First published in the February 2002 issue of Street Machine

Garry Weatherstone’s VT SS Commodore is its twin-turbocharged V8 engine. Sure, there are big wheels, V8 Supercar brakes and a nice skin of paint but that stonking great Holden stroker with a hair dryer hanging off each bank is what really makes this VT SS stand head and shoulders above most others serving street duties.

“I’ve always been a bit of a turbo nut, but the original idea was to try to get 300kW out of it without forcing the aspiration in any way, shape or form,” Garry says. “We looked and looked at it, then thought, well, there was only one other turbo Commodore we knew of at the time so we decided to go that way. As a result, we easily got 300kW out of it and ended up getting a damn sight more!”

The ‘we’ are the smart blokes at Brisbane’s Cragar Performance who were not only responsible for the cutting-edge engine development and high quality installation, but also for tweaking the transmission and brakes to cope with such enormous power.

Now, make sure you’re not eating anything that could get caught in your throat when you read these figures. On Cragar’s Superflow dyno, Garry’s twin-turbo V8 had its lungs stuffed full of 18 pounds of boost and punched out 692hp (516kW) at 5500rpm and 755ft/lbs of torque at 4500rpm. Yeah, that’s one hell of a BIG small block!

Garry’s owned the car since new. It was one of Holden’s first VT SS models made and one of the first sold in Brisbane. Originally it was a bog stock 5.0-litre V8 with an auto transmission, but it didn’t take long for Cragar’s to void the warranty card.

The factory’s 304 cubic inch cast-iron block has been stretched to 355 cubes using Carillo H-beam rods and a Harrop stroker crank. The self-contained under-bonnet breathing apparatus consists of two Garrett T-28 turbines that ram air induction through a pair of Garrett air-to-air intercoolers. These heat exchangers sit directly in front of the four-core engine radiator and factory thermo fans.

The Motec twin throttle-body manifold is a lovely piece of kit which, according to Cragar, is no longer available from Motec. A stereo set of standard-diameter Holden V8 butterflies provide access to a massive plenum chamber which houses a cross-ram V8 Supercar-style inlet set-up complete with eight beautiful trumpets. Bosch 363 injectors supply the Shell Optimax to the combustion process. The beauty of this massive plenum set-up is that the throttle lag normally characteristic of turbocharged engines is virtually non-existent.

Stock heads carry Ferrea turbo-grade valves and a set of Crane hydraulic roller rockers which dance to the tune of a very mild, off-the-shelf 226/230@50-thou hydraulic cam. Compression has been dropped to 7.98:1 using JE dish-top forged pistons and the big Harrop stroker crank swims in an 8.0-litre Cragar custom-made sump.

Cragar also set-up the surge tank and Bosch Motorsport fuel pump combination under the boot floor. The exhaust system starts with twin three-inch pipes which merge into a single four-inch section over the rear suspension, before flaring into a gaping five-inch outlet at the tail.

Engine management is handled by a Motec M48 ECU and Cragar proudly claims that the engine needs no more than 20 degrees of ignition advance even under extreme load. The Motec also provides nine different turbo boost programs via a dial mounted to the dashboard. The lowest setting, which delivers eight pounds of boost, is good for a lazy 600bhp (450kW) and 617ft/lbs. The highest setting at around 18 pounds is only for Moon launches!

If you’re expecting the drivetrain to be just as exotic, get ready to be disappointed. It’s pretty much stock as a rock apart from a 7.25-inch AP twin-plate clutch conservatively rated to handle 680ft/lbs of torque. We say conservatively, because the grippy AP unit handles this engine’s massive torque loadings with ease.

The rear end is stock too, apart from the addition of Nolathane camber adjusters to try to compensate for the big camber change when Garry dumps the clutch and the SS looks as if it’s trying to drag its bum along the ground like a dog with worms.

“That IRS is great piece of kit,” Garry says. “It actually makes the thing really sit down and bite. When you launch in first gear, there’s heaps of traction. A bit of chirping from the tyres, but that’s about it. If we put traction control on it, we’d have bits of diff flying everywhere. It just wouldn’t be able to handle 500kW.

“The VT Commodore weighs almost two tonnes, so to get that moving at the speed we wanted over the quarter mile was virtually impossible, even with turbos or even by supercharging it to the ultimate level. We took it to the track and did low 12s (12.2) with 500kW and a 142mph terminal speed, but I don’t think we’re going to get much more.”

It’s one thing to get close to two tonnes of Commodore up to warp speed and quite another to stop it again. The front brakes are V8 Supercar-grade six-pot AP calipers clamping enormous 355mm ventilated rotors that were originally designed for the all-conquering Nissan GTR Skyline. It was a real squeeze getting them to fit inside the Enkei Enzo 18×8-inch rims, too. Cragar’s had to machine down the caliper mounting bracket to provide enough clearance and even had to radius the outside of the caliper body to make it fit inside the wheel rim, with barely 40-thou clearance.

Front and rear guards were slightly pumped to accommodate the larger wheels and fat 245/40 Yoko rubber. Stevens Smash Repairs also gave it a skin of striking PPG Harlequin paint for that unmistakable changing colour effect in the sun. As a genuine daily driver, this Commodore is as stealth-like as they come. An awesome street machine.

GRENADE LAUNCHER

Using exhaust gases to spin a turbine is a very efficient way of exploiting every last bit of performance potential from an internal combustion engine. The greatest enemy, though, is the heat generated by this process which has caused many race teams and street machiners a lot of heartache (and wallet ache) due to a multitude of melted under-bonnet components and fires.

However, with quality design and installation backed by correct heat insulation, the turbocharged engine has breathtaking performance potential. The most memorable era of turbocharged engine development was undoubtedly Formula One racing in the mid-1980s, where 1.5-litre engines were producing power outputs exceeding 1300hp in qualifying trim! In fact, these awesome qualifying engines were known as ‘hand grenades’ at the time, because they were capable of producing such staggering power outputs for one hot lap before they exploded.

In recent years, aftermarket supercharging has become a more popular option than turbocharging for modified car owners, particularly those looking for the ultimate ‘street sleeper’ effect without a bonnet scoop or a snorkel in sight.

GARRY WEATHERSTONE
VT COMMODORE SS