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565-cube big-block Holden HZ ute

By Tas McMillan, 25 Aug 2020 Features

565-cube big-block Holden HZ ute

After Matt Milnes got out of racing boats, he had to find a new home for his 960hp big-block Chev

THIS eye-popping, tyre-shredding HZ ute is an amalgamation of two cars and a ski race boat, with a healthy dollop of shoebox Chev in there too. You see, Matt Milnes used to be into water ski racing, but he decided to give the sport the flick when his kids came on the scene, and that left him with a brutal big-block gathering dust in the shed.

This article was first published in the August 2020 issue of Street Machine

Holden HZ ute

The original dream was to fit the engine to his long-term project, a ’57 Chevrolet two-door, but the amount of work required to get the Chev up to scratch was daunting. Instead, Matt opted for a quicker build and picked up the HZ as a roller, handing it and his race engine to the late Craig Brewer of Pro Pipes with a brief to make the two into one. With the big-block ute ready to run, it headed back to Matt’s shed and a date with destiny.

Read next: 615-cube big-block 1974 Holden HQ ute

Holden HZ ute side

“One day I was standing out the front of my garage, leaning on the tailgate of the ute, when I spotted a horse running up the road,” Matt says. “When it got to my property it saw me and decided to run up the driveway and straight at me! I jumped out of the way, but it hit the tailgate and went over the ute. The horse got stuck between the garage wall and the ute, so it kicked the shit out of the whole side of the car.”

Read next: Show-stopping blown big-block Holden HJ burnout ute

After a vet managed to convince the horse to settle down, the ute was pushed out of the way so Matt could survey the damage. Needless to say, the debate over whether to do a rotisserie rebuild was settled then and there.

Holden HZ ute rear

The ute may wear the number plate ERUPTN, but it’s not the first of Matt’s machines to carry a volcanic name. “The ski boat was called Eruption, so I bought the plates for the tow car I had at the time, and I’ve just hung on to them,” he says

“It had a blown small-block in it before I bought it and it was a reasonably clean car, but when we blasted it the rust was horrific,” Matt says. He eventually found a solution in the form of an almost rust-free WB six-cylinder with just 115,000 kays on the clock. The new ute was stripped back and all the good bits from the HZ were bolted on before Paul from JPS Automotive doused it in Interceptor Yellow with a splash of white pearl over the top.

Read next: 434-cube 1971 Holden HQ ute

Holden HZ ute front

Matt’s old boat, Eruption, wasn’t going to be powered by any old Chev truck engine, so the big-block is something pretty special. “It originally had an eight-litre engine; then I moved to a ProCharged big-block about 15 years ago, but I got sick of breaking belts all the time,” Matt says. “I thought I’d build a killer Unlimited-class aspirated big-block, so my engine builder Matt Vandersluys got onto Taylor at Texas Race Engines. They built the engine and the manifold for it.”

Holden HZ ute tray

While the ute’s tray may not look like it copped a whole lot of work, the devil’s definitely in the detail. The wheel tubs were widened 120mm each to allow for the 295s while retaining the standard design, and the fuel cell is a work of art. “The tank is 130L and it doesn’t last very long,” Matt says. “My friend Aaron Matthews folded it all out of aluminium; I’d hate to think how many hours are in it”

The swept volume of the aluminium Merlin block totals a monstrous 565 cubes, with heavily worked aluminium Oldsmobile oval-port heads and that impressive sheet-metal TRE tunnel-ram on top. Inside the block, a Lunati crank wears Oliver rods and Bill Miller pistons, and a lumpy Bullet cam sends signals through Crower lifters, Manton pushrods and Victor valves. Gone are the dual carbs and avgas of Matt’s boat racing days; in their place is a sweet EFI system and pump 98 that allows for much more street-friendly power delivery.

Holden HZ ute underside

The Baer six-pot calipers on the front end clamp dinnerplate-sized 365mm rotors, while the 15x10 rear rims wear Wilwood 240mm discs with four-pot calipers, making the ute much more planted on the road

Don’t think the swap to boring old 98-octane has mellowed this monster motor much – how does 737hp at the rubber grab you? “Jason Ghiller from Tunnel Vision tuned it,” says Matt. “He said it’s the most powerful NA engine that’s been on his dyno, and it was about 40 degrees, too!”

Holden HZ ute engine bay

After the debacle with the shell, Matt had the team at All Race Fabrications treat the chassis to a birthday as well. The old Holden copped some serious reinforcement to match the power increase, along with a modern rack-and-pinion front end, a triangulated four-link and the super-subtle wheel tub stretch. Matt called on Graeme Angus, an ex-Holden engineer and race-car brake designer, to address the HZ’s stopping gear. Graeme put together a package consisting of Baer six-piston front disc brakes and a Hydro-Boost system that runs off an electric Astra power steering pump tucked into the driver’s-side front guard.

Holden HZ ute engine bay

In order to make the monster big-block more street-friendly, the twin avgas carbies were swapped for a pair of Accufab throttlebodies and an octet of injectors, and the massive bumpstick was ditched in favour of one almost-as-enormous Bullet item

Inside, the dash and tiller are genuine GTS items, and the race seats were retrimmed in matching GTS fabric. The engine’s vital stats are displayed on the FuelTech FT600 combination dash/ECU, and the rollcage is there to keep Matt safe if the ride ever gets a bit too wild.

Holden HZ ute interior

Matt’s kept things relatively traditional inside, highlighted by a genuine GTS dash and steering wheel. The Cobra race seats have been trimmed in GTS fabric to match. Modern additions include the rollcage and FuelTech FT600 digital dash/ECU

“The torque’s frickin’ huge,” laughs Matt. “On the street it wheelspins everywhere; it’s really aggressive off the line and it just hauls in second. We want to road-tune it a bit more and Jason wants to add more timing, but it’s pretty much finished. I reckon I’ve had 20 utes, from HQs to Maloos, but this was my first proper build and is my dream car.”

You couldn’t ask for a better result!

Holden HZ ute dash

NEXT!

WITH the HZ finished and the ’57 two-door still requiring lots of love, Matt’s now working on what he calls his COVID-19 project: a legit VH Group 3. “It’s one of 13 VHs with a VC bodykit, and was written off at 40,000km,” he says. “A panel beater bought it to restore to concours condition, but sadly, he died before finishing it. I picked it up as a roller with all the parts in boxes, and Paul at JPS rebuilt it for me.”

The VH came with a pretty angry 560hp Holden stroker, but that wasn’t enough for Matt, so he’s chucked the iron lion in favour of easy LSA power. “It’ll have a TH400, mini-tubs, a fabricated diff and 275s, and I’m chasing 1000hp. Hopefully it’ll make a good Drag Challenge car!”

Matt Milnes

MATT MILNES
HOLDEN HZ UTE

Paint: Interceptor Yellow

ENGINE
Block: World Merlin aluminium
Capacity: 565ci
ECU: FuelTech FT600
Induction: Twin Accufab throttlebodies
Manifold: TRE sheet-metal
Heads: Oldsmobile aluminium
Camshaft: Bullet
Springs: PSI
Rockers: Jesel
Pistons: Bill Miller
Conrods: Oliver
Crank: Lunati
Sump: ASR
Exhaust: Custom 2in primary extractors, twin 3.5in, Hooker mufflers
Ignition: ICE
Cooling: Race Radiators

TRANSMISSION
Gearbox: Powerglide
Converter: SDE 4500rpm
Diff: Fabricated 9in, 3.7:1 gears, Truetrac

SUSPENSION & BRAKES
Front: Gazzard Brothers springs and shocks
Rear: Gazzard Brothers springs, shocks and anti-roll bar
Brakes: Baer 365mm discs and six-pot calipers (f), Wilwood 240mm discs and four-pot calipers (r)

WHEELS & TYRES
Rims: Billet Specialties; 18x5 (f), 15x10 (r)
Rubber: M/T Sportsman SR 26x6 (f), M/T ET Street 295/55R15 (r)

THANKS
Paul & Joe at JPS Automotive; Matt Vandersluys at Valley Engines; Marcus and the boys at Speedpro; Pazzo and the boys at All Race; Chris at Race Wires Auto Electrics; Jason at Race Radiators

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