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Show-spec custom 350-cube Holden HQ Kingswood wagon

By Glenn Torrens | Photos: Nathan Jacobs, 20 Jul 2018 Features

Show-spec custom 350-cube Holden HQ Kingswood wagon

Grant Mahoney has been driving this car in his head since he was a teenager. Now he's built the real deal

This article on Grant's HQ wagon was originally published in the August 2018 issue of Street Machine magazine

FOR custom car fans, Grant Mahoney’s extensively modified HQ Holden wagon is a welcome blast of fresh air in this era of obsessive nut-and-bolt restos. Not that Grant is totally adverse to restorations: “My previous project was a matching-numbers HX Sandman panel van,” he says. “So I couldn’t stuff around with that too much, could I?” he laughs. “So I figured I’d sell that and get stuck into my dream custom wagon.”

Holden HQ wagon sideFollowing the factory bonnet lines, the subtle scoop rises to 65mm-high at the rear. Other major surgery includes pumped rear guards and those swoopy guard flutes.  The stock filler was deleted and a sedan fuel tank and flip-down number-plate filler fitted. The rear side blinkers have gone too. The front end is smoothed out with a custom-built grille and filled bumper slots

The project started not with a car, but with a pair of HQ guards. “I was staring at the guard flutes on the Sandman and thought I could do better,” says Grant. “I was bored after finishing the HX, so I got some guards and made my own flutes. Then I needed a car to bolt them to!

Related: Family heirloom 1968 Holden HK wagon

“I’d been planning this car for years – it’s all the things I wanted to do when I was 18,” Grant says. “All these ideas have been spinning around; the wagon is almost exactly as I first imagined it.”

Holden HQ wagon rearNeat touches in the rear include Grant-made tinted tail-light lens covers, drop tank cover and deleted rear window winder. Grant also polished all the glass with cerium oxide and a felt rotary pad before assembly.

Grant grew up watching his dad Bryan fix and flick cars that he’d bought at auction, and of course he played around with cars himself too. Then adult stuff took over. “I had company cars, had kids, worked to get us to where we are,” he says. “And now I’m into cars again!”

Related: Procharged LS1-powered Holden HX wagon sleeper

Holden HQ wagon cargoThe rear features chromed cargo strips and is finished in a maroon deep-pile carpe. Grant built a curvy enclosure in the rear to hide the audio gear and fabbed some classy speaker grilles to let the sound out 

The HQ was bought only a couple of years ago for a mere 300 bucks. “It was in a backyard out at Reservoir,” Grant explains. “The family had had it from new and it ended up being used as a parts car. The mum eventually wanted it gone so she could grow more tomatoes. I saw it on Gumtree, thought it deserved a second chance and grabbed it.”

Related: Show-spec Holden HG Kingswood burnout wagon

Holden HQ front“The inner guards were roughed out by a mate who makes barbecues,” says Grant. “Then I made cardboard templates, fixed them into position with Cleco pins and got to work. The gum tree in my front yard copped a hiding – who needs an English wheel!”

The wagon was little more than a bare-bones shell, and Grant set about resurrecting it in his humble two-car garage with glee. After some rusty floorpans were replaced, the body was pulled off the chassis and wire-brushed back to bare metal, strengthened with HZ braces, modified to suit Grant’s airbag plans and coated in satin black.

Related: 355-cube HK Premier 'GTS' wagon 

Holden HQ wagon wheelThe body went up on jack stands and Grant spent more than a few weekends flat on his back so that the undercarriage could be tidied up in a similar manner to the chassis.

To get the extra-low stance he was after, Grant raised the trans tunnel and boot floor. The rear end was mini-tubbed so he could get the rubber sitting just where he wanted it.

Holden HQ engine bayGrant put a huge chunk of time into metal fabrication under the bonnet, including the inner guards, radiator support cover and heater blank-off plate. The battery and washer bottle were banished to the rear, the wiper motor chromed and polished and all unused holes in the firewall filled. The billet bonnet hinges are from Bliss Custom Machining

The fitment of the airbag system was planned with military precision. A cradle supporting the twin air tanks, compressor and electronics drops into the underfloor area. All this airbag gear shares space with the battery, spare wheel and windscreen washer bottle. What if he gets a flat battery, you ask? Grant ran a couple of girthy battery cables to the front and set up a jump point for emergency or maintenance charging.

Holden HQ engine bayThe ZZ4 350 crate motor breathes through an Edelbrock Air-Gap intake and 650 carb, both resplendent in Edelbrock’s EnduraShine finish. “My vision was to have the engine appear to be floating in the bay, with the wiring concealed,” Grant says

Plenty of thought and effort went into the interior, too. The bum-holders are four WB seat frames with the headrests removed, split by a full-length custom centre console. The dash is also WB, although heavily modified and fitted with a carbonfibre-look cluster and Speed Hut gauges.

“The interior colour is buckskin,” Grant says. “Anyone can do black. For the outside I also considered a few colours – green, orange – but I decided on this lovely burgundy. It’s a classic combination that’s sort of inspired by prestige European cars. It’s the colour I had in my head when I was 18.”

Holden HQ front seatsThe HQ’s bluff dash has been replaced with the bones of a WB-series item, running Speed Hut gauges. A nice nod to the past is the retention of the 70s-era electric window switches – they look so much cooler than billet ones – and the shifter is a B&M

Grant is proud of the fact he did most of the work at home, modifying and prepping the body to the stage where it was ready for a final block-down and paint, those two tasks taken on by Adam at Hi-Gloss Bodyworks in Knoxfield using DeBeer paint in that lovely Merlot Pearl Metallic.

Just about the only other task he farmed out was some trim work to Croydon Motor Trimming. “I can’t sew a stitch,” Grant admits.

Holden HQ rear seatsThe wagon runs four WB Stato-based bucket seats and is registered as a four-seater. The full-length console houses cup holders and power window buttons

The driveline is pretty simple. Up front is a detailed-to-the-max Chev crate motor that runs to a TH400 auto and a nine-inch diff with 3.25 cogs and a Truetrac limited-slip centre.

The sensational HQ wagon has racked up 3500 kays since it was finished last summer, doing exactly what Grant built it to do: cruise. “Why would you build a cool car and then not be able to drive it?” he reasons. “It keeps me off the street and out of trouble. And the wife always knows where I am!”

Holden HQ dash

PANEL SHOW

Grant's previous project was an awesome Sandman panel van (below) that he restored. “I redid that one from scratch,” he says. “It was a blitz of a project – 11 months and 22 days from beginning to registration, and that included about five months getting painted! It was a full chassis-off, ground-up rebuild. When I get into building a car, I’m possessed!”

Holden panelvanThe Papaya-painted, 308/four-speed Sandman won third overall at the Victorian State Van Titles, and it has scored well with its new owner too.

Sold to free up space and funds for the HQ wagon project, the cool pano now lives in Newcastle – an appropriate home given the beachside port city’s surfie heritage.

GRANT MAHONEY
1972 HQ HOLDEN KINGSWOOD WAGON

Paint: DeBeer Merlot Pearl

ENGINE
Brand: 350ci Chevrolet V8 ZZ4 crate motor
Induction: Edelbrock 650 carb on Edelbrock Air Gap intake
Heads: Alloy
Exhaust: HPC-coated extractors and 2.5in system
Ignition: GM/Chev HEI

TRANSMISSION
Gearbox: TH400
Converter: Pro Converter 3000rpm
Diff: 9in, 3.25:1 gears, Truetrac centre

SUSPENSION & BRAKES
Front: AccuAir airbags, Koni shocks, drop spindles
Rear: AccuAir airbags, Koni shocks, modified floor
Brakes: HQ discs and calipers (f), VR/VS discs and calipers (r)

WHEELS & TYRES
Rims: Intro V-Rod; 17x8 (f), 17x10 (r)
Rubber: Kumho; 215/50/17 (f), 245/45 (r)