"Tucked in among the 200 or so cars that make the pilgrimage to Mac's Ice Cream every Sunday night in Tewksbury Massachusetts, there's litte about Preston Smith's 1985 IROC to distinguish it in a sea of low-key cruisers. Sure, its wearing high-tech rims and skins, but for a generation of enthusiasts no longer able to save its nickels and dimes for 409's, replacing the forgettable factory wheels and tires is usually the first swap made in the pursuit of performance... even though most will never realize the potential of the speed-rated rubber. To Smith's credit, the Camaro's external alterations do extend beyond the rolling stock, but under the color-robbing glare of florescent street lights, the painstakingly applied Sikkens Brilliant Red Metallic is muted down to a dull burgandy not unlike a factory tone.

For all intents, the car assumes the identity of a well-maintained stocker. Even when Preston idles away, there's little to hint of more than emasculated factory power; in 1985, Detroit was on the cusp of a performance renaissance, but power was still all bells and whistles and mirrors, trick decals and hot exhaust notes. Its tought to sell a performance image when, as Smith's IROC illustrates, the top power source is an anemic 305cid small block.

Its tougher still to build a respectable street machine from such limited resources without abandoning the car's factory roots. As the crowd at Mac's intimates by its warm reception when the IROC eases onto the lot, though, Preston managed to do just that. In fact, during the past four years, he's pieced together and improved upon what may very well be the fastest 305-powered street IROC in the country, as evidenced by a growing number of 10-second time slips. On D.O.T. street tires. Through the mufflers.

As Preston pointed out, the IROC's displacement wasn't an issue, but like most horsepower-hungry consumers, he was stymied by Chevrolet's seeming inability to pull horsepower out of diminutive engine blocks. "My original intent was to build an American car with a small, limited-displacement block that could be the cornerstone to a real street driven performance car. You see imported exotics doing it all the time, it bothered me that we couldn't do the same thing here".

To see what the stocker was really capeable of, Smith first revamped the original suspension. The front underpinnings were adjusted for negative camber alignment with a 1/8-inch toe-in, then Preston started replacing parts out back. The stock torque arm was swapped for a fully boxed unit and lower rear links, along with a tubular panhard rod. and progressive-wound springs. All bushings front and back were replaced with polyurethane parts, and stock shocks were trashed in favor of adjustable Koni oscillators. Global West tubular subframe connectors tie the car together. The rear brakes were also swapped for 12-3/16-inch Wilwood discs.

Now that the car was capeable of pushing the envelope on its less-than-steller potential, Preston began to up the ante under the hood. Electing to stay with the high-tech electronic fuel injection, he weighed his options and decided that the best way to meet his goals without sacrificing the car's street-driven capability or gas mileage was with a supercharger. "That way, I wouldn't have to put in a large overlap cam or higher compression". Rather than bust down the original, Preston bolted together a 1990-vintage 305 with splayed four-bolt mains while he continued to drive the IROC. The improved block was fitted with a forged crank, J.E. .030-inch-over hypereutectic pistons (with the tops ceramic-coated by Swain). Mechart stainless steel boxed rods and a Lingenfelter 272 hydraulic roller cam.

Cognizant of the need for the 305 to breathe, Smith topped the block with Air Flow Research Stage One street aluminum heads equipped with stainless steel roller rocker arms and big ceramic-coated valves. They're tied together by Arizona Speed Marine oversize runners connected to an Extrude-honed manifold base; the upper plenum has been ported and matched to the runners. An ASM 52mm throttle body with airfoil (flowing 750 cfm) and Bosch injectors (30 lb/hr) round out the induction.

Oh, yes, there's the matter of that Vortech supercharger - and the 16 pounds of boost Preston has dialed into it. Recognizing the potential side effects of such a highly squeezed intake charge, Smith fabricated a custom air-to-liquid intercooler with its own pump and radiator system; subsequent track testing revealed the intercooler was good for about 35 horsepower. Preston reins in the supercharger with an MSD boost retard; an MSD 6AL two-step spark intensifier is also employed, along with the stock (albeit indexed) distributor and Moroso heli-wound plug wires. An ACCEL power processor helps out the on-board computer system. The estimated power is approximately 550 hp at the flywheel.

That kind of power will cripple a stock driveline in short order, so the stock automatic was replaced with a 700-R4 modified by CJM Racing Transmissions utilizing B&M internals and an Art Carr 10-inch, 2500rpm stall-speed non-lockup torque converter. It all ties into a 3.54:1-geared Dana 44 which, even equipped with Moser axles, became the car's Achille's heel.

"At New England Dragway last summer, I jumped down into the low-1.5 second 60-foot times", Preston recollected. "Normally, that isn't a problem, but with a 3500-pound car, it is. I popped the spider gears inside the housing because the axle tubes were flexing. We're in the process of fitting the car with a nine-inch differential with 3.70 gears and a Detroit Locker and 35-spline axles. I even had to brace the back of the housing!".

Smith also intends to send the entire intake system-air plenum, runners, lower intake manifold and cylinder heads - to Extrude-Hone, where the whole package will be port-matched. "It should be good for about 20 hp" Preston noted. "It doesn't sound like much, but on this kind of car you can't achieve big power gains in a single step. All the easy things have already been done". The extra ponies should be enough to drop the 3745-pound (with driver) machine well into the 10-second time zone. It's already turned in a best of 10.975 on D.O.T.-approved 275/60-15 M&H tires; changing to slicks has lowered the times to 10.86, although the speed drops off a bit (125.3 versus 126.7 mph) "because the D.O.T. tires are more flexible, and tend to 'grow' a bit more at the top end...."