Blown LSX-powered HK GTS Monaro

A perfect finish and blown LSX376 grunt define Tim Martenstyn’s ultimate HK GTS

Photographers: Chris Thorogood

Tim Martenstyn’s epic blown HK Monaro isn’t his first crack at building his dream machine, as the Werribee bloke explains. “Before this build, I had a blue HK Monaro,” he says. “Every nut and bolt was brand new.”

First published in the April 2023 issue of Street Machine

Tim was on the home stretch with that car before a cancer diagnosis in 2005 threw him a massive curveball. “It broke me mentally and physically, and then in 2007 my marriage ended, which left me no choice but to sell the car,” he says. “I was heartbroken watching it go down the road on the back of the tow truck.”

Soon after, Tim resolved to build another HK GTS, even if it was the last thing he ever did. “Well, after 11 years, here it is!” he laughs.

Tim’s second chance appeared when an HK GTS cropped up on eBay near Brisbane in 2010. “It was a mess, but it had tags and seemed a genuine, honest thing,” he says. “I booked some flights for myself and a couple of good mates and we headed up for a look.”

A deal was reached and Tim got the car back to Victoria, where he got a rude surprise. “One of the major selling points was how great the floor was; well, after getting the body blasted in Thomastown, it was like a sponge – holes everywhere!”

Good mate Rod Coleman got stuck into replacing the floors, tubbing the car to the rails as he went. “Trust me, if it wasn’t a GTS, it would have some serious rubber on the back, but I couldn’t bring myself to cut it up,” Tim admits. That’s not to say the car’s rolling on cheese-cutters; the rears are a 20×10 to gel with the ‘Dub’ look Tim has long been a fan of. “Big wheels, car as low as you can make it – that became my vision,” he explains.

Tim’s cousin, the late Glenn Rulach of Air Ride, supplied self-levelling airbags for all four corners to complete the stance, while Geoff at Street Tech Fabrications modified the front end and knocked up a custom triangulated four-link rear to accommodate them. “Geoff did an awesome job considering there were no plans for this,” Tim enthuses. “It was all one-off and custom-designed. In the beginning, it wasn’t going to be airbagged, but over 11 years you change your mind a bit!”

Frank Padoin from Impressive Panels is another good mate of Tim’s, and he was entrusted with the bodywork and paint. The HK copped a new beaver panel, front quarter sections, spare wheel section, door bottoms and front apron, along with two new front floors.

“There’s probably 2000-plus hours just in body and paint,” Tim says. “There’s a hell of a lot of work there, and it does get appreciated, which is good!” Another 250 hours were poured into repairing and smoothing the underfloor, while the custom lines to the Wilwood disc brakes were all tucked out of sight inside the car, further neatening the undercarriage.

A red GTS interior was locked in from the outset. “Being an HK GTS, it’s pretty rare, so I didn’t want to change the interior too much,” Tim reasons. “I wanted to keep the original dash and interior trim the way it came out, but I obviously pulled it all apart and did new chrome, new woodgrain, and redid all the needles and gauges. A lot of people appreciate that I’ve sort of kept the original theme and updated it as best I can.”

That left Tim with a choice between black and silver on the outside. After a fair bit of agonising, he settled on House of Kolor Shimrin Jet Black, and each panel (and the undercarriage) was flow coated and topped off with Show Klear by Frank.

“It was going to be an SB2.2 small-block Chev,” Tim says of the powerplant. “But being an HK Monaro, being black, and the way it all turned out, I thought going in the supercharged direction with the LS just suited it a lot better.” With that in mind, Tim picked a 6.2-litre, LS3-based LSX376-B15 crate motor.

It’s topped with an 8/71 blower, manifold and low-profile injector hat, all sourced from Joe Blo Speed Shop. “All black, of course, with all black add-ons,” he laughs. A Holley EFI system manages the flow of 98 fuel from 1000cc squirters, pulled up by a pair of Walbro in-tank pumps inside a custom carrier.

Tony Di Biagio and Luke Foley at TDR Race Engines were tasked with fettling the mill, getting it running in-situ just days before Summernats 35 in a huge final effort. The stock LSX bumpstick wasn’t quite grumpy enough for Tim, though, so a new one was slotted in after the ’Nats with the help of Mark at Sass Automotive.

A hub dyno session yielded 697hp with the new cam, running via a manualised ’Glide, 4000rpm converter, and Truetrac nine-incher with 4.11 gears.

All up, the HK was an 11-year build. “I know there are a lot of cars lately where people put them in resto shops and get them done quicker, but I did a lot of work on mine with a good mate, Paul Sutherland,” Tim says. “Over the last three years we did pretty much all the assembly – I wanted to be a bit more hands-on with mine.”

An unveiling at Summernats in early 2021 was the original plan. “But with COVID, I missed that year, and the second year I just barely missed the deadline,” says Tim, who then liaised with head judge Owen Webb in the lead-up to ’Nats 35. “When I got to Summernats, he came over and said, ‘I’ve been waiting to see this one!’”

The HK earned Top Coupe in the ’Nats Elite Hall when the covers were finally pulled off, along with a barrage of positive feedback over the weekend. A top-five Elite and top-five Overall finish at Showcars Melbourne 2023 followed, which qualified the car for a Meguiar’s Superstars invite to this year’s MotorEx. “I plan on doing the rounds at some more shows before hopefully enjoying a well-earned drive in about 12 months,” Tim says.

He’s now got a clean bill of health, too, but as for another project? “Ah, no.”


Paint:House of Kolor Shimrin Jet Black
Type:GM 6.2L LSX376-B15
ECU:Holley Terminator X
Blower:Joe Blo 8/71
Cooling:Race Radiators, twin Spal fans
Exhaust:17/8in extractors, twin 3in system
Diff:9in, Truetrac, 4.11:1 gears, 35-spline axles
Front:Custom Air Ride airbags
Rear:Air Ride ShockWave adjustable
Brakes:Wilwood 300mm discs and four-piston calipers (f & r)
Master cylinder:Wilwood
Rims:Bonspeed; 19×6 (f), 20×10 (r)
Rubber:225/40R19 (f), 285/30R20 (r)

Rod Coleman; Geoff at Street Tech; Glenn Rulach at Air Ride; Frank Padoin at Impressive Panels; Nino at Riverside Motors, Andrew Tribe at WBC; Admir Blaca; La Rock Auto Electrical; George at Laverton Motor Trimmers; Joe Blo; Tony and Luke at TDR; Andrew at Moolap Mufflers; Ryan at Race Coatings; Mark at Sass Automotive; Mike from Noble Customs; my new great friend Paul Sutherland for three years of tireless help assembling the car and prepping it for shows; Dave and Cherie Smith; Sean; Graeme; Jeff; Wes; Gerald; my family Braydon, Alicia, Jaimes and my girlfriend Carla.