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Catapulting Camaro

When you have no less than 420hp available at the rear wheels you've got one damn' serious street car....

By Greg Brindley

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Crammed into the confines of the back seat, huddled up behind the passenger seat with the stereo pumping hard, I tried keeping my composure as the sleek coupe accelerated. One thing that went a long way in exacerbating my feelings was how it wasn't the in-dash stereo I had been listening to. Rather, it was the raucous exhaust that permeated through every centimetre of the body, every gram of body deadener and paint, into the cabin and into my head. There was no getting away from the howl of that screaming stroked small block Chevy.

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As the noise increased, so too did the height of the hairs on the back of my neck - the dark green Camaro catapulting itself forward at a rate of knots not normally expected of anything less than a twin turbocharged 550 horsepower Ferrari F50! It was loud all right, however not loud enough to confuse the senses. No siree. In my 'watching' brief I was able to view and feel perhaps a little more than would normally be expected as a front seat passenger. Highly obvious was how the owner of this mean beast, John Rumler, eased his right foot ever so slowly towards the floor, which I guess is why in fourth gear with the pedal finally mashed as far as it would go, the monstrous 315mm wide tyres started to let go - at 180 km/h!

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To be honest, I couldn't hear the tyres squeal, rather the realisation came with an increase in revs coinciding with some rear end movement, followed by John backing off ever so slightly to allow the tyres to scramble for traction. My emotions came as a result of my asking this self-confessed speed freak for a demo, to which he gladly obliged while adding "I'm no race car driver so I'll take it easy around the corners and only give it plenty in a straight line." Well, with three-up and a full tank of fuel, I have to tell you it was a ride well worth a significant place in the memory bank.

What makes John's 1995 Z28 Camaro so quick is a radical combination of forced induction, trick engine management and tough stroked internals. Strangely, this far from disqualifies it as a capable cruiser. Indeed, by equipping the engine with a relatively high (9.0:1) compression ratio, monster intercooler and MoTeC engine management, the Camaro can be driven around town like a pussycat. It cruises along effortlessly at 200 km/h and 3200 rpm, while planting the foot immediately transforms it into the king of the jungle.

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The story behind John's foray into the world of super high performance starts about 10 years back. See, up until then he simply couldn't afford something fast, let alone a triple outboard powered sea race boat! Ultimately, it was John's fetish for getting wet in race boats that steered him towards vehicles offering a similar feeling of speed on terra firma. American iron was and it seems always will be the slant, with a few 80s model cars coming and going before a 1987 GTA Trans Am took his fancy. "I intended playing around with it, perhaps fitting a supercharger, before I came to realise it was a little old and too heavy. So I looked at what else was on offer and concluded the Camaro was the way to go," John enthused.

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The decision made, John had David Pruit of Emco order a Canadian spec 'continental kitted' Z28 which, once landed, was converted to right hand drive by Powell Reaper of Buick Conversions. "Before ordering the car I planned on equipping it with a supercharger, and with the kits available in package form from the US, I had Powell perform the necessary surgery which would allow the supercharger and accessories to be fitted here without requiring modification." The package consisted of an 'S' trim Vortech supercharger, chip, Jet Hot coated 1¾-inch headers and complete three-inch Borla exhaust, which added up to around 400 horsepower. "I was happy enough with it for probably a couple of years, however once I started toying further, I ran into problems."

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Yep, when handed to Ian Weightman of Amberley Autos in Dandenong for a 'tune', a number of deficiencies were revealed. "The fuel pressure reg wasn't working too well and it was pinging badly, so much so that the only way I could see of solving the problem was to fit an aftermarket engine management system," said Ian. Knowing the engine was compromised, John gave Ian the go ahead. "Basically it went like this; only hours after giving the nod to a MoTeC computer, John phoned and asked me to fit a bigger cam. The next day he asked that whilst they were off, that the heads be tweaked, then he wanted a stroker crank. Ultimately he said to do whatever was needed for the engine to make good grunt!"

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Intent on building an engine capable of delivering monster grunt without going completely over the top, Ian designed a configuration that with the aid of the MoTeC would serve John's 'hoon' requirements without transforming the car into a pig. Strength was of course a priority and that meant a bottom end designed to cope with around 600 horsepower. Ian had the LT1 block tunnel-bored, deburred, bored 0.030 inches and decked prior to bolting in a new factory hi-volume oil pump and Russell Pans enlarged sump. After lots of searching, a suitable forged steel 383 stroker crank came up - turns out that due to the unusual 'push' clutch arrangement, a specific crank was needed. Ian surrounded the import item with Clevite bearings while topping it with factory rods and ARP bolts. Pistons are KB hypereutectic numbers with moly rings.

Larger 1.65 inch exhaust valves, Isky retainers, collets and springs, and Yella Terra roller rockers compliment minor porting and chamber modification of the factory alloy heads. The latter are pumped with confidence by a Chet Herbert hydraulic roller camshaft offering 510 thou lift and an advertised duration of 220 and 230 degrees, factory roller followers and hardened push rods.

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The combination's main protagonist is of course the Vortech supercharger, which Ian has complimented with a 10mm undersized pulley (increasing maximum boost from seven pounds to 9.5 psi), plus an intercooler - in itself a huge task. Fabricated to Ian's specs by K&J Radiators in Queensland, the 915mm wide by 630mm high by 90mm deep core sits where much of the front bumper honeycomb once was, and is connected to the supercharger with three inch piping.

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Rounding out the package is an M48 Pro MoTeC engine management computer, the afore-mentioned headers and a custom-made BGT clutch assembly. Otherwise, the six speed trans, tailshaft and differential remain at factory specification. Mind you, John hasn't sat back. As a matter of fact, there's been a host of other changes including a Ground Effects body kit and silver bonnet highlights, the work of Trevor Davis. Furthering the appeal are 17 x 11 and nine-inch wide ZR1 replica rims wrapped in 285/45 and 315/35 Dunlop P8000 tyres.

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Anticipating the possibility of popping the odd Targa roof (through monstrous torque and chassis bending), John imported a complete subframe connector kit, adjustable Edelbrock rear struts and an engine bay strut brace. Funny thing is, these inclusions have done little to enhance the car's handling ability. Then again, it could be that the radical torque plays havoc with the chassis.... You see, even with the car heavily tied down on Amberley Auto's dyno, the back wheels cut loose at 5000 rpm at an indicated 315kW! It was all over way before the fat woman had a chance to sing. Indeed, the camshaft is designed to make maximum power at around 6000 rpm with a maximum useable range of up to 6600. Of course we can argue till the sun goes down, however I reckon it'd be fair to suggest that maybe another 15 rear wheel kilowatts may have been achieved if the tyres hadn't gone up in smoke!

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It's all academic really, cos this is one bitchin mumma. I have to tell you, the speed increases so quickly and the scenery passes by in such a flash, that arguing about whether the engine produces 550 or 650 flywheel horsepower becomes something irrelevant. Bottom line is that my butt has sat in many a fast car, and John's Camaro qualifies as one of the quickest ever!

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