TheThump Truck – A 23,000lb Kenworth That’s About to Run 13s (w/video)

TheThump Truck – A 23,000lb Kenworth That’s About to Run 13s (w/video)

With this Labor Day Weekend’s “theme” around here being working vehicles, we knew we couldn’t pass up another chance to share this insane tire shredding dump truck we have dubbed the Thump Truck. It’s got over 1000 horsepower at the tires and is currently working on getting deep into the 13 second zone. Oh yeah, it weighs 23,000 lbs remember. And it hauls dirt and gravel every day as well. Check it out.

(Photos by Dave Nutting and Brian Lohnes) – This thing is truly insane. A 23,000lb behemoth making 1,000hp at the tire that defies logic, the known laws of physics, and all levels of common sense. On the day photog Dave Nutting and I met Leon Smith, the owner of this 1998 Kenworth T-800 truck, it was way below zero. The wind was howling at the huge gravel pit we were shooting the photos at, the pyrometer on the dash of the truck was hovering near zero and the big diesel motor was not all that happy. Leon had spiked the gas tank with a big dose of anti-gelling agent, which was good because we had already spotted at least one dead truck with a tank full of goo on the side of the road. Dave and I were hoping to get some burnout shots but we didn’t want Leon to wound the motor. I threw a non-chalant, “Can you do a burnout of two without hurting it?” at Leon and his immediate response was, “Oh yeah, we can do burnouts.” GAME ON!

This is a Kenworth dump truck doing burnouts!

This is the most BangShift approved hot rod dump truck on Earth, mainly because Leon has forged a long and lonely trail of performance innovations with a relatively unloved engine family, good old fashion Yankee ingenuity, and he still uses the truck at work every day.

Cutting to the chase, this truck has run the quarter mile in 14.2 seconds at over 98mph with an Eaton-Fuller 18-speed manual transmission! Most likely that will wipe the floor with whatever you drove to work in and it will eat a lot of street rods alive. With a new slate of upgrades for 2012, Leon hopes to punch the 10-ton truck into the 13 second zone. Rudolph Diesel just threw up Dio horns in his grave. The larger question within these shockingly awesome numbers is pretty glaring, though. How the hell did this happen? How did a guy become obsessed with making a dump truck haul 12 yards of ass at the drag strip?


The Long Ride Home – 

One of the major reasons that this truck became a speed machine is the fact that it was quite the opposite of speedy when Leon bought it. “I bought this truck in 2008 from a dealer in Colorado,” Smith said. “The truck was not a dump truck at that point, but a tractor that worked in New Mexico pulling double trailers. It had a 10-speed transmission, a 12.7L, 430hp, Detroit Series 60 engine and a governed speed of 58mph. That sucked pretty bad because we drove it home to Connecticut.” Leon had taken an old salt of a truck driver named Jack Boothby with him to help with the driving chores, but ol’ Jack didn’t get too much wheel time. “He kept telling me that he wanted to drive, but I just wanted to keep going. At one point I had to let him drive because I was so tired, but it was only for a few hours so I could have a nap,” Smith said with a laugh. “It took us a few days to get home and at that point we swapped in the 18-speed transmission, added the 12-yard dump body, and painted the truck, which was an awful shade of yellow when we drove it home.”

How Leon Caught the “big truck, big power” bug – 

This whole super sized hot rod bug is something you catch and then can’t ever be cured of. The needle got buried deep into Leon’s arm years ago when a man named Bob Davis was in need of help when his own hot rodded big rig puked a water pump. Leon and his friend Stacy Richardson fixed the truck for Davis and at the tender age of 18, Smith was allowed to take a short squirt in the driver’s seat. Of interest was the fact that at the time in the 1990s Davis had one of the baddest trucks in the country. Smith hauled tail on some small country roads around his Connecticut home and Davis was pretty impressed with the skills he saw. The two have been life long friends ever since and Leon Smith has been on a quest to bend the laws of physics even harder than his hero did! (Here’s a photo of the two dudes and their trucks!)


The modifications begin

Being a guy who had always been into fast cars his whole life, the idea of hopping the truck up came pretty naturally to Smith. “I was getting a lot of heat from guys who were saying that I would never get anywhere with this engine combo because they just didn’t make any power,” Smith said with a laugh. The Series 60 was Detroit’s first go at an electronically controlled diesel engine and it was a great piece but high performance was nowhere near the original intention of the engines. These were designed to be mileage masters and help to improve fleet efficiency. They were also built like anvils and could go a million miles before needing an overhaul, which was a number that other engine families at the time could only dream of.

Smith’s first modifications will sound familiar to modern hot rodders the world over, he started tweaking the ECM on the truck. Being that this is a diesel, ignition timing is not part of the equation, but injector timing is. By working with virtually stock engine components, like the turbo, Smith was able to coax more than 550hp to the wheels of the truck and for about 15 minutes that was enough. ” Once I started making more power, I of course, wanted to make more and more,” Smith said. “I then went to a larger turbocharger and was making about 650hp to the tire but with that turbo I didn’t have much of a power range to work with and this truck gets used every day so it was not ideal. The thing looked good on the dyno and stuff, but it was not a practical setup.”

It was at this point that Smith concocted a home built compound turbo system that he has been working with and tweaking on ever since. In race trim, with two turbos that even he would not give us details on, he is shoving more than 150lbs of boost through the engine. But we’re getting ahead of ourselves again.

A Band of Diesel Hot Rodding Henchmen Help Out

One does not just slap a couple of huge turbos onto a big diesel engine, zap a couple keys on a lap top, and then make 1,000hp. It ain’t that easy, kids. There have been countless hundreds of hours spent on working the huge cylinder head on the engine, installing and trying different camshafts, experimenting with injectors and other hard parts and these things don’t happen in a vacuum. Mike Pettit of Pettit Racing Engines in New Milford, Connecticut has become about as obsessed with this thing as Smith is. Pettit has been doing cylinder head work on this truck for a couple of years and is now as into toying with the giant Detroit head as the smaller heads he works with on the successful circle track and high performance street engines he builds.

Smith has had help from other friends as well, Curt Rice is a man who passed away but while he was around, lent his considerable brainpower to the Kenworth’s development as well as some trick parts and ideas on turbocharging and how to hot rod factory pieces to work in the extreme environments that Smith is asking them to work in.

Phillip Price of Pennsylvania’s Antrim Diesel Service has been a big part of this madness as well. Leon has had dyno time on the rollers at Antrim, laying down just a few numbers short of 1,000hp there. He has blown trucks up there and rebuilt them in record time to make drag races in other states as well.

There’s no such thing are drag slicks for a truck like this and traction is definitely the mortal enemy of the Kenworth. After years of spinning regular production tires for nearly the whole length of the track, Leon hooked up with Tri State Tire in Wallingford who has been helping Smith with recaps of varying compounds and sidewalls in an effort to get the truck to hook better. “Tri-State has been a huge help and his tires have been one of the most important parts of getting this truck to go quicker on the drag strip.”

Engineer Steve Trevitz has been an asset to the program as well. “Steve has come up with some great ideas and things to try which Curt Rice was able to put into practice,” Leon said. It is always cool when the brains and the brawn are able to work in harmony to make stupid huge power!

It should be noted that even with the better tires, the truck will still light the hides up on the track hundreds of feet into a run, “You can feel the truck shudder some and that is how I know the tires are spinning.” Did you just smile? We did.

Long story short, this effort has been a collaboration. Yes, Smith has the most time and work invested, but he knows that he’d never be where he is at without the help of friends as obsessed with diesel power as he is.

 Big Power and Bigger Secrecy in the Big Rig Drag Racing World

There is a very devout following with respect to racing these huge trucks. Guys are wild for them in Canada and all around the USA and you’d probably be surprised to know that there is a very high level of secrecy involved from truck to truck. Guys do not share a lot about their combos because virtually all of them are hard crafted and come from years of busted parts and broken wallets. Hoods are very rarely ever opened at these events because turbocharger setups and other valuable secrets are revealed that way. Hell, we have seen dudes standing guard while trucks are serviced before. With Leon being even farther out on exile island due to the running of the oddball Series 60 Detroit combo, detailed info on his motor and race turbo/fueling setup was scant. “It is different than what I use when the truck is at work,” Smith said. Point taken.

Here’s what we can tell you. When we were randomly throwing numbers at him with respect to the size of the turbos, he laughed at us when we mentioned 100mm inlet size. They are significantly larger than 100mm….each.  The “non-race” combo that is on the truck for the day to day grind of actually being an operational dump truck consists of an S400 and HX-82 feeding the beast. 

The truly amazing thing about this motor for us is that will little to no aftermarket support or parts of any type, outside of the turbos (and even those are usually modified production units), this whole engine is factory parts optimized and maximized to their limits. A recent compression ratio change came not from custom pistons but from countless hours of research to find a factory piston that would do what Leon wanted.

Smith likes to refer to the stuff he has done to the truck like the compound turbos, as “redneck engineering”, and it is easy to laugh at his sense of humor, but there is way more to it than that. This guy is smart with a capital brainiac. We left the Smith compound the day of the photo shoot pretty amazed at Leon’s understanding of his combo and the actual science and math behind it. He is a modest man who loves his hot rod, but don’t think for a minute this whole thing was an accident.

What is it Like to Speed in a Two Story Building –

You’ll see the video of this wild ass truck below, but allow a minute for us to explain what it is like to ride in, even with the tame “work” setup in the engine bay. It is a bit like sitting in the second story of your house and having the Almighty reach down and woosh you down the road with his hand. This truck makes literally thousands of ft/lbs of torque so the sensation is like nothing we have ever felt before. It just doesn’t stop coming and it does set you right back in the seat. Leon is a whiz with the gear lever and can shift the truck like it has a lenco in it. We thought for sure it was an automatic when we saw the drag race video because the shift are so surgical, but it isn’t. The dude makes throws that are more than a foot long look like short throw clicks. Dave Nutting was following us in his Subaru WRX and at one point when we stopped, I walked back to find him sitting there with eyes the size of pie plates. He was both amazed and horrified that the truck was not only running hard, but literally running away from him. He muttered something along the lines of never being able to show his face on a Subaru forum again if his car was outrun by a Kenworth dump truck. Idiotic laughter followed every full boogie blast Leon made in the truck.

The Big Finish! 

Leon has worked on a bunch of stuff this winter and he is hopeful that the truck will bust into the 13-second zone this Spring or Summer. We hope to be there to see him do it at one of the events he’ll be running up and down the east coast.

This truck is truly amazing and a testament to the ingenuity and tenacity of Leon to work an unloved and fairly disrespected combo into a genuine giant killer. A 23,000lb truck that runs 13s? DO WANT!



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