Words: Harrison Wade Photos: Isaac Western
When Jason Adams rocked up to his family home with a dilapidated 1969 Holden Monaro GTS in tow, we can only imagine the look on his wife’s face, considering she thought she was getting a “great Mother’s Day present”. After all, it’s easier to ask for forgiveness than it is to get permission. He was quick to explain that this would be a simple project that he could tinker away at for a few months and turn it into the perfect Sunday cruiser. But like all good builds, things soon snowballed.
Six years later, ‘The Rust Bucket’, as his wife used to call it, has been reborn as a 1,500hp+ twin-turbo 427ci LS-equipped weapon of an HK, aptly named ‘PRO HK’, which pays tribute to Jason’s childhood love affair with the Monaro back when it dominated Bathurst. “Having watched some early Holden vs Ford Bathurst races, you can’t get any better than the 1968 Bathurst win with the Holden HK 327 GTS taking out first, second, third, and fourth,” he says. For a kid who grew up with that on the tele, it was almost certain that he’d end up owning one someday. “I had been looking for years for an HK as they very rarely pop up for sale,” he explains. “I thought it would be pretty cool to get one of the very first factory Holden V8s.”
The example Jason ended up with was far from perfect, as it was just a rolling shell with the “usual factory Holden rust”, as his Ford-loving mate calls it. His original plans for the car included a cammed V8 and a tidy-up of the bodywork, which soon escalated when another mate, Dan, ran a tape measure over the engine bay of his newly acquired ’67 Chevelle project. The pair found that the dimensions came back surprisingly close to the HK’s, which ended up being as good a reason for Jason to make a phone call to Tom Nelson at Nelson Race Engines (NRE) over in the United States — the same company that built the insane bare metal 2,200hp+ ’68 Hemi Charger ‘Maximus’ featured in the blockbuster Furious 7 film. With that, Jason’s build went from a street-friendly cruiser to a show-spec streeter with a twin-turbo LS package.
The engine that arrived from Nelson Race Engines is nothing short of a beast, and a far cry from the factory Monaro GTS’s 327ci Holden V8, which made a fractional 250hp. Built around a Dart billet block with a 4340 crankshaft (4.0-inch stroke), BoostLine I-beam rods, and forged JE 8.8:1 pistons, the bottom end is designed to thrive under serious boost. Up top, each cylinder is fed by Dart Pro 1 280 LS3 heads with six bolts per cylinder to ensure they stay stuck down, while the valvetrain consists of Comp Cams Shaft Mount rocker arms, a custom NRE hydraulic roller cam running GM Racing roller lifters, and inconel exhaust valves.
As for the party pieces, air is charged by a pair of NRE 72mm mirror-image Gen2 billet turbos and cooled by a custom PWR 81mm tube-and-fin intercooler. It then enters the motor through a Shaun’s Custom Alloy fully billet alloy intake manifold and 90mm drive-by-wire throttle body. Charge air is regulated by a set of 46mm Precision wastegates and TiAL blow-off valves. Each turbo sits on its own NRE stainless 304 TIG-welded header before spent fuel and air are ejected through three-inch collectors into four-inch pipes coated in HPC Hipercoat Extreme Coating, producing quite the noise as it does so. Fuel delivery falls to an Aeromotive Trifekta setup, consisting of, not one, not two, but three 450LPH Walbro pumps, with eight 1,500cc Black Ops injectors, and a 100-litre height-extended factory HK fuel tank. Engine management is taken care of by a Holley Terminator Max ECU, tuned to a whopping 1,500+ horsepower on race fuel, and 1,220hp on 98 octane.
With an engine of this calibre running in such a confined space, cooling is of utmost importance, which is why Jason opted for a PWR 68mm VFIN radiator. To ensure it fit, he had the team at Waiuku Radiators alter the inlets and outlets, allowing the billet Meziere Electric Water Pump (LS Race Series unit) to push an obscene 208 litres of coolant through the system every minute. Aeroflow fittings plumb the cooling and fuel systems throughout.
Now all that was left to do was shoehorn the donk into its final resting place — a task that proved to be a bit more difficult than previously thought. While the initial measurements of the HK’s engine bay showed that the engine would fit, this wasn’t the case in actuality. Measure once, cut twice, right? “HKs definitely weren’t designed to fit a 427ci with twin turbos under the hood,” Jason says. “There was a lot of head scratching and custom fabrication work to get it to fit.” At this point, Jason called in the expertise of Luke from Franklin Speed Shop, who worked his magic on the bonnet by notching the bracing to clear the billet intake, smoothing the engine bay, and tubbing the front arches.
With the reassurance that the engine would fit, Luke made the call to strengthen the centre section of the chassis to accommodate the vast increase in power. To do so, he laddered four chassis rails together, with two being hidden within the factory sills, while the front and rear clips were left stock, as much as Luke tried to convince Jason to beef them up. The rear tubs were then fabricated, followed by the internal structure being reinforced, and a custom transmission tunnel built to suit the new driveline. Attention was then turned to the body, with the quarter panels and doors being replaced with new parts from Rarespares, meaning the only original panel left was the roof. Luke then worked through the internal seams before stitching the quarters back on and sending the shell off for a final blast before paint. That brings us to the final finish: House of Kolor Tangelo Pearl, which Jason entrusted the team at Antonievich Restoration to lay on after perfecting the panel gaps, skimming, blocking, and priming the whole car.
After the HK came back from paint, it was time to start putting everything back together, starting with the suspension to get the car rolling. Up front, you’ll find a set of QA1 adjustable coilovers, joined by a set of Motofab roller bearing parabolic mono leaf springs with adjustable traction bars out back, and Strange shocks all around — a setup with proven credentials in seven-second drag cars in Australia. The engine and gearbox were then shoehorned into the car for the final time, the latter being an NRE-built Tremec Magnum six-speed manual unit, backed by an aluminium flywheel, McLeod Twin Disc Clutch, and a Quick Time Scattershield. A driveshaft from Driveshaft Specialists bridges the gap to the Krysler Shop-built custom nine-inch rear end, housing an S-Trac limited-slip differential, an HD Pro aluminium through-bolt gear case, and Strange 35-spline axles. “Tim from the Krysler Shop sorted that out, and it definitely doesn’t disappoint. It squats the rear and gets good traction,” Jason tells us.
Braking is all Wilwood: slotted discs and six-piston callipers at both ends, with a Hydroboost booster setup. The HK is set off by a set of polished Intro Wheels Vista, measuring 18×7- and 20×10-inches with 225/35R18 and 275/30R20 Pirelli rubber front and back, respectively. Each wheel is held in by five-eighths wheel studs.
Now for the most important bit, the place where Jason will spend most of his time with the car — the interior. Jason wanted to retain as much of the car’s original character as possible by restoring only what needed to be done, such as the upholstery, which was given a complete refresh thanks to Winner Products, with the only items you won’t find in a factory being the billet shifter and a Dakota Digital speedometer conversion to handle modern speed signals. After a wire-up by Paul at Waiuku Auto Hub and new glass installed by Chris at Counties Auto Glass, it was finally time to hit the road.
Having spent four long years building the car, the result is just what Jason expected — a somewhat unassuming piece of Aussie muscle history that, when you open the bonnet, leaves people in awe. “There’s definitely been a few good reactions when you pop the bonnet,” Jason says, and you can imagine that’s somewhat of an understatement. As for the driving experience? “Insane. It definitely gets the heart beating when the boost kicks in.” We asked Jason what his plans for the car are now that it’s complete, to which he told us that his only intention is to use it as a weekend cruiser, similar to what his wife must’ve first imagined when it first showed up on the back of a trailer. Only now, it may get a few noise complaints from the neighbours when firing it up on a Sunday morning. Some Mother’s Day present, eh?
OWNER Q&A
DRIVER: Jason Adams
PREVIOUSLY OWNED CARS: Holden EH Wagon, HK Premier and Monaro, many Commodores, including VR, VX, VY Wagon and Clubsport Sedan, VE R8 Clubsport, and a Holden VF R8 & GTS & GTS-R
DREAM CAR: Holden GTS-R
WHY THE HK? First iconic factory Holden with a V8, and it’s a coupe
BUILD TIME: Four long years
LENGTH OF OWNERSHIP: Six years
JASON THANKS: Luke at Franklin Speed Shop for the chassis and panel work, Johny at Antonievich Restoration for the paint, Chris at Counties Auto Glass for the windows, Paul at Waiuku Auto Hub for the wiring, Tim from The Krysler Shop for the diff and suspension, the team at Waiuku Radiators for the radiator, and my wife and kids for putting up with it
SPEC LIST
VEHICLE: 1969 Holden Monaro GTS (HK)
ENGINE: Nelson Racing Engines twin-turbo 427ci LS, Dart billet block, 4.0-inch stroke 4340 crankshaft, Boostline I-beam rods, forged 8.8:1 JE pistons, Dart Pro 1 280 LS3 cylinder heads, inconel exhaust valves, six head bolts per cylinder, custom NRE hydraulic roller cam, GM Racing roller lifters, Comp Cams Shaft Mount rocker arms, Shaun’s Custom Alloy intake manifold, 90mm drive-by-wire throttle body, custom PWR 81mm tube-and-fin intercooler, twin NRE 72mm mirror-image Gen2 billet turbos, twin 46mm Precision wastegates and TiAL blow-off valves, NRE stainless 304 TIG-welded headers, HPC coated twin three-to-four-inch exhaust, Aeromotive Trifekta triple 450LPH Walbro fuel pumps with filters, connectors, and regulator, ⅝-inch fuel line, ½–inch return line, 8×1,500cc Black Ops injectors, 100-litre height-extended factory HK fuel tank, Holley Terminator Max ECU, custom PWR 68mm VFIN radiator, Meziere LS Billet Race Series (55 gallons per minute) Electric Water Pump, Aeroflow fittings throughout
DRIVELINE: NRE-built Tremec Magnum six-speed manual, aluminium flywheel, McLeod Twin Disc Clutch, Quick Time Scattershield, Driveshaft Specialists driveshaft, Krysler Shop custom nine-inch rear end, S-Trac LSD, Strange 35-spline axles, HD Pro aluminium through-bolt gear case, five-eighths wheel studs
SUSPENSION: QA1 coilovers, Motofab parabolic mono leaf springs, adjustable traction bars, Strange shocks
BRAKES: Hydroboost booster, Wilwood slotted discs, Wilwood six-piston callipers
WHEELS/TYRES: 18×7-inch and 20×10-inch Intro Wheels Vista Exposed wheels, 225/35R18 and 275/30R20 Pirelli tyres
EXTERIOR: House of Kolor Tangelo Pearl
INTERIOR: Winner Products upholstery, factory steering wheel, billet shifter, factory restored gauges, Dakota Digital speedometer conversion
PERFORMANCE: 1,500 horsepower on race fuel, 1,220hp on 98 octane
