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598-cube 1969 Holden HT Premier

By Carly Dale | Photos: Chris Thorogood, 02 Jul 2019 Features

598-cube 1969 Holden HT Premier

Young gun Nick Piotto proves that cubes are king with this street-legal, 1000hp Holden HT Premier

I'M LOVING the current movement of shoehorning crazy horsepower into a factory-appearing car, backed by mega-fat rears – all while being 100 per cent street-legal. And Nick Piotto’s ’69 HT Premier is a textbook example, with factory integrity coupled with an off-tap 598ci big-block Chev stuffed between the rails and backed by 12-inch rear wheels – it’s a look that’ll forever be tough.

This article was first published in the June 2019 issue of Street Machine

Holden HT PremierBack in 2012, 20-year-old Nick locally sourced a bog-stock Sea Mist Green HT Prem, with a freshly built 186-cuber and three-on-the-tree. “The body was nice enough, so I was going to leave it stock,” Nick says. “I also have an HK Prem which is rougher, so I was going to modify that.” Only a few months later a blown clutch in the HT was the rather minor catalyst for the car’s transformation into the now robust powerhouse laid before you. “I had to pull the gearbox out anyway, so I figured that I may as well do up the HT,” Nick explains. “The plan was to have the car looking as original as possible other than the big wheels and scoop.”

Read next: Blown big-block 1970 Holden HT Monaro GTS - 1FATHT

Holden HT Premier rearA white-roofed Sea Mist Green Prem is so wonderfully grandpa-spec, which makes the massive scoop and stomper rubber so much cooler. Then pop the bonnet and you’re in for a treat of mega-cube goodness neatly tucked into a pristine ’bay

Nick started out with thoughts of a small-block Chevy up front and mini-tubs out back, but it didn’t take him long to change his mind, thanks to a friendly antagonist and a relative bargain in the tub department – we’ll get to that a bit later.

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Holden HT Premier side“I had bought a cheap ’glass reverse-cowl off eBay, but it was very average,” says Nick. “Ed from SA Chassis Service said that after two launches it’ll be all warped, so he suggested a steel scoop. My cousin had one for his AP6 Valiant, so I bought that and had it fitted up. The engineer was really happy with it too”

“After a bloke at work got into my ear about big-blocks and their ability to produce large horsepower with lower revs, I reckoned that sounded good,” Nick says. “So I went for as many cubes as I could while still keeping it low-deck for fitment.”

Read next: Supercharged LS-powered 1970 HT Holden Kingswood 

Holden HT Premier rearNick scanned the Shafiroff website and was taken with the offerings from the well-known maker of behemoth donks, and a few months later a 1002hp, 598-cube Chev landed in Australia.

Topping the monster is a 1150cfm Dominator carby with Brodix manifold and heads. The cam is a custom-spec Shafiroff hydraulic unit, while further below are Manley H-beam conrods and crank. Off-the-shelf 2¼-inch Castle headers feed the pollution into 3½-inch pipes. To keep it streetable, the massive 9.8-litre donk guzzles PULP, fed by a MagnaFuel pump and sparked by an MSD ignition.

Holden HT Premier wheelsThe 15in Center Line Adelaide hubcaps were always part of the plan; it’s only the rubber that grew. “The 29in-tall tyres counteract the 4.11 gears,” Nick reckons. “I was going to run 3.9s but upped to 4.11s once I added the full tubs. And I’m so glad that I went with full tubs, as the big tyres change the look of the car. It really stands out”

Everything about the set-up is oversized, yet Nick reckons that the fat-block wasn’t overly difficult to fit. “We cut and lowered the front crossmember to drop the motor a little,” he explains. “The big- and small-blocks use the same engine mounts; it’s just that the big-blocks are longer at the front, so I used a short electric water pump to clear the thermos.” Other than that, there was a minor extractor modification required once the dummy block was replaced with the star attraction.

Holden HT Premier bootAs for the tubbing upgrade, Nick was once again easily swayed. “Ed from SA Chassis Service explained that mini-tubs would allow for about 30mm extra tyre width and height, but for a little more money he’d do a full tub – then I could put some serious rubber on there. It doesn’t take much to convince me, so I was like: ‘Yup, done!’” Nick laughs.

Holden HT Premier engine bay“The 598ci fits like a 454ci, whereas the 632ci have tall-deck blocks so the heads can stick out of the bonnet line,” Nick says. “I used a dummy big-block with off-the-shelf extractors and everything fitted really well. But when I fitted up the real motor the extractors went out by about 10mm and fouled. So Dream Works Garage shaved the steering box and I had two header pipes modified”

SA Chassis Service also strengthened the crapola out of the chassis and added new rear rails to suit the widened tub infrastructure, before giving the toughened HT a fresh lick of Sea Mist Green topped with the Premier’s trademark ivory roof.

Holden HT Premier engine bay“The dyno sheet is for 1002hp, but I don’t know if that’s a true reading or not; it was dynoed in America, so maybe it’s only really 500hp, but it feels fast,” Nick laughs

Inside, HT-spec Isis Green vinyl from Winner Products covers all the right furnishings, thanks to Monaco Auto Trimmers. It’s only the Auto Meter gauges and B&M Quicksilver shifter that deviate from the ’69’s heritage.

The finished product offers a stout look that won’t easily date. Which is a good thing, as it meant the HT never went off-trend during the six years of building, so when it eventually hit the Adelaide streets in December 2018 it was still crispy-fresh.

Holden HT Premier interiorNew Isis Green vinyl covers all expected surfaces, producing a minty factory-fresh trim. “I couldn’t believe that they reproduced the colour; it’s very close to original,” Nick says. The only deviations from stock in here are Nick’s preferred B&M shifter and Auto Meter gauges

“There are a few cosmetic touches to finish off, such as some re-chroming, painting the badges and adding mouldings – and I kept the 186 badges to confuse people,” Nick laughs.

“I’m glad that I modified the HT instead of my HK, as I feel that they look better done up and with big wheels; I prefer HKs as stockers,” he continues.

“My HT doesn’t have a showroom finish; it was always built to be driven. Only a few weeks after getting it on the road I had put a scratch on the door,” Nick admits, shrugging. “I do drive it a fair bit, as big-blocks are so good for cruising, but when I put my foot down the power is right there – that’s what I love about biggies.”

Holden HT Premier rear seatNick’s keen to run a number on the track, too. “Running it at the drags is the best proof of horsepower; it’s about a big trap speed and a quick time,” he says.

“Although AIR has shut down at the moment and there’s rumours that it may not even re-open. So, I’d love to race The Bend’s drag track as soon as it’s running; I’m hoping that it’ll run nines over the quarter in full street trim.”

Go the big-block!

Holden HT Premier dash100% STREET DRIVEN

“IF YOU do the right thing then you can get cars like this engineered in SA,” Nick says. “Matt Morgillo (SM, Feb ’19) is a mate of mine and his HQ Statesman is also all legal.

“I used Sot from Speed Garage & MVE for the engineering. Sot asked me what I wanted to do and then let me know what needed to be done. I did all of the groundwork before I’d bought the motor so I went down the right path. Sot was there as I needed throughout the whole build. I just followed what he said and did everything right.

“I would’ve passed inspection the first time, but I forgot to bring the jack and wheel brace to remove my own tyre!”

Holden HT Premier onroadNICK PIOTTO
1969 HT PREMIER

Paint: Sea Mist Green, white roof

ENGINE
Brand: Shafiroff-built Dart 598ci Chev big-block
Induction: 1150cfm Dominator carby
Manifold: Brodix
Heads: Brodix
Camshaft: Shafiroff custom hydraulic
Conrods: Manley H-beam
Pistons: Shafiroff
Crank: Manley
Oil pump: Moroso, High Energy sump
Fuel System: MagnaFuel pump, PULP
Cooling: Custom four-core radiation with twin thermos
Exhaust: 2¼in Castle headers into 3½in system
Ignition: MSD

DRIVELINE
Trans: Coan Racing TH400, full-manual, reverse-pattern
Converter: Dominator 4000rpm stall
Diff: 9in, Detroit Locker, full-floater, 4.11:1 gears, Strange 35-spline axles

SUSPENSION & BRAKES
Front: HT Holden V8 springs, Pedders 90/10 shocks
Rear: HT leaf springs, Pedders 50/50 shocks
Brakes: Wilwood disc and calipers (f & r)
Master cylinder: Wilwood

WHEELS & TYRES
Rims: Center Line Auto Drag; 15x5 (f), 15x12 (r)
Rubber: Mickey Thompson Sportsman SR; 26x6 (f), 29x15 (r)

THANKS
SA Chassis Service for the tubbing, chassis work, body and paint; Monaco Auto Trimmers; Dream Works Garage for the mechanical; Sot from Speed Garage & MVE for the engineering