In an era where engines pulled straight out of donor cars can be fitted with bus turbos and fed E85 to make double the factory horsepower, it can be easy to lose sight of where we’ve come from. Edin Dervisevic remembers how things used to be, with his stunning ’68 HK Monaro GTS rocking a naturally aspirated head-kicker of a big-block that produced an utterly bonkers 1098hp at the hubs during the Horsepower Heroes dyno comp at Street Machine Summernats 37. It went on to not just win the Eight-Cylinder Aspirated class but also smash the record for the most powerful aspo mill ever to have braved the ’Nats dyno – although Michael Saad’s Mk1 Ford Capri has just reset that record at ’Nats 38 by running a touch over 1100hp in qualifying.

First published in the February 2026 issue of Street Machine

Don’t go thinking the HK’s some all-out race car, though. “It’s a street car with a lot of power to it,” Edin laughs. “I wanted a street car like the ones I used to see back when I was an apprentice spray painter and we’d take our Geminis through the Cross. These were the cars you drove back in the day.

“I bought the Monaro from Adelaide and it already had a 454 in it,” he recalls. “But after I started driving it, while the rest of the car was good, the power just wasn’t there.”

That’s when a plan was hatched: “The goal was to make over 1000hp at the hubs to take the NA record at Summernats,” Edin says. That might sound easy, but as with any well-sorted car build, the path to dyno glory was anything but straightforward for this HK.

While the HK-T-G GTS Monaros were big news back in the day thanks to their 327ci and 350ci small-block Chev powerplants, Edin knew he’d need an angry rat motor to reach his goal of 1000+ horses, while keeping it civil enough to drive on Sydney roads.

“Joe Sabato from Hume Performance was a childhood friend of mine, and I got him to build me an engine, which I think was the last one he built before he passed away,” Edin begins. “But I wanted more than 1000rwhp at Summernats, so that meant I’d need over 1100hp at the engine, so I got onto John Agazzi from VP Racing Fuels, as he’s an old-school mechanic who knows how to make big power with traditional methods.”

John put together a big-inch Chev combining a bunch of high-grade hardware geared towards making bulk power. It’s a simple pushrod engine with a single four-barrel carburettor – no blowers, turbos or nitrous to be seen. But the genius of the combo is the science hidden in the simplicity.

Displacing 632 cubic inches, the tall-deck fatty swings Oliver steel rods on a Bryant crank, with 12.5:1 Gibtec slugs compressing the air/fuel mix. The solid-roller cam is a custom grind by Colin Taylor, working Isky lifters and custom-length Manton pushrods in deep-breathing Brodix SR20 cylinder heads, which wear Victory titanium valves.

Up top, a Plazmaman intake is crowned by a 1250cfm Holley XP Dominator four-barrel carburettor, while the MSD dizzy ignites the fuel supplied by a MagnaFuel 500 pump.

“The engine doesn’t have race parts in it, and we concentrated on making sure it has oil and water all through it, so it’s built for the street,” says Edin. “It can sit in traffic for half an hour, no problem.”
Rounding out the drivetrain, a Turbo 400 auto and bolt-together torque converter from Neal Chance take all the strain from the fat-block, while the rear end now boasts a stout nine-inch. The fabricated housing is filled with a Mark Williams centre, 35-spline axles, and 3.5:1 gears, so it can handle all Edin can throw at it.

With the car set up with the best mechanical hardware, Edin’s attention then turned to the cosmetics. While the HK was already neat, things soon rolled out of control once the plan to take the car to Horsepower Heroes was hatched.

“At the time we built the engine, V Resto Garage said they needed to tidy the car up if I was going to take it to Summernats,” says Edin. “It was just going to be a closed-door respray, as the car was already pretty nice, but it turned out to be a full repaint, along with new carpet, new glass, and all-new trim.”

Frank and Roy at V Resto Garage had to overcome the normal HK Monaro rust and some questionable prior repairs, but this was offset by the fact that the car already came with mini-tubs and chassis connectors. Once the body rectification was complete, the shell was treated to a fresh drenching in bright Glasurit Picardy Red.

With those jobs done, the Monaro was ready to make Horsepower Heroes history at Street Machine Summernats 37. There, the car stomped out that magic 1098rwhp figure during qualifying, before going on to win the class with a 1083hp run in the finals.

Now that the car’s run the numbers, Edin is keen to enjoy the HK with his family – once he’s convinced his kids of the virtues of old-school power. “Trying to get kids into old cars is a challenge, as they like VLs, but I tell them, ‘No plastic stuff!’” he laughs.

Edin improved the HK’s handling with a Rod-Tech rack-and-pinion front end, which also gave him Rod-Tech coil-over struts. Wilwood disc brakes live at all four corners, replacing the HK’s standard – and woeful – single-pot solid front discs and tobacco-tin rear drums. Out back, the leaf pack has been trimmed down to a single mono-leaf and adjustable Strange Engineering shocks to lower the ride height and gain traction

EDIN DERVISEVIC
1968 HOLDEN HK MONARO GTS

THANKS
John Agazzi for the record-breaking engine; Roy and Frank Velardi at V Resto Garage for the panel and paint; Ken Hanna at Hume Performance for the carby tune; Al at Al’s Race Glides for the transmission; my family for their patience while building the car.