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Decoding Ken Block’s Hoonicorn RTR

Get inside the minds behind the Hoonicorn RTR project to find out how the most famous car on the Internet was built.

Inside the Ken Block '65 Mustang Hoonicorn RTR

For two years it was kept a secret.


Like building a spaceship around an astronaut, this million-dollar racecar was built around a driver, the needs of his craft and the exploration of a genre.


No one outside the very small and tight-knit circle knew about the project; even best friends were left out. Shrouded in secrecy, the six-cylinder 1965 Mustang Notchback 3-speed was cut and sewn back together into the Hoonicorn RTR, a hybrid race and demo car.


Cell phones and computers provide access to such an incredibly fast-paced information network that keeping anything hidden from prying eyes is becoming increasingly rare—and a Ken Block Gymkhana car is on another level of vulnerability. With over a quarter of a billion views on the Gymkhana franchise, the reveal of the next-generation car is on par with anything the automakers can throw out, which is why the Hoonicorn RTR was such a big surprise to the world. It’s unconventional from almost every angle and a big departure from Ken’s turbocharged, four-cylinder hatchbacks.


Underneath the Mustang body—only the A pillar, B pillar and roof remain original—a fascinatingly complex web of brilliant engineering and foresight containing 800 horsepower, all-wheel drive and rally-spec demands to make it usable. But what really makes up this build? How did the vision become a reality? And what parts made this monster come to life? That’s what we went to find out, driving through the desert in order to make our appointment with this badass ride in Salt Lake City.

Design Theory Design Theory Design Theory Design Theory

Design Theory


“I needed it to look aggressive and mean. It was really to get inside the head of Ken and Vaughn.”


Andy Blackmore of Andy Blackmore Design speaks in a classically soft, clear, concise British tone. He’s no stranger to designing high-profile automobiles: a few McLaren F1 GTRs, the Turner Motorsports Z4, the SEMA designer challenge with the Scion, and Vaughn Gittin Jr.’s RTR-X are just some of the builds in his profile. Normally, designers like Blackmore try to go for a clean aesthetic when approaching a build, but the Hoonicorn RTR was an outlier.


“I needed it to look aggressive and mean and not as clean as the RTR-X,” Blackmore admits. “It was really to get inside the heads of Ken and Vaughn.” This became a drawn-out process as revisions and schedules weren’t aligning—but also a blessing, because normally designers don’t have the time this one necessitated for back and forth with such particular direction.


Blackmore would end up sending 10-12 final renders and countless detail changes for splitters, exhaust, intakes and fenders. He explains: “I drew a lot of inspiration from ’60s muscle-car builds—nice and clean, [from] things you’d see at SEMA to things that were made in the back of a garage. We have the undercuts in the fender at the rear, and that was influenced by WRC cars and, nowadays, FIA GT3 cars. You’re getting little elements there that are a big influence on the car.”


The biggest challenge with the design was nailing the stance and getting on the same page as Block and Gittin. “Sketching it up, I’d be getting feedback like, ‘No, it needs to be wider than that!’ and then being like, ‘Oh, oooookay,’” Blackmore jokingly recalls. “From an engineering perspective, one of the biggest challenges was ride height and how low the car was. There were some late changes in over-fender form toward the end based on engineering.”

CAD to Rad CAD to Rad CAD to Rad

CAD to Rad

“I wasn’t trying to throw any strange electronics and an active suspension, active aero, active differentials, any of that stuff [into the car],” Block says. “When you look at it mechanically, and look inside the content of the car, it’s really all pretty simple. Like, let’s take the shit that we know and do the best package that we can make function—make it fucking awesome!”


Relying on the expertise of some really smart people, the task of fitting an AWD system to a Mustang with a race V8 became an exercise in chassis packaging.


“It was a bit of a jigsaw puzzle and required an open mind to adapt.”


With the help of Hoonigan Racing Team Director Derek Dauncy—who’s been cutting his teeth in top-tier rally since the ’90s—as well as Vaughn Gittin Jr.'s Mustang-honing RTR division, ASD Motorsport of Charlotte, North Carolina, and Sadev racing transmissions, they figured out the correct gearbox to use with the V8 and get the prop shafts around the engine and working properly. It was paramount for Block and Dauncy that the Hoonicorn RTR work for both filming and in a future form of competition (more on that later).


ASD—who had not had prior experience with all-wheel drive—worked alongside Dauncy to implement the Sadev SC90-24/170 sequential box in the Hoonicorn RTR. (Sadev also supplies the Hoonigan team with transmissions for the rally cross and rally cars). This $28,000 gearbox isn’t your grandfather’s Powerglide; it’s a Dakar-winning metal masterpiece that only has roughly 300 units in circulation. After looking at the massive V8 engine power delivery with the available torque range, they decided to go with a wider gear to help spread load and demand.


Click here for a full-resolution download link to the chassis image (warning it might blow your mind).

Packaging Packaging Packaging Packaging Packaging


“It was a bit of a jigsaw puzzle and required an open mind to adapt as the project progressed to tie everything down,” Dauncy admits. “Ian [Stewart] from ASD took what we wanted and needed from the car, and the team ran with it.”


Working from the beginning of the project, Maxime Lecoindre of Sadev had to decide which transmission would fit best based on all the calculated factors before a single driveshaft turned.


“You have to consider the power of the engine, but it’s important to consider the value of power [and what the car is able to put to the ground],” expounds Lecoindre. He explains it’s not necessarily the engine power that’s important but the ability of the transmission to put the power to the wheels. “Because the wheels are spinning most of the time, you will never have the torque or load opposition on the transmission: resistance of the ground and the torque of the engine.”


With the major hurdles of design and theory behind them, the build began.


“It really came down to packaging: We had a big-ass V8 engine, and we had diffs that had to be in front of it,” states Vaughn Gittin Jr., creator of the design and performance firm Mustang RTR. “Sadev was proven. Packaging became the challenge.”

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Gymkhana Built

SolidWorks computer-aided design (CAD) was implemented first and foremost by ASD to get an idea of where key parts needed to go and exactly how the packaging would work. Then ASD hired longtime friend and master fabricator Jason Burke of New Zealand to form the malleable sheet-metal molds for future carbon-fiber autoclaving. Gittin is adamant that you don’t find people who can do that type of metalwork anymore, and was actually sad to see the metal pieces used for the molds destroyed. “I’m a huge metal nerd, and unfortunately, during the mold-making process, a lot of those metal panels were trashed,” Gittin reminisces.


Instead of staffing a full-time carbon-fiber fabricator, they instead chose to outsource the work (again, secret sauce), but because of the secrecy of the project, every part was taken to the fabricator piece by piece, never as a whole, always leaving him without enough information even to guess what it was for.


Once they had the motor—the rippin’ 410-cubic-inch Roush Yates sprint-car engine—chosen for propulsion, they had to move the engine back far enough so the drivetrain could go right around it, with the diffs in front to propel both wheels. The engine produces a quite insane 845 horsepower and 720 lb.-ft. of torque, and it is essentially Gittin’s drift car motor as well; something that he's been running professionally since 2012. Mate that to the Kinsler ITBs and, well, the sound is quite spectacular.


This set up the next stage that makes the Hoonicorn RTR look so good and react so well: the pushrod suspension.


Though Block didn’t have any particular suspension setup in mind when it came to decision time (he left the engineering to RTR and ASD), team director Dauncy made sure options were left open: “I wanted the car to be used not just for Gymkhana Seven but in some form of competition in the future. We managed this with the excellent design on the suspension,” he admits. Block confirms, “It was a bit of a shot in the dark as far as how the setup would work with the car, with the V8, and how it would drive to do the things I wanted it to do.”

HHIC Approved HHIC Approved HHIC Approved HHIC Approved HHIC Approved

HHIC Approved

The final setup consisted of an inboard, double-wishbone pushrod suspension setup with designed geometry and components concealed within a custom space-frame tubular chassis, all of which were developed in-house by ASD.


“[The engineering team] really did an exceptional job. It’s amazing that car had only literally 10 minutes of testing just months before I had to film.”


“It wasn’t perfect but it was quite close,” says Block. “[The suspension] was on the soft side, but as far as how we got traction and balance, the front and back power delivery with the differentials, and the feel of the car with the weight was quite different from other cars I’ve used. The funny thing is, we work with one of the most advanced rally cars in the world. It’s the most up-to-date technology you can possibly get to go fast on tarmac, gravel and snow. It’s so dynamic; it’s all built for that chassis. But if you take that technology out of there and throw it into something low, squatted, with room for suspension and a giant V8, it’s really a difficult task to take everything about what I love that the Fiesta does and put it into this ’60s-style Mustang. [The engineering team] really did an exceptional job. It’s amazing that car had only literally 10 minutes of testing just months before I had to film.”

Engine Details Engine Details Engine Details Engine Details Engine Details

Engine Details

Both blatant and subtle touches all over the car make the Hoonicorn RTR truly special. From the one-off Autometer gauges, Fifteen52 R43 wheels, and special livery made by a friend of Block’s in the industry, there’s an abundance of cues taken from both motorsport and the automotive landscape—not to mention the parts list, which is every homegrown racer’s wet dream.


Block worked with Fifteen52 to choose the wheel that would be the face (no pun intended) of the Hoonicorn RTR. Look closely at the R43 cast-monoblock wheels and you’ll notice a reversed design of the iconic Ferrari F40 Speedline wheels. Block is also going to be launching the R43, his first signature cast wheel, in a line alongside Fifteen52’s Turbomac. Not only was Gymkhana Seven the unveiling of a completely new car, it was the launching pad of the new wheel in celebration of the seventh installment.

Interior Details Interior Details Interior Details Interior Details Interior Details

Interior Details

“The project took longer than expected, but it was clear from a very early point that this car would be epic,” Dauncy proudly admits.


Regardless of what you think of the newest installment of Gymkhana, there’s no doubt this is Block’s best Gymkhana car yet, and ranks as one of the greatest custom car builds to date. Ken Block is afterall a marketing genius. It’s the most conceptual, innovative and team-driven car so far that’s focused on two particular functions: to make kick-ass videos and, if we’re all lucky as automotive fans, to race. We know Gymkhana 7 isn't the last we've seen of the Hoonicorn RTR.


Hoonicorn RTR Specs:

Engine: Roush Yates 6.7-liter, 410 cubic-inch V8

Horsepower: 845

Torque: 720

Transmission: Sadev SC90-24 4WD 6-speed sequential transmission

Suspension: Custom valved JRI Dampers and Eibach Springs

Weight: 2,888 pounds (estimated)

Top speed: 120mph (gearing limited)

0-60: 2-2.5 seconds (estimated)


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