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Vortech V-1 S-Trim Supercharger - Bright Here, Bright Now

A Corvette Cognoscente Crafts A Retina-Roasting Rocket

Christopher R. Phillip Jun 1, 2008
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Arousing car enthusiasts' interest with a C4 can be a real challenge. Positioned in the nether region between vintage and late-model, even the nicest fourth-gens have a tough time generating the oohs and aahs of a C1 Vette, or eliciting the awe and respect the newer LS-powered models command.

So how do you make your C4 stand out among the 358,000-plus other Corvettes that were produced between 1984 and 1996? For Bob Lynn, vice president of the New South Wales Corvette Car Club in Sydney, Australia, ample horsepower and a super-rare paint color were the answers.

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"My Corvette obsession began 17 years ago," Lynn says. "I found a '72 454 coupe in Sunflower Yellow advertised in the local paper. After several inspections and a long testdrive, three weeks later it was mine." Soon, it was time for a second Corvette. Lynn got a deal on an '87 coupe, and it was that car that made him fall in love with the C4 architecture. Eventually, he found a '92 coupe advertised in Australia's Unique Cars magazine, and, in 1998, he added it to his collection.

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His Corvette was one of 678 painted in Yellow, the rarest color choice for a model year that produced 20,479 vehicles. "My Corvette was built in November 1991," he says. "It's the only one of its kind in Australia. It was halfway through being converted to right-hand drive when I first looked at it. Corvette Queensland, now known as Performax International, completed the conversion before I took ownership of it.

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The '92 model year was a watershed sea-son in the history of the C4. Whereas all '85-'91 base Corvettes were factory-equipped with the "Gen I" L98 small-block, '92 was the first model year in which the "Gen II" LT1 engine was offered as standard fare. Although it featured a familiar 4.00 x 3.48 bore/stroke configuration and displaced the same 350 ci, its reverse-flow cooling layout-in which the heads were cooled before the block-was the first-ever such application on a production Chevrolet V-8. Other significant upgrades included a short-runner intake manifold, higher-flowing heads, and a front-mounted OptiSpark ignition system.

Factory literature states that the LT1 was good for 300 hp at 5,000 rpm. That wasn't enough power for Lynn, who sent his car to Pro-Flo Performance of Sydney for a boost in displacement and a Vortech V-1 S-Trim supercharger.

Utilizing an Eagle 3.75-inch 4340 steel crank, Eagle 6.00-inch H-beam connecting rods, and SRP forged-aluminum blower pistons, Pro-Flo stroked the LT1 to 383 ci and lowered its compression to 8.5:1. The heads were then ported and treated to Ferrea 2.02/1.60 stainless steel valves, Isky double valvesprings, and Yella Terra 1.6-ratio roller rockers. Likewise, Pro-Flo retired the factory stick in favor of a Camtech custom hydraulic roller cam.

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Then came the, "bright" idea to paint the cylinder block yellow to match the exterior's coruscating color. "It was the engine-builder's idea, as he said the engine bay was a black hole and needed something to brighten it up. After a little thought, I agreed," Lynn says. Meanwhile, Peter Snell Powdercoating of Sydney applied a metallic-silver coating to the front suspension, the radiator, and other select engine components to further spruce up the underhood presentation.

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The fuel, ignition, intake, and exhaust systems were next. Pro-Flo's techs added Bosch 42-lb/hr injectors, a BBK 58mm throttle body, and port-matched the factory intake to the cylinder heads. Custom, ceramic-coated long-tube headers were then matched to the exhaust ports and installed. Pro-Flo also upgraded the ignition with a Crane Fireball HI-6 CD amplifier, '96 LT4 plug wires, and NGK BCPR6ES plugs. Initial dyno testing performed at Just Engine Management (JEM) in Sydney was overwhelmingly positive. "Our testing on motor alone produced 295 rwhp," Lynn says.

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Before it was time for fun, though, it was time for more power. Lynn sourced a Vortech V-1 S-Trim supercharger, assuming it would drop easily into the Corvette's engine compartment. There was a problem, however. The blower was designed for left-hand-drive applications, so Lynn's RHD Corvette would require a few engineering modifications. "The whole supercharger had to be raised approximately 20 mm, and a new idler pulley was made. This-along with slight modification to the inside of the hood-provided enough clearance for the new setup," he says.

A powdercoated air-to-air-intercooler from Mick's Metalcraft in Sydney was then mounted in front of the radiator to cool the 6-8 psi of boost exiting the blower. Motec of Croydon South, Victoria, supplied one of its M-48 Engine Management computers to handle the Corvette's ignition timing, fueling, and other engine functions.

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Other drivetrain components were also upgraded to handle the increase in output. A heavy-duty 700-R4 trans with a 2,400-stall torque converter propel the horsepower rearward to a Dana 36 rearend housing upgraded 3.07 gears (2.75s were stock). As he did with the engine, the owner had the transmission, driveshaft, and differential painted yellow.

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Cabin accoutrements were next. Lynn felt that his Corvette's original Light Beige interior needed an update, so he contacted All Trim in Sydney, whose craftsmen reupholstered the seats in Taupe leather and provided color-matched door panels. Lynn and his partner, Jenny McMillan, reinstalled the items and painted the plastic trim to match the interior's new color.

To complete his C4 project, Lynn added '96 Grand Sport wheels wrapped in Sumitomo HTRZ II rubber. They're stopped by Alcon four-piston calipers clamping 13-inch rotors up front and stock Corvette brakes in the rear. He also installed Bilstein shocks and lowered the rear ride height with long spring-hanger bolts.

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Subsequent dyno testing at JEM provided the data Lynn was looking for. His blown engine combo produced 385 hp at the rear wheels, which, according to him, made all the difference in the world, especially at track events. "It was as different as chalk and cheese [an Australian analogy applied to two items that are similar in appearance but have entirely different qualities] in throttle response and acceleration out of corners. The only way I can explain it is, instead of driving it out of a corner, it launches out of the corners. It just keeps accelerating until I have to slow down for the next," he says.

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Shortly thereafter, in November 2006, Lynn had his brightly hued Corvette out for another track day. With only 1,800 miles on the rebuilt engine, the block starved of oil and seized, "bending the crank," he says. Although heartbroken, he pulled the engine and sent it back to Pro-Flo Performance for a second rebuild, this time upgrading it to a winged sump and adding extra baffles to prevent oil starvation under hard cornering.

So what was all that effort worth? This never-mellow yellow Vette blasts through the quarter-mile in 11.98 seconds at 121 mph-around two seconds and 20 mph faster than a stock '92. "My aim was to have a car that not only looks stock, but is a sleeper at the same time. So this Corvette is a surprise package," Lynn says.

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"Even with all its power, it's still driveable on the street and is a good cruiser," he contin-ues. "Over the years of owning it, I've driven it all over Australia, traveled to our national conventions, and used it on vacations. Along the way, I earned trophies for Best C4 and First Place in Modified '91-'96 at the National Corvette Convention 2006.

"My C4 gets a good response at car shows because its color attracts people's attention first, and after they come over to look at the car, they can hear how healthy it sounds. It's funny-a lot of people say they don't like yellow, but they like it on the Corvette. I intend to keep it as long as possible and enjoy it. It's a great car to drive-anywhere.




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