The engineering behind Dick Johnson's 635kW Limited Edition Mustang

“I’ve always loved something that has plenty of grunt,” Dick Johnson tells MOTOR over the phone, perhaps stating the obvious. This is the man who in his late 40s called a 500kW-plus Ford Sierra Cosworth his office and, thanks to a turbocharger that woke like an exploding bomb, constantly drove it on opposite lock around places like Bathurst.

But that was on track, the place where he crafted his legend in Australian touring cars – and in the hearts of Ford fans. Right now, though, we have him talking about things off the circuit and, in particular, a special edition road car known as the Ford Mustang Dick Johnson Limited Edition.

Although his CV is short in this arena, it’s well known. Not fully able to get a couple of factory Falcon projects off the ground, Dick Johnson Racing went out and built its own BA Falcon-based special edition back in 2004 known as the 320. Lauded for balance and refinement, it intended to lure the high-end HSV buyer, but in the end only 25 were made.

While hindsight might view that low production run as somewhat of a failure, today such exclusivity has been placed at the centre of the Mustang DJ LE (our abbreviation, not Johnson’s). “We thought initially we’d do 17,” Johnson says, referencing his famous race number, “but [we had] an opportunity to increase that to 30.” Buyers were signing up before they had so much as seen the car. Even at $180,000 each.

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Why would anyone feel compelled to spend almost three times the price of a standard Mustang? Well, besides the rarity of road cars from the now 74-year-old Queensland racing legend, or his Supercars racing team’s recent domination with a Mustang, it might have something to do with the key players behind the project.

Dick Johnson and Herrod announced the Limited Edition Mustang in November 2019

On one hand there was Ryan Story. He’s the local head of DJR Team Penske and someone who Johnson personally credits with “putting the procedures and financial aspect together”, adding “it’s not just a matter of getting a Mustang and hotting it up, there’s a lot of other organisations that go into it, with putting all the bits and pieces together”.

But on the other hand, when you do need to hot up a Mustang, there’s Rob Herrod. Herrod Performance was the other architect behind the DJR 320’s package all those years ago. That, along with his work on the right-hand drive Mustang program and his close relationship with Ford and its performance parts suppliers, made him the only choice. But the gang wasn’t back together just yet.

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Originally Herrod had to avoid the opportunity since he was occupied with another important one for Ford Australia. “I was working away confidentially with Ford on [Mustang] R-Spec,” Herrod tells us. “I couldn’t let anyone know I was working on R-Spec and had no time to work on a limited-edition Dick Johnson Mustang. So I had to keep diverting the question of ‘when are we going to do a road car?’”

It was only when the Mustang R-Spec project eased its demand on Herrod’s focus that he could begin envisioning what sort of car to build for Johnson. In a way, while the R-Spec originally hindered the project, its existence guided the concept. Both men knew the DJ LE could not compete with the R-Spec on price, and luckily Ford had no plans to build a right-hand drive Shelby Mustang GT500 anytime soon. The sky became the limit.

Herrod then dreamed up two options: a base car with a lower output and less aggressive exterior package, or a road-going monster with reworked engine internals, a feral supercharger, optional bolt-in roll-cage and what Herrod calls a “super dooper” wing. Obviously, Johnson was most keen on the latter.

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It’s from here, though, that Herrod was left alone to develop the package, pouring the knowledge gained from years of Mustang technical development into one ultimate version. But to hit the power figure he had in his head, he needed to push as much air as possible into the Mustang’s Coyote 5.0-litre V8 and extract the remnants out the back.

On the former point, Herrod bolted on an intercooled Whipple supercharger measuring 3.0 litres in capacity, or 350cc larger than the Roush unit in an R-Spec, which he says is very efficient. It breathes through a monstrous 132mm throttle body; that’s 37 per cent larger than the standard GT’s 82mm unit, and it features a custom end-module.

With the V8’s gullet widened, Herrod uprated the supercharger’s pulley to force in more boost (11psi). Then the primary injectors were upgraded to saturate the extra air with enough fuel, whereas the direct-injection injectors were left alone. Finally, a stronger fuel pump that Herrod developed over the years with TI Automotive, owners of Walbro, supplies enough juice from the tank.

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However, TI Automotive wasn’t the only relationship Herrod leveraged for this project. To guarantee the engine’s internals could endure the huge forces they would face, Herrod asked JE Pistons in California to create a custom lighter forged piston with special skirt coatings to complement H-beam conrods.

While Herrod understandably keeps the piston specs a secret, he has gone further to stamp exclusivity into these parts. Literally. Every DJ LE’s unique VIN and build number are etched into each conrod and piston, as well as the billet oil-pump gears that, working with a Shelby Mustang GT350 sump baffle, keep everything oiled under hard use.

Then there was Ford Australia’s serendipitous involvement. Herrod informed CEO Kay Hart of the DJ LE project. And as a gesture of good faith Ford Oz was able to divert 30 Mustangs from the production line for the cause – meaning Herrod knew the VIN numbers he needed to give his suppliers when ordering batches of parts.

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Even the Kooks headers bear the unique tags. As well as that, they are also tweaked to guide exhaust gases into a Borla three-inch exhaust system and what Herrod calls a ‘green cat’. He says the cat has “a special substrate that’s very expensive, but it will handle the power and keep the emissions right”. In fact, it will handle as much as 1000 horsepower.

And that’s just as well, because the upgraded rotating assemblies in the stock third-generation Coyote V8 let Herrod electronically bump its rpm limit to 7800rpm. This higher heart rate helps it grunt out 949Nm at 4850rpm and 635kW at 7800rpm. Or just over 850 horsepower. In a Mustang. Gulp.

Dick Johnson drives Mustang Supercar in Adelaide

Of course, while these figures are angry enough to make The Hulk seem well adjusted, Herrod had to ensure the DJ LE could keep its cool. To do this, he sourced a larger transmission oil cooler that’s 35 per cent more efficient than standard. And for good measure he also ordered a larger aluminium radiator and added the R-Spec’s thermostatically controlled rear diff cooler (as per a Shelby Mustang GT350).

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While you might think this much power would snap the car’s driveline like chopsticks, it’s surprising to hear Herrod only needed to replace the half-shafts, with beefier Ford-built items. A 4kg-lighter carbonfibre tailshaft was also installed to smooth out NVH, because if the DJR 320 proved anything, it’s that Johnson and Herrod believe a road car should be able to handle day-to-day duties with ease.

For that reason, Herrod tweaked out any vibration in the exhaust system, while installing the standard Mustang’s bi-modal flaps in the Borla rear exhaust canisters. Custom engine and transmission tunes also help, not only to optimise the engine’s power but to calm a 10-speed automatic grappling with almost twice the urge of a standard Mustang.

Dick Johnson's Tru Blu Falcon to ride again

Herrod admits the grunt can magnify the transmission and stability control’s inherent problems, which is why he recommends driving with as little assistance as possible – in manual mode and with stability control switched off, if you’re brave enough.

Otherwise, buyers can opt for the six-speed manual, which scores a short-throw shifter.

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Herrod’s philosophy extends to under the car as well, where lowered springs front and rear are stiffer but progressive, for more control. Adjustable swaybars are fitted at both ends, and Herrod secured a custom tune for the Vehicle Dynamics Module through Ford Performance. It’s programmed to ride “just like R-Spec”. Which is excellent.

No automatic sequel to R-Spec planned, says Herrod

At all corners are Forgestar wheels that span 20 inches in diameter. They are 9.5 inches wide up front and 11 inches out back to fill out 275mm- and 305mm-wide Michelin Pilot Sport 4S tyres respectively.

Enormous brakes complement the new grip levels, with GT350-spec Brembo calipers front and rear dwarfing the original system’s components.

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A lowered ride height broadens the DJ LE’s stance with the help of unique horizontal front winglets, as well as a new moulded front lip that matches the existing plastic grain. There’s also a custom sticker pack that, with the blanked-out front grilles, add a hint of menace.

But it’s the wing and roll-cage that really set the whole thing off. The spoiler looks awfully like the Shelby Mustang GT500’s, but Herrod assures us it’s a unique Herrod Performance/Ford Performance product. Either way, it’s gorgeous and matches the optional bolt-in roll-cage nicely.

Yes, like a 911 GT3, the DJ LE offers a half-cage. Watson Racing, who make Ford’s Cobra Jet dragsters, built it to Herrod Performance’s custom right-hand drive specifications, and Herrod has invested thousands for CAMS approval. It even deletes the rear seats, replaced by a specialised cover.

A few final touches really ram home the DJ LE’s special nature. The factory Recaro seats are upholstered in new Italian leather and bear the rear exterior badge. And if you look closely, their stitching pattern matches the blower’s ribbed lid.

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Then there are the puddle lamps that cast ‘Dick Johnson Limited Edition’ on the ground when you open the door (which reveal scuff plates bearing the same title). It’s like the red-carpet VIP treatment, which is the sort of level Herrod Performance has reached after earning tier-one supplier status through the work on R-Spec. That also opened the doors to other outfits just like it – something Herrod again leveraged for the finishing touches.

First DJ LE Mustang auctioned

“When you look at the badging on the front fenders,” he says, “then the shield on the back panel, they’re all proper injection-moulded badges. It was over $10,000 just in tooling to make those badges for 30 cars. It’s no sticker pack car.”

And even though this car bears Dick Johnson’s name, it’s obvious it, in a way, will highlight two individuals’ careers. And Herrod knows that too. “We set out to make some money obviously, but it wasn’t about making a lot of money out of a car, it was about making a car that no one has ever built, so when DJ’s gone and I’m gone, people will still be talking about this crazy Dick Johnson car that Herrods built back in 2020.”

We have a feeling they will.

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Ford Mustang Dick Johnson Limited Edition Specs

Body 2-door, 4-seat coupe
Drive rear-wheel
Engine 5035cc V8, DOHC, 32v, supercharger
Power 635kW @ 7800rpm
Torque 949Nm @ 4850rpm
Power/weight 347kW/tonne
Transmission 6-speed manual (optional 10-speed auto)
Weight 1829kg
Suspension struts, adaptive dampers, coil springs, anti-roll bar (f); multi-links, adaptive dampers, coil springs, anti-roll bar (r)
L/w/h 4789/1916/1367mm
Wheelbase 2720mm
Tracks 1538/1534mm (f/r)
Steering electrically assisted rack-and-pinion
Brakes 394mm drilled/ventilated discs, six-piston
Calipers (f); 378mm drilled/ventilated discs, four-piston calipers (r)
Wheels 20.0 x 9.5-inch (f); 20.0 x 11.0-inch (r)
Tyres 275/35 R20 (f); 305/30 R20 (r); Michelin Pilot Sport 4S
Price $180,000

Four DJLE Engine Details

1. Fuel source

The engine features new timing chain guides to handle the heady rpm it can muster, while each car is ‘tuned exclusively to run on Shell 98 RON V-Power’ - a team sponsor of DJR Team Penske.

2. Pretty thing

The custom billet aluminium lid atop the Whipple is only outdone by the module Herrod specified on the end of it, complete with dash-12 fittings and a place for the car’s unique build number.

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3. Open the taps

The primary injectors are upgraded using what Herrod calls “55-pound-an-hour” items, his instinct to speak in imperial revealing an immersion in the American auto industry.

4. Big mouth

Fore of the supercharger sits a 132mm throttle body, itself at the end of what Herrod calls a “monstrous” air intake. Obviously, with the DJ LE road legal and engineered, the filter is hidden away.

DJR 320: The hotted up Falcon

After a failed hotted-up six-cylinder EA Falcon followed Johnson’s aborted XE Falcon project in the ’80s, the DJR 320 was a fully sorted effort from the get-go.

Backing up its name was a 5.4-litre DOHC V8 for which tuning partner Rob Herrod developed unique cam profiles to bump power to 320kW at 5300rpm and torque to 540Nm at 4000rpm. And the story goes that there was more in it, if only Herrod could crack the ECU to raise the rpm.

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Transmission options were a five-speed manual and four-speed auto.

It also scored gorgeous Y-spoke 19s, special Dunlop rubber and suspension personally developed by Dick Johnson himself.

Priced handsomely at $90K to clear FPV’s own GT and F6 products, it scored a reworked interior and exterior to suit. But in the end that might have been why only 25 were made.