Kenworth Semi Built to Break Land-Speed Records Is the Coolest Way to Go 140 MPH

I’m a simple man: I love race cars and I love semi-trucks. Put the two together, and you have my attention. That’s what Australian speed freak Rob Waters has done with his W-Series Kenworth dubbed “The Prospector.” It’s specially built to run the salt flats at Lake Gairdner, and while its 142-mile-per-hour top speed might not sound that fast, it’s blistering for a big ol’ brick.

I stumbled upon The Prospector by way of this excellent mini-doc on the Roadboss TV YouTube channel. The cinematography is killer, with camera shots that make the rig look as slick as ever on the fine white salt. Those who have raced there say it’s even better than what you’ll find in Bonneville, and, at about 99 miles long, there’s plenty of space to run anything wide open—even a 30-foot-long semi with roughly 1,500 horsepower.

The 13-liter Caterpillar diesel inline-six was yanked out of a dump truck and mounted behind the Kenworth’s cab. On top of the custom frame being stretched significantly, the fiberglass hood is also a lot longer than stock, despite there being no engine underneath. It’s all done in the name of aerodynamics, which any land-speed racer will tell you is more important than sheer horsepower. Not that more engine output ever hurts, of course.

According to a video I found that was posted by Turbo Care, The Prospector gets 40 to 60 pounds of boost from an 88-millimeter BorgWarner S500SX turbo. All the piping is beautifully done, contrasting nicely with the red frame and searing yellow bodywork. The chrome pipes run the length of the frame aft of the cab, bellowing smoke until the power adder starts truly spooling. And the fuel tank? Yup, it’s a polished chrome beer keg.

Waters’ truck holds the Australian modified diesel top speed record, which isn’t bad for a machine that was assembled in just five months.

During one of the machine’s Speed Week 2025 runs, it started pulling hard to the side. As it turns out, the locking rear differential was borked, causing all the power to go through one drive wheel. It’s usually “straight as an arrow,” which tracks since everything about the truck was developed to do as much. They were able to repair it and keep the Kenworth from attempting a triple-digit donut as all that torque tried to make it turn.

Waters has been saying for years that the goal is to crack 150 mph and, eventually, 160 mph. That hasn’t quite happened yet, but it’d be unfair to say they’re having a bad time out there on the salt. Lake Gairdner appears to be a serene spot, free of the fanfare that floods Bonneville. They may never go faster than 142, but something tells me they’d be OK with that.

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