which often makes it sound and feel rougher than modern engines.
Cubic inches tell you how big an engine is internally—how much space the pistons move through. Bigger displacement often helps an engine make strong low-end pulling power.
“Inline six” means the engine has six cylinders lined up in a row. That design can help the engine run smoothly and make good pulling power at lower speeds.
RPM is how fast the engine is spinning. The point here is that this diesel makes strong pulling power at relatively low RPM, so it feels strong without needing to rev it out.
They’re talking about how the car gets fuel to run. Here it’s all mechanical, so there’s no computer controlling it—just parts that move and push fuel.
The Volkswagen Beetle is a small car made by Volkswagen with a very recognizable, rounded shape. In the podcast, it’s mentioned because it’s a familiar reference for how much something weighs. They’re basically saying the engine block is heavier than the whole car.
A “gearbox” is the part of the truck that changes gears. It helps the engine spin at the right speed for what the truck is doing—like pulling uphill or slowing down.
A “twin stick” is a truck shifter with two levers instead of one. It helps the driver pick different gear ranges, which can make it easier to control the truck—especially on hills.
Air brakes are truck brakes that use compressed air to squeeze the brake components. They’re common on big vehicles because they can generate a lot of stopping power reliably.
A 6% grade is a way of measuring how steep a hill is. The steeper the hill, the harder it is to control your speed, and the more your brakes have to work.
Kinetic energy is the energy a moving vehicle has due to its motion. On a downhill, a heavy vehicle’s kinetic energy must be turned into heat by the brakes (or controlled by engine braking), which is why long grades can overheat brakes.
Brake fade is when your brakes get too hot and stop working as well. On a long hill, you might notice the brake pedal feels weak or changes, and you can’t count on the brakes to slow you the same way.
A runaway ramp is a safety escape area on steep roads. If your brakes stop working, you can steer onto the ramp so it helps slow the vehicle down safely.
“Gear it down low” means shifting to a lower gear before the hill. That helps slow the vehicle using the engine, so you rely less on the brakes heating up.
The camshaft is like the engine’s timing controller. As it spins, it pushes the valves open at the right times so the engine can breathe and make power.
On a camshaft, lobes are the bumps that control what gets pushed and when. A “third lobe” means there’s an additional timing feature beyond the usual ones.
The compression stroke is when the piston squeezes the contents in the cylinder. What happens during that squeeze—like valve timing—changes how the engine runs.
The exhaust valve is the valve that lets burned gases out of the cylinder. Opening it at the wrong (or unusual) time can change how the engine operates.
The idea is that the diesel stops making power the normal way and instead gets used to push air around. The engine’s effort turns into compressing air rather than driving the truck.
Jacobs Manufacturing is a company mentioned in the story. The hosts say it becomes involved because of a family connection and then sets up a new division to build the product.
A Jacobs Chuck is a type of drill holder—the part on a drill that grips the bit. The hosts are saying you may have seen the name on older drill equipment.
Engine braking is when you slow down by letting off the gas and using the engine to create resistance. On many gasoline cars, it feels stronger because the engine airflow gets restricted.
A throttle plate is a flap that controls how much air the engine gets. When it closes on a gasoline car, the engine has to work against that restriction, which helps slow the car down.
A runaway diesel is a dangerous condition where a diesel engine keeps running uncontrollably because it continues to receive fuel/combustion even when the driver cuts the normal fuel supply. The key idea here is that diesel engines can keep spinning on internal combustion characteristics when you lift off, so the engine isn’t “on your side.”
A “runaway truck” is when a truck starts speeding up on its own and won’t slow down the way it should. It’s usually because something in the engine control isn’t working right.
Term
head gas failed
They’re saying the engine’s control for how much fuel/air it gets failed. When that happens, the engine can start speeding up on its own.
The Porsche 911 is a sports car made by Porsche that’s known for strong performance. The podcast is talking about a problem where the engine didn’t behave normally and started running in an unexpected way. It’s used as a reference point for a serious mechanical situation.
Sometimes a runaway diesel happens because engine oil gets into the combustion. Since the engine is using its own oil as fuel, it can keep revving and speeding up even when you try to stop it.
“Floored” means the accelerator pedal was pushed all the way to the floor. They’re saying they already gave it full gas, but it still surged faster than before.
A diesel engine works by squeezing air very tightly, which makes it hot enough to ignite fuel when it’s injected. The key idea is that the engine’s work is tied to compression and combustion happening in a cycle.
Retarding force is what slows the truck down. It can come from the engine working against you, like when you downshift and the engine helps brake the car.
This is the idea that, during the piston’s motion, the engine can actually fight against the drivetrain. That resistance helps slow the truck down—like engine braking.
A blow-off valve releases extra pressurized air when you lift off the throttle. It helps protect the turbo and it’s also responsible for that loud “pssh” sound some turbo fans love.
Term
mountain pass
A mountain pass is a steep downhill road. Trucks often need extra help slowing down for long stretches so they don’t overheat the brakes.
The brake pedal is what you press to slow the car or truck. The speaker is saying that with the right downhill strategy, you may not need to press it much.
A jackknife is when a trailer swings around so the truck and trailer form a sharp angle. It’s dangerous and usually means the vehicle lost stable control.
Term
federal regulator
A federal regulator is a government agency that makes safety rules. The speaker is saying nobody required this device by law—drivers and the market chose it.
“Cab over” means the driver sits above the engine area, with the cab pushed forward. It often makes the truck shorter and easier to handle in tight spaces.
A Jake brake is a system that helps slow your truck using the engine. It’s useful on steep downhill grades because it can take some work off your regular brakes.
A rock crawler is an off-road vehicle made for rocky trails. “Articulating” means it can twist and flex so the wheels stay on the ground when the terrain is uneven.
An exhaust actuator is a moving part controlled by the truck that changes how the exhaust system behaves. For engine braking, it helps the engine create more slowing force.
A compression release engine brake slows the truck by changing how the engine compresses air. That makes the engine fight against rotation, helping you slow down without using the regular brakes as much.
An exhaust back pressure valve is a valve that partially restricts the exhaust. That restriction can make the engine harder to spin, which helps slow the truck.
A heavy-duty diesel is a big truck that runs on diesel fuel and is meant for hauling cargo. The episode is saying that, back then, these trucks needed extra help to slow down safely on steep downhill roads.
Cummins Incorporated is a company that makes diesel engines for trucks. Here, they’re mentioned because they bought the technology related to the Jake brake.
An exhaust brake is a system that makes the engine slow the car down by restricting the exhaust. It’s especially useful on long downhill stretches to reduce how much you use the regular brakes.
The exhaust manifold is the part that gathers exhaust gases coming out of the engine. It’s like a collector that funnels exhaust into the rest of the exhaust system.
A “Jake brake” is a diesel-truck feature that helps slow the truck using the engine. It makes a noticeable sound, and people often use that sound to tell whether the truck is using engine braking.
Engine braking means slowing down using the engine instead of pressing the brake pedal all the time. On many diesel trucks, it can also create a loud, recognizable sound.
LIVE
My head just failed and it just started running away at the intersection.
So I just, I, obviously you turn, I didn't know what it was happening.
I was like a teenager.
I'm like, what happened?
I didn't know that you just, you know, could get out and put your hand over the thing.
Like I had no idea what was going on.
I was driving on the freeway and it was like, and I'm like, whoa, you know,
cause I've already got this.
I already have it floored because it will go any faster.
And all of a sudden it's going faster than it's ever gone, but only for like a few seconds.
I'm like, well, that's weird.
How could I recreate that regularly?
Stoplight and it filled the whole intersection with smoke.
Fire department showed up.
Someone called the fire department.
Hey guys, welcome to overcrest.
I'm Chris and I'm Jake.
Hello, Jake.
How are you?
I'm good.
How are you?
What do we got going on?
I'm very good.
I want to talk a little bit about something that I've been wanting to
converse with you about for a long time.
It's a kind of a, a long meandering story with, with a point.
And I think you will also long for the ride.
And I'm hoping we can maybe change your mind on something.
Oh boy.
You have forever held a very close belief.
It's one of two things.
Okay.
What is it?
One of two things.
What, what two things?
It's most likely Mercedes, but it might just be diesels or it's Mercedes with diesels in it.
It is the summer of 1931, Jake and a heavy diesel truck is dropping down out of the
San Bernardino mountains on the old alignment of route 66 into the long,
steep gravel descent that everyone in the country calls Cajon Pass.
The kind of a descent that asks more of a truck than most trucks have.
The man at the wheel has been on the road for two weeks, 3,214 miles from New York to here.
All of it on a coast to coast speed record attempt for diesel trucks.
This was apparently before like the DOT regulations of how many hours you can buy in the
wheel as a commercial trucker.
Absolutely.
No regulations.
There's a no expressways, no Eisenhower.
This is 1931.
Yeah, okay.
All of this driving has been coast to coast on a speed record attempt for diesel trucks.
Three men are in the cab.
They've got bunks in the back and a stove and it costs them just $11 and 22 cents in
fuel for the entire trip.
That's funny to imagine.
Yeah, I'm curious what the like the conversion is for today's dollars or like, you know what I mean?
I'm sure it was much more relative either way.
That's amazing.
They're nearly at the end of the Cajon Pass when the brakes start to fade.
Then the brakes start to go.
He shouts at the man next to him to drop it a gear.
The man cuts the fuel and he works hard to pump with a hand pump to force water into the
engine's cylinders, hoping the engine will choke and drag.
Are we, are we going to get to any of the technical components here or also the fact
that he has another man he's shouting at to do things?
Yes.
Well, it's three dos in this truck.
It's three do cross country in this truck.
Just tell us slow down, slow down, hit the brakes.
There's no, okay.
This is just the passenger is telling him that.
Yes.
Yeah.
It's not like it's not like a boat where we have a wheel man and a throttle man or something.
Well, I mean, I guess it just depends on what you call your teammate when you're doing a cross
country run.
Yeah.
No, I just didn't know if like he was telling his other guy like, hey, downshift as he's
driving or something.
It's like, what?
Why is that guy downshifting?
Okay, I get it.
I get it.
Never mind is a runaway truck.
Yeah, 20,000 pounds of diesel and steel coming off a mountain.
Coming down to the bottom.
Do we know, do they have a load?
Oh, yeah.
Did we address that?
Okay.
Okay, we'll get there.
Okay, coming down towards the bottom.
He sees a freight train.
The caboose is moving slowly across the road in front of him.
He clears it by just inches.
He will carry the scars from that descent on his back for the rest of his life.
Emotional scars, Jake.
Emotional scars.
Yes, yeah, naturally.
Yeah, yeah.
The man at the wheel is Klessy Cummins.
The cargo in the trailer behind him is the number eight Cummins diesel special.
The first car in the history of the Indianapolis 500 to complete all 500 miles without a single pit stop.
Okay.
He is going home from that publicity tour and it just about killed him.
Yeah.
Oh, cool.
He climbs out of the truck, doesn't say much, but he makes himself a promise.
Rollback 20 years.
May 30th, 1911.
It's Memorial Day weekend.
The Indianapolis Motor Speedway is brand new, brand spanking new.
And it's hosting the first running of what will become the Indianapolis 500.
Ray Herron wins it in the Marmin Wasp.
Yes, the Marmin Wasp.
I feel like we've talked about that before.
Yeah, that rings the bell.
There's the first car to ever have like a roof in here.
Okay.
Yeah.
Inherence.
Did we see that one when we were in?
Do you remember we went to that museum?
Was that in Indianapolis?
Dude, they redid the museum.
I really would love to go to the museum.
They redid the...
I think we saw that.
I don't have to go.
Inherence Pitt working on the car as a self-taught young man from Columbus, Indiana.
He built his first steam engine at 11.
He is making suggestions to Herron's crew that nobody else is making.
Some of them work.
That kid's name is Klessy Cummins.
Eight years later, he starts his own engine company in Columbus with banker money.
Eight years later, he was old.
He was how old?
19 years old.
Yeah, he was 11 initially.
And then...
Yeah.
18 years old.
Company.
He builds diesels mostly for yachts.
Then the depression hits and the yacht business obviously disappears.
By 1920, he's looking for new customers and nobody believes diesel could power a passenger vehicle.
These must be all your ancestors.
Nor should it.
I agree.
Story done.
Great job, Chris.
Thanks for joining us on Overcrest.
He drops one of his engines into a Packard limousine
and drives it from Indianapolis to the New York auto show on just $1.39.
The auto show will not let him present because he forgot to rest.
So he rents a space across the street.
The $1.39 Packard becomes the talk of the show.
That's cool.
It's now February, 1931.
Look at that thing.
What a...
Yeah.
It's just...
Look at the steel wheels on it too.
I was going to say that thing's...
That's a beastly looking vehicle.
It is now February, 1931.
He commissions Augie Dusenberg to modify a model HS
and drops in a Cummins Model U marine diesel.
The engine has four cylinders, 361 cubic inches,
after he sleeves it down to fit the displacement rules,
and 85 horsepower.
It is a truck engine and a race car body.
He drives it down to Daytona Beach.
Himself and sets the diesel land speed record at 100.755 miles an hour.
It is the first diesel anything to crack 100.
Then he walks into Eddie Rickenbacker's office.
You know who Eddie Rickenbacker is?
A name rings a bell, but no.
Yeah.
Rickenbacker owns the Indianapolis Motor Speedway,
having bought it in 1927.
He also, at this moment, in 1931,
is the most decorated combat pilot in American history,
which is how you know him.
He has 26 confirmed aerial kills over Germany in 1918,
and a Medal of Honor on his wall pinned there by Herbert Hoover.
He's America's ace of aces.
The Speedway.
This is World War I.
World War I.
That's right.
That's right.
Yeah.
He's America's ace of aces.
That was just a different time for flying, I think.
Yeah.
Everything was much slower, obviously.
You know, it's slow motion dancing with guns.
Pretty crazy stuff.
100%.
Yeah.
I think we've done some stuff out of fighting in the past.
We have, but yeah.
World War I air warfare is very interesting and fascinating,
like you said.
I think dancing in the air with guns is a very good descriptor.
Rickenbacker is America's ace of aces,
and the Speedway is his second act.
This is the man Klessy has come to ask for a favor.
It is the so-called junk formula era at Indy.
The Depression had gutted the factory teams.
So they had relaxed the rules just to get cars on the grid.
New rules said in bigger displacement, stock blocks, no problem.
And you had to have a riding mechanic in the car again.
The serious factory money had all fled.
So basically they're just like, hey, bring what you want.
Let's just get people there.
Run what you brung.
Yeah.
Yeah.
So this was named by purists that hated the loosening of this.
Sure.
Okay.
Got it.
Cummins season opening.
He wants the diesel in the Indianapolis 500.
Diesels are not allowed.
Diesels have never been against them.
Rickenbacker thinks about it.
He just needs cars by diesel can race,
but it has to qualify above 80 miles an hour,
and it is not eligible for any prize money,
which kind of makes you go, did he actually think it could win?
Right.
That's interesting.
That's interesting.
Well, it's fuel economy, man.
The car is the number eight Cummins diesel special.
It weighs 3,389 pounds, the second heaviest in the field.
Only the second heaviest though.
Dave Evans is driving.
He's 30 years old from Evansville, Indiana.
Dave Evans from Evansville.
A veteran of Duesenberg's brutal board track era,
which is this, like this time where they used to race the,
like on wooden planks, literally ovals.
Burk the murder drone is the Nick.
Well, that's, that's more the motorcycle.
Yeah.
You know, same, same silo drone, I guess is what that's called,
where they run up the silo.
This man will never drive a car faster than this slow diesel.
Thane Hauser, his longtime partner is the riding mechanic.
He's the crew member giving hand signals from the pit wall.
I'm sorry.
The crew member giving hand signals from the pit wall
is Jimmy Doolittle.
Yes, that Doolittle Doolittle.
Okay.
He's just 11 years out from the bombing run over Tokyo
that made him a household name.
Guys, there's so many tangents here.
There's so many tangents and different things
that you could talk about.
We're not getting into Doolittle.
We should get into like the flying aces of,
of the, of World War One and all that, all that kind of stuff.
Is that Doolittle related in any way to the World War Two
Doolittle raids on Japan?
Do you know what I'm talking about?
That's it.
We're not going down the tangent.
Maybe.
Okay.
There's, I wonder if Doolittle is like a very like,
if there's a whole lineage there.
There might be.
The race goes on.
The comments is slow, but it's something else, man.
It doesn't stop.
Five hours, 48 minutes, 500 miles, not a single pit stop.
No tires, no fuel.
It just goes.
It finishes 13th, but it is the first car in the history
of the Indianapolis 500 to complete all 500 miles
with no pit stops.
It burns 31 gallons of furnace oil at a cost of a dollar 40.
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Okay, I have a couple of questions you probably don't
have the answers to but we can guess.
So he finishes 13th.
Do we know how big the field was?
I do not.
That wasn't, it wasn't dead last but you know,
was that mid-pack and then also you said no top stops
for tires either.
Was that necessary or like was that standard at the time
to replace tires as well as fuel stops?
Yes, you would replace tires if you needed to.
There was 30 cars, a little over 30 cars.
Okay, okay, yeah, that's a mid-pack, that's pretty good.
I don't think you're in the money at 13th place.
You what?
You're not in the money at 13th place.
No, no, but okay, interesting.
The race ends.
Still clearly it did not do as well as a gasoline-powered car
though Chris.
So like again, you're not making a good point here.
Well, it made it, it did better than 20 other gasoline-powered cars.
Yeah, but not as good as 12 others.
The race ends.
Ends.
Cummins does not put the car in a museum.
Instead, he puts it on a truck.
The truck is in Indiana, built in Marion, Indiana.
The truck is, wow, I typed Ann instead of Ann.
I'm sorry guys, I'm a writer.
That's, you know what I mean?
That's, no, it's all right.
The truck is built in Marion, Indiana
with one of Klessy's own engines under the hood.
Three men are in the cab with the bunks in the back, the stove.
Got it, yeah.
Number eight in a trailer, New York to Los Angeles.
Let's continue to show America what diesels can do.
Remember, Klessy's at the wheel with Ford Moyer also at the wheel
is test driver, riding along shotgun.
The third man, Dave Evans, three months out from finishing 13th
in a slow car that did not stop.
That is the cargo on the runaway.
That is the cargo being hauled by this crew.
All right, come back with me to Cohen Pass, summer of 1931.
The truck is at the bottom of that grade pulled to the shoulder.
The brakes are still smoking.
The freight train has rolled east.
The caboose he nearly hit is long out of sight.
The number eight sits intact in the trailer.
The three men are standing in the dust by the side of the road.
Klessy does not say much.
As we know, he made a promise.
That promise took 24 years to keep.
While he was working, the world changed under him.
By 1955, trucking is a different animal than it was in 31 when they almost ran into a caboose.
The diesel at this time and by this time had won.
Cummins and Detroit diesel and Mack and Caterpillar
carved up the heavy duty market between them.
And the gasoline truck started its slow walk to the boneyard.
Diesel is more efficient, pulls more weight, runs longer between rebuilds.
By 1955, most over-the-road tractors burn oil, not gas.
Forget what you know about modern trucking.
Erase the pilot travel centers and fleet lorogos and the GPS.
This is my big tangent.
I just want to talk about it.
Yeah, what does the landscape look like?
That makes sense.
Yeah, yeah.
Put yourself in a cab in 1955, Jake.
Close your eyes.
Put yourself in a cab.
I have a look.
Okay.
You're sitting on a vinyl bench seat six feet off the ground.
Behind you is either a cramped bunk or no bunk at all.
Right.
In front of you is a wheel the size of a manhole cover.
Beside your right knee is the engine, pretty much.
Probably a Cummins NH series, maybe a Detroit diesel 671, maybe a Mack.
Whatever it is, it's screaming at you from the moment you start the day to the moment.
You shut it off.
They're not quiet.
They're not quiet and they're not cool.
They're just let us talk first like just about this engine.
It's a slow revving cast iron beast.
The Cummins is the Cummins.
Yeah.
The NH series in line six is around 743 cubic inches.
We're going to do a best six cylinder engines of all time episode.
This one's going to be on there whether you like it or not.
This thing is about twice the original Cummins.
Like why this one?
Because it was legendary.
It's not necessarily always about performance.
It's about okay.
But like this if you're talking, if you say what is the most prolific Cummins engine of all time?
Everyone's going to say 6BT every single time.
Of course.
Why don't we include that one as well?
Like why not both?
Fine.
The Cummins NH series is around 743 cubic inches.
Twice the displacement of a modern American V8 and a much taller, much heavier block.
It makes maybe 220 horsepower by the early 60s.
They bolted on a turbocharger and I got it up to 300 and eventually 350 horsepower.
But horsepower is not what is working for you.
It is torque.
That's right.
And it sits in a fat band from around around 1100 to 1500 RPM.
You didn't rev diesels.
You don't have to.
You just sit on them and they just pull you along.
The fuel system is entirely mechanical.
There's a governor, a pump, injectors and linkages.
That's it.
That's it.
There's no electronics anywhere.
You clean the filter.
You put new injector tips on.
And this thing will run millions of miles before it needs a serious rebuild.
On cold mornings, you got to start it with ether.
You hand prime the fuel system.
It's been sitting.
You let it idle for 10 minutes and away you go with an engine block that weighs more than a Volkswagen Beetle.
The roads underneath you are U.S. or I've got to
let me grab something for you.
I just want to show you how big these pistons are.
Oh boy.
Okay.
And this is from this particular comment.
This is not from this thing.
Just to give you a perspective of how big the pistons are in these things.
It's pretty big.
This is the piston out of a...
I don't have a small piston, but normally they're much smaller than this.
What's this thing?
That's pretty beefy.
Look at, look, look.
It's a common right here.
Right there.
It says common.
There you go.
So this is...
Wonder what engine that's from.
I don't know my...
I'm not sure what this is all about.
Look at that thing.
Yeah.
Do you think that's what that means?
Well, I mean, look at it.
It's got...
I suppose, yeah, you're right.
Yep.
This thing weighs 65 pounds, six pounds.
Yeah, that's why revs aren't a thing, Chris.
It's quite heavy.
So the roads underneath you, as you drive along in your cab over Blanzer,
U.S. routes, Eisenhower signs a highway accident 56, but the network?
Not there.
Yeah.
You're on route 66.
U.S. 30, U.S. 40, U.S. 1.
You're crossing an actual continent with no freeways.
You're charming and down mounds.
The route does not go around them.
It goes over the Donner Pass, the Great Wolf Creek Cabbage,
otherwise known as Dead Man's Pass.
Eisenhower Tunnel will not be built for another 18 years.
So instead, you drop over a leveling pass at almost 12,000 feet with 70,000 pounds behind you.
All right.
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You stop where you can.
The truck stop in 1955 is not the Chrome and Wi-Fi travel plaza of today.
Gosh, the truck stops are so weird now.
Like you go into loves and it's just-
Yeah, I don't get the whole, the like renaissance obsession, you know what I mean?
Like swords and chain mail and other weird stuff.
So I used to look for the old truck stop vibes when I would drive across the country.
And they just don't really exist anymore.
They've been kind of killed by like loves and flying J and stuff like that.
Right.
But it was old ones and they were just, it was literally like
knick-knacks that were dusty, pornography and caffeine pills.
It's kind of like-
There was a cafe next door and maybe some dirty showers.
Yep.
So they usually had a diner attached to a fuel island with a gravel lot and a few sodium lamps
lighting everything up.
Inside, there was a counter, a row of booths, a jukebox, two pinball machines and a haze of
cigarette smoke that never disapeared.
It's smoking.
The waitress is smoking.
The cook is smoking.
The drivers on either side of you are smoking.
The ashtray is getting empty every hour and they're full again in 20 minutes.
Hi, you drink coffee black because you're a man.
You catch four hours of sleep in your bunk or stretched out across the bunch of your truck.
A shower's a quarter at the bigger stops and it's probably cold for the first 30 seconds to a minute.
You buy a pack of hallmalls and a tin of Copenhagen and a sandwich for the road and you go.
The men around you are all men.
Some are vets back from Korea or Europe.
Some have hands missing fingers.
A lot of them take Benzedrine to stay awake.
Dexys and white crosses are prescribed by doctors who never asked a question.
They're handed out by dispatchers who needed the load delivered.
The lifestyle makes a hard man, whether you want it to be or not.
The teamsters union is at the peak of its power.
Jimmy Hoffa is its president from 57 until he goes to prison for jury tampering in 67.
The union is what holds this fragile labor force together.
The pension fund is what gets a driver's family through the years he spends on the road.
By the time you reach the 70s, the truck stop has gotten louder and rougher around the edges.
See radios crackle in every cab.
The magazine rack at the counter sells special magazines.
Women in the lot have a special name now and the drivers have a name for them.
None of this has anything to do with our story, but it is the world the story flows into.
Hard men, dirty places, long halls, sketchy margins and dangerous work.
All of it adds up.
Engine that does not rev, the gearbox that takes both hands, both feet.
Sometimes, probably for me, do I want to drive a twin stick?
If you've got a bunk, if you're lucky and the cab is safe.
Mostly you don't, I mean, you never, these guys don't use the clutch either, by the way.
You float shipped all of it.
Yeah, you can. Yeah, yeah.
The cab on top of the axle and the bunk, sir, if you're lucky and the diet is terrible
and the smoke is everywhere and you're taking Benny's and of course there's the lot lizards to keep you company.
The average life expectancy of a long haul driver in this era is 61 years.
I'm sorry. Yeah.
The national average for an American man is closer to 78.
Yeah. 15, 17 year difference.
It's heart disease, lung cancer, sleep at night, accidents, runaways.
The long slow grinding of a body that never gets to put itself down.
Most of these guys, the ones you saw at the counter in Wyoming
will not see their grandkids graduate.
It takes skill, yes, but more it takes grit.
Man knows what he signed up for and accepts the bill.
At every pass he crests, he starts doing math.
Air brakes at the time are standard.
They are better than what was on the truck on Cajon Pass, but they are still cast iron drums and friction pads.
Mm hmm.
To national brakes.
A loaded combination at the top of a 6% grade is carrying enormous kinetic energy, Jake.
You're going to ask those drums to convert that energy into heat.
It's all heat.
It's all heat and they will convert it into heat until they can't.
Brake fade is not a warning light.
It is the moment your pedal goes soft halfway down the hill and you do not know how far the pedal will go
when you push it next.
After that, you have a couple of minutes to find a runaway ramp or you just run out of road.
Back in the day, drivers died this way by the masses every year.
When did the runaway ramps become a thing?
Are we getting there?
That was, I mean, they had them right away.
I mean, those were, they're still there today.
They're still used if systems fail, but they're not used like they were used to.
There's pictures of trucks and videos of them going into these things.
So the thing, what year are we at here?
We're all over the place.
We're back in 1955.
Okay, cool.
The thing classy as billing does not exist yet.
The promise is not yet kept.
So a driver's options on a grade in 1955 are gear it down low before the top and hold your nuts as
you ride the descent with intermittent stabs at the pedal to let the drums cool.
Pray and pick out the runway ramp before you need it.
That is the world.
So basically what these guys would do is, as you got more experienced with the truck,
you would learn like, okay, here on this pass, I got a break here.
Okay, I got a coast here.
I got a break here.
And you would learn, you know, the, the rhythm and the cadence of basically using your brakes,
not user breaks, slow way down, let off and coast and engine break.
Yep.
Meanwhile, in a basement in Sausalito, California with a view of San Francisco Bay
through a small window on a lathe, Klessy Cummins is working on the way out of this.
He has been working on it since his brakes gave out on Cajon Pass 24 years earlier.
He's not at his company anymore.
The Cummins engine company has moved on without him.
In 1955, he eased out as chairman.
The Irwin family installed professional management, J Irwin Miller,
the great nephew of Klessy's original backer, and he runs the place.
He and Klessy do not see eye to eye on direction.
There were a lot of disagreements, eventually some divorce.
And Klessy moves to California and just decides to keep inventing.
He is not alone in that basement.
His youngest son Lyle works beside him.
He has a mechanical engineering degree.
He's sharp, patient, and probably a better son than Klessy probably deserves.
He formed a company together called Cummins Enterprises.
They are father and son with one single problem to solve.
He is reading the same news the truckers are reading.
The runaways, break fires, fail grades.
He knows the answer and he's been moving forward with it for two and a half decades.
The breakthrough, when it comes, is quite elegant.
Cummins and Detroit engines have a third lobe on the camshaft,
the one that activates the fuel injector.
Klessy's device piggybacks on that existing motion.
A hydraulic linkage transfers it to the exhaust valve at the top of every compression stroke.
The valve cracks open.
The compressed air dumps out.
The power-producing diesel becomes a power-absorbing air compressor on demand.
The mechanical heart of the device is just borrowed motion
from the part of the engine that was already there.
The idea comes to him in 1957.
The full patent takes until November of 1965 to be granted.
Of course, he takes it to his old company first.
They pass.
The reasons get told ways depending on who's telling them.
Cummins was an engine company, not an accessory company.
This thing's loud.
The bridges had been burned.
Pick your version.
He takes it to Detroit diesel.
They too pass.
He takes it to other engine manufacturers.
Everyone passes.
Every major heavy-duty engine maker in America has a chance.
And they all look away.
Then Klessy's nephew makes a phone call.
The nephew, as it happens, is dating the daughter of the vice president
of Jacobs Manufacturing.
He's dating the daughter.
Jacobs makes.
If you've ever tried to drill that, you have touched in Jacobs Chuck.
I've seen that on old Chucks in America.
The nephew mentioned that there's an old man in California
with a heavy-duty, heavy-duty diesel safety device.
No way you'll manufacture the thing.
So Jacobs sends a team out west.
Klessy demonstrates the device on a yacht.
The man whose brakes burned out coming down a mountain in 1931
is now demonstrating the cure to a drill truck company
on a boat he rebuilt himself in the San Francisco Bay.
In December of 1959, they signed an option agreement.
In April of 1960, Jacobs Manufacturing establishes a new division.
They name it after him.
The Klessy L. Cummins division.
The first production units are built for that Cummins NH series engine
we talked about earlier and it rolls off the line in 1961.
The Detroit diesel 71 series follows shortly after.
Real-world testing happens on trucks owned by Sheldon Oil, Consolidated Freightways,
Pacific Intermountain Express, Willig, ONC, etc.
11 distributors sign on to sell the device.
The first logo has two Cs intertwined for Klessy Cummins over a mountain peak with two mules.
This is pretty sure if you can find that original logo. I'd love to see it.
That's cool.
Word starts to travel.
The conversion happens slowly, mountain by mountain, fleet by fleet.
A driver hears about it from another driver at a counter in Wyoming.
You saw a guy use one on Cabbage Pass.
That guy never touched the brake pedal.
Trucks take cool all the way down.
Driver got out at the bottom and lit a cigarette like nothing happened.
World troubles at the speed of CB radio and black coffee.
By the late 60s, the device is standard equipment on serious mountain riding trucks.
By the 70s, you could not sell a class 8 without one.
The thing Klessy built on a lathe in a Sausalito basement is now on every long haul truck in the country.
This principle, however, is not new.
In 1905, the British car maker Rover built a system on its 1620 1905.
So it's auxiliary camshaft, modified exhaust lobes, very similar thing,
but it didn't scale and got forgotten.
I wonder if somehow Klessy just had the same idea.
Did he see this Rover thing?
Because he reinvented the principle for diesel and scaled it up and made it for
1,000 pounds of moving truck.
So I want to talk a little bit about how this works.
Go ahead.
So the Rover version, was that also for a diesel or does that for a...
It was for gasoline.
It was just an optional engine retarder, basically.
Yeah.
Yeah.
Another rabbit hole.
So I want to talk a second about a diesel and why this is necessary.
So if you're engine, you can engine brake in a gas car way better than a diesel.
Let me explain why.
Diesel does not slow down when you lift off the throttle because...
Do you know why, Jake?
There's no throttle plate.
There's no restrictor.
No throttle plate.
There's nothing restricting the flow into the cylinders.
Take your foot off the fuel and the engine jeeps just keeps spinning.
That is why a runaway diesel is a runaway.
Engine is not on your side.
Yes, you can engine brake some with a diesel, but it's not the same as...
Imagine if you had a gasoline car with 20 to 1 compression.
You let off the gas and...
I mean, it would have a serious engine brake.
So a couple of distinctions.
A runaway, you're talking a runaway truck, not a runaway engine.
That is a whole different phenomenon.
Which, have you experienced that runaway?
I have.
I was sitting at a stoplight in my Volkswagen diesel rabble.
Wow, Volkswagen diesel rabble.
Someone called 911.
The head gas failed and it just started running away at the intersection.
Obviously, you turn...
I didn't know what it was happening.
I was like a teenager.
I'm like, what's happening?
I didn't know that you just, you know, could get out and put your hand over the thing.
Like I had no idea what was going on.
So it just...
And dude, the amount of smoke generated from this...
First because it's literally burning the engine's oil.
Yes, I was driving on the freeway and it was like...
And I'm like, whoa!
You know, because I've already got a floor.
I already have it floored because it will go any faster.
And all of a sudden it's going faster than it's ever gone.
But only for like a few seconds.
I'm like, well, that's weird.
How could I recreate that regularly?
Of course, at the stoplight it filled the whole intersection with smoke.
Fire department showed up.
Someone called the fire department and it's just like, oh, it was just such a thing.
But that was the start of getting rid of that engine.
And we bought a TDI that was supposed to replace it.
And that TDI is now in my trooper.
Oh, that's cool.
Yeah.
So that's how that worked out.
Full circle.
Yes.
So here's what the device does.
Okay, I want to explain this.
I try to think of a really easy way to explain this.
Think about pumping up a bicycle tire.
You compress the air on every downstroke.
If the cap is on, the air pushes back and what you put in comes back into your hand.
Compress release, compress release, right?
You're just, you're really not doing much work other than compressing and releasing.
You can pump a long time until your arms eventually quit.
Now imagine someone walks over and pulls the valve cap off at the top of every stroke.
The air just dumps out.
You compress hard, but you get nothing back.
You're drawing the work both directions.
That is what is happening inside of a diesel engine.
Here's where the engineering has gotten honest away.
Klessy probably did not fully imagine the modern high output versions of this device.
The ones bolted the freight crossing of the country tonight
can produce more retarding force than the engine produces forward power.
The thing that drags you down a mountain can pull harder than the thing that drives you up one.
The same iron, same cylinder, same air doing twice the work in two opposite directions,
right? So it's using both compression and also the negative force on the downstroke,
not just the single downstroke, I guess it would have been on the previous version.
So you're getting twice as much work being done.
If you go to YouTube right now, which I found this unbelievable,
there are pages and pages of compilations of nothing but this sound.
Trucks tunnel barks isolated hours of it.
People just standing there filming as trucks go by.
People watching it on a loop and I do not get it.
To me, this is a jackhammer at the bottom of the canyon.
It's distinctive, but it is not particularly beautiful.
It does not sound good.
But diesel's in general don't.
So well, my truck sounds cool because it has a diesel.
It has a turbo whoosh.
I like, I love my turbo in my school and my diesel.
But people fall in love with the sound of the compressed air going somewhere.
It was not a moment ago.
As we know, turbo guys do the same thing with blow off valves.
It's different engineering, of course, but it's the same tribal attachment to the noise.
Tuna cars aftermarket valves that vet louder than anything the factory ever shipped.
Truckers themselves run bigger pipes for the same reason.
The factory version is much too polite.
The sound is the engineering being honest about what just happened in the engine.
There's a whole subculture in two different worlds that grew up loving exactly that honesty.
Whether it sounds good or not is beside the point.
Miss producer, by the way, just says she loves that sound.
Can you pull, can you pull up a video, Miss producer?
Yeah, fine one.
Yeah, fine one.
We'll, we'll play it as we, as we go here.
And then, of course, are you going to talk about the entire now?
Like it's, you see the signs that we're no Jake break.
A driver uses it properly might never touch the brake pedal at all on a mountain pass.
The brake hardware stays cool and it stays ready for the moments it's actually needed.
Drivers start getting twice the life out of a set of foundation breaks,
but the money is the small story.
The big story is the runaway that did not happen.
It's a trailer that didn't jack knife.
What I found interesting is that there's, uh, there's no
federal regulator has ever mandated this device.
It's so really, you don't even have to do it.
They don't need to.
The market adopted and drivers adopted it.
Nobody wanted to die.
So everybody's on every truck.
You can't really buy one without it.
No, that's interesting.
By the time the seventies are over, let's go.
Is there, she forgot to share the audio of the video.
Oh no.
Yep.
Is this like a, is this a Jake breaking competition?
It is.
Isn't it?
You have to click share audio when you share this.
We can't hear that's what this, this is a Jake breaking competition.
I think I don't know how you compete, but that's what I'm hoping this is.
Well, we don't get to hear her.
Mrs. producer, stop sharing it and reshare it with audio.
Fix it, fix it, make it work.
Share it again.
You have to click share audio.
Well, she does that.
Chris, you know, a lot of these truckers, you need to kind of know like the elevation
that you're going to be at, or you don't need to know, but it'd be nice to know.
Oh, here we go.
Here we go.
It's accelerating, accelerating.
Holy shit.
Out.
Wow.
What, can you turn your mic on and tell us what this video is?
Because I have a microphone.
Oh.
We got a cab over single.
It's literally a, yeah, it's literally a Jake break.
It's a Jake break competition.
I don't get it.
All right.
You can stop sharing that, Mrs. producer.
By the time the 70s are hold on, hold on.
What I was going to say is that, you know, if you need to know when to use your Jake breaks,
one good thing about on X off-road is it also shows you elevation.
If you're looking for the best app for navigating your next adventure or where to
use your Jake breaks, look no further than on X off-road.
They have over 750,000 miles of trails and comprehensive offline maps.
So you can explore without worrying about cell service.
The app features trail ratings, which we know are actually verified by their actual
people out there trying out these trails.
It's not just a guess.
So, you know, if you can take your 9-11 there, or if this is a full on articulating rock
crawler only trail, there's a discover tool.
There's land boundaries.
You always know where you can legally off-road, camp and explore.
You can stay connected with cell service layers.
Why is Chris thinking about things?
Yes.
You have tools like route builder, waypoint marking,
real-time updates and route sharing.
So you're fully equipped for any adventure.
Try it for free for seven days and hit the road with confidence.
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All right.
I was trying to think if there was a way to put a Jake break on a diesel that doesn't
have them, but then if it's runoff, I would have to do it mechanically.
Like a mechanical pump.
Well, it's going to do without putting a comment.
So, how would I do it on a diesel without the lobe that'll run on them?
No, but there is.
No, I know.
There is exhaust actuator to move the camshaft over.
Right.
There are different versions of like, so there's a compression release engine break,
which is what you're talking about.
But isn't there also just like an exhaust back pressure valve?
Wasn't that a previous version of it where it would literally just think of a valve in the
exhaust manifold?
So all of a sudden you're just pushing exhaust?
I do not know.
I'm going to look at this maybe.
You can continue our story if you want to.
All right.
By the time the 70s are over, you cannot sell a heavy-duty diesel without one of these.
Jacob has built more than 9 million of these since 1961.
Wow.
Every comments X-15 making freight today.
Every Detroit diesel and almost every diesel running this country's mountains.
The man on Cajon Pass in 1931 made one descent that almost killed him.
Every truck driver since it's gotten to make that descent and live to tell their kids about it.
Most people will never know any of this unless they listen to this podcast.
Most people will never hear Klessy Cummins' name.
You've seen the signs in every mountain town, every off-ramp onto a quiet main street.
And that is the only way anyone knows what this stuff is called.
It says no engine brake or in some places the more specific version.
No Jake brake.
Yeah.
Sorry.
Has one more turn in April.
It is April 2022.
Cummins Incorporated, the company that turned Klessy down in the late 50s,
acquires Jacob's vehicle systems.
61 years after the rejection, the Jake brake comes home to the company Klessy founded.
The original patent is now in display at the Cummins Heritage Center
in Columbus, Indiana, 46 miles south of the Indianapolis Motor Speedway,
where the kid worked the pit lane of the very first 500, 46 miles, 111 years later.
That promise on Cajon Pass, the lathe in California,
the patent, his old company turned down, the Chuck company that picked it up,
the mountain by mountain conversion, 9000000 units, the runaways that never happened.
That is the Jake brake.
Love it.
Klessy Cummins died in 1961.
Thanks, Klessy.
Yeah.
So wait, he died in 61.
68, sorry.
68.
68.
But he really didn't see quite how prolific this became.
He really didn't.
He really never got to see it.
Interesting.
You can add, by the way, an exhaust brake to your TDI trooper,
which is just like I'm talking about a valve after your exhaust manifold,
but you're right, the Jacob's systems.
It's not going to sound cool though.
No, it probably doesn't sound like anything.
It just sounds like just quieter because you're literally restricting exhaust.
You're turning your exhaust off.
That's no fun at all.
All right, guys, that's it for this week.
I hope you enjoyed that, Jake.
I hope you think diesels are cooler than you did before this episode started.
I do love the mechanical aspects of the Jake brake specifically.
Like that is very cool.
But not the mechanical aspects of a diesel engine itself.
No, no, no, just the Jake brake.
No, I like the simplicity of a diesel, sure, in the torque.
But like, I just, no, you're not going to convince me it's a good...
Oh, what else we got?
What else we got?
Oh, that's a good one.
Yep.
This dude, like, came out on his porch.
He heard this thing coming and ran out.
Yeah, let's go.
On the side of the road, this guy going to come.
I don't know.
I never knew until I started researching this how much people love the sound of the Jake brake.
Okay, so there's a whole thing.
It's a whole thing, man.
Now, when you're out and about and you hear the Jake brake, you can judge people
by the sound of their Jake brake.
If it's quiet and you barely hear it, I don't, dude's pretty lame.
But I guarantee you those dudes with the big stacks and...
Yeah, like the lime green trucks with all the lights.
They probably got a good sound of Jake brake.
Okay, yeah, I guess so.
Now we will see you all next week.
Take care, guys.
About this episode
A runaway diesel story kicks things off: the head “just started running away at the intersection,” filling the stoplight with smoke until the “fire department showed up.” The show then zooms out to 1931 Cajon Pass and the evolution of heavy-truck control—brakes fading, downshifting, and even forcing water into cylinders—before connecting it to why diesels dominated by 1955. Later, the episode explains diesel engine braking and the “Jake brake,” including how it became standard on mountain trucks.
Coming off a six percent grade in 1955, your brakes were a countdown. By the seventies, they were a backup system. The story of the man who built the thing that took the death out of the descent.
