DESOT THUNDER The Racing Begins When The Pavement Ends For These Tough Chevy Trucks
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Team MacPherson's 1000 off-road race.
ike Gila monsters, horned toads and scorpions, off-road racing is native to America's southwestern states. The terrain in the badlands can be as menacing as its wildlife, but that doesn't deter dedicated desert racers. They construct their specialized off-road racing machines to survive close encounters with boulders, gravel pits and oceans of silt. They train their bodies to withstand the punishment meted out by miles of non-existent roads and steel their nerves to drive flat-out into blinding clouds of dust. It takes tough men and even tougher machines to take on the desert. Three Chevrolet trucks are leading the charge in off-road racing. Team MacPherson fields a pair of off-road entries—the Goodwrench Performance Parts S-10, driven by Jerry McDonald in Class 7 4x4 and the Goodwrench Class 4 full-size pickup handled by Frank Arciero, Jr. Larry Ragland flies high in Class 7 with the Vector Promotions S-10. These rugged off-road racing machines are as technically advanced as any purebred competition car. Just as
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ft'rst fruck across the finish line at the legendar
Formula One road racers and NASCAR stock cars are built to meet the demands of their particular disciplines of racing, these trucks are constructed to cope with the harsh realities of racing without roads. Sophisticated suspensions, electronic fuel-injection and chrome-moly chassis are the new wave in off-road competition. Wheel travel is as important to an offroad truck as aerodynamics are to an IMSA GT prototype; transfer cases are as vital to off-road racers as turbochargers are to an Indy car team. Success in off-road competition requires more than a rock-solid truck and a rock-steady driver. It takes teamwork and organization to solve the logistical problems of pit stops on courses that can stretch across hundreds of miles of landscape that is as barren as the moon. The HDRA/ SCORE off-road racing circuit includes events from Baja California to Colorado—wherever the organizers can find terrain that would intimidate a rattlesnake. Just as North Carolina is the capital of stock car racing, Southern California has become headquarters for
many of America's top off-road teams. Chevy Thunder recently visited these dedicated drivers, designers and fabricators to discover the inner workings of off-road racing. What follows is an exclusive glimpse under the skins of their purposeful racing machines.
Team MacPherson S-1O Jerry McDonald and co-driver Joe MacPherson are stretching their advantage in Class 7 4x4 with their new long-wheelbase S-10 Maxi-Cab. The team won a championship in the four-wheel-drive mini-truck class in 1986 with a standard cab S-10. When McDonald began making plans for a new truck to defend his title in 1987, he decided that the Maxi-Cab was the way to go. "The Maxi-Cab S-10 offers the same advantages in off-road racing as it does on the street," McDonald explains. "I wanted more room inside
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r the driver's compartment to carry equipment. The extended wheelbase also helps the ride in rough terrain. "We've been pre-running off-road courses for the last four years with a Maxi-Cab S-10," he adds. "The long wheelbase chassis corners just as quickly as the short version and it definitely is more comfortable in the rough stuff." A rules revision at the start of the 1987 season required engine builder Ryan Falconer to destroke Team MacPherson's 2.8-liter 60-degree Chevy V6s to 2.5 liters. The rules on induction systems in Class 7 4x4 were liberalized at the same time, allowing one venturi for each cylinder. "Although our current V6s have less cubic inches than the engines that won the class championship, they actually put out a little more power," Jerry notes. "We're now using three twobarrel Weber carburetors, which allow the engines to run at higher rpm than the single two-barrel carburetor we ran in '86." Team MacPherson's S-10 relies heavily on production powertrain and uspension components. "We're using a Borg-Warner T5 five-speed manual transmission," McDonald reports. "It has the same gears and internal components as a production Camaro transmission, with a 2.95:1 first gear ratio. We've had exceptionally good results with this setup. "The rules require us to retain the production front differential. The combination of the Camaro gears and the stock S-10 differential actually gives our truck a unique advantage. I run the entire race with the transfer case in low range, which produces an overall final gear ratio of approximately 6:1 with the 3.07:1 axle ratio we've installed in the front and rear differentials. On high-speed sections, I can take advantage of the fivespeed's overdrive feature; even with the S-10's 32-inch tall tires, the engine will pull SOOOrpm in fourth and fifth gear. Top speed is HOmph." The Maxi-Cab's stock suspension components are subtly modified to increase wheel travel and to withstand the incessant pounding of potholes and rocks. "The rules for the stock mini-truck class require a stock-type suspension with stock mounts. We ;an beef up the pieces, but we aren't allowed to use exotic links. It's also illegal to change the location of the pivot points. We've been able to achieve 15 inches of rear wheel travel
Chevrolet 60degree V6 is fast and reliable in Jerry McDonald's Class 7 4x4.
Production four-wheel-drive S-10 front suspension is bolstered by triple shock absorbers.
by installing longer leaf springs and reworking the shackles. The Bilstein rear shocks are 'laid down' slightly to accommodate this wheel travel. "Our race truck's front suspension retains production S-10 control arms, spindles and short shafts. The ball joints and CV joints are modified to provide 11'/2 inches of wheel travel. We mount three shocks with external reservoirs on both sides of the front suspension. A single shock absorber would have to be huge to dissipate the heat generated in an off-road race; increasing the number of shocks reduces the load on each individual damper." Team MacPherson's Maxi-Cab is outfitted with innovative two-stage front torsion bars. These bars function much like progressive coil springs, increasing their resistance as the suspension compresses. "The twostage torsion bars really improve driver comfort and traction," McDonald
notes. "On smooth roads, the suspension is very nimble and 'loose', but when the truck hits a killer bump, the secondary portion of the bar provides the stiffness we need. The entire setup is adjustable so we can select the point at which the second stage becomes effective." Even hard-charging off-road racers use their brakes occasionally. Four Camaro discs haul the MacPherson S-10 down from speed. McDonald's evaluation is succinct: "They work real, real well," he says. McDonald and his Maxi-Cab closed the 1987 off-road racing season with a flourish, taking top honors in Class 7 4x4 in the legendary Baja 1000 off-road endurance race and finishing sixth in the overall standings. Team MacPherson's Goodwrench off-road racer was the first truck to cross the finish line—a full-size performance from a very special compact pickup.
as the Golden Gate bridge and its undercarriage seemingly has enough links, rockers and hardware to outfit a dozen Indy cars. Although the 1988 full-size Chevy pickup has a spacious passenger compartment, foot room is scarce in this particular example. After all, its all-aluminum, 600-horsepower small-block V8 is mounted directly below the windshield. "The engine is set back 16 inches from the stock location," McDonald reports. "Relocating the motor improved weight distribution and allowed us to center the front differential in the frame. This truck is one of very few vehicles that combines four-wheel drive with independent front suspension. It's introducing a new concept to off-road racing. "The front differential is from a 1988 full-size Chevy pickup," Jerry continues. "This differential gives our Class 4 race truck a unique advantage over its competition. The differential has a synchronizer similar to a manual transmission; when the transfer case is engaged, the driver can shift the front differential in and out at any speed. GM builds the only trucks that can do that. On winding roads and sandy surfaces, engaging the fourwheel drive makes an incredible difference." The steering knuckles, uprights and CV joints came directly from the Chevrolet parts bin labeled "One Ton Pickups." A Saginaw steering box controls a complex pendulum steering linkage that produces virtually zero bump steer as the front suspension cycles through its 20 inches of travel. This high-tech truck's Dana 60 rearend is located by four trailing links. Two additional links connect the rear axle to a pair of massive rocker arms. These rockers stroke eight shock absorbers and four coilover springs mounted above the rear axle. "The springs are two-stage," McDonald explains. "We can tailor the spring rates by changing the coils. We also control wheel travel with the shock absorbers. When the truck hits a big bump, the shocks slow down the suspension action." "The rear axle has 20 inches of travel," Jerry adds. "There's just no substitute for wheel travel." A Turbo 400 automatic transmission and a shortened Borg-Warner transfer case complete the drivetrain in this ultimate off-road truck. The sprint car specialists at Shaver Specialties Racing Engines assembled its 381-cubic-inch small-block with an
Is this the ultimate off-road truck? Frank Arciero, Jr., is aiming for an overall win in Team MacPherson's full-size four-wheel-drive Sportside.
assortment of Chevrolet heavy-duty components (see "Light Heavyweight," November 1987 Chevy Thunder). An aluminum Bow Tie engine block, Phase 5 cylinder heads and a forged steel crankshaft provide the irresistible force that propels this Class 4 contender. Even with its light alloy engine, Team MacPherson's Sportside tips the scales at 4500 pounds. "She's a heavyweight," McDonald admits, "but she's extremely strong. There's no doubt that this truck has raised the level of technology in off-road racing. And that's excactly what we set out to accomplish." Chevrolet's presence in off-road racing pays dividends in engineering labs and in dealer showrooms. Suspensions and drivetrains are tested at the limits of performance to improve their quality and reliability. Off-road racers like Jerry McDonald, Larry Ragland, Frank Arciero, Jr. and Danny Thompson are proving that nothing wins like a Chevy truck.
(Top) Rear suspension for the Class 4 pickup has no visible means of support—just a pair of massive rocker arms mounted behind the Dana 60 rear axle housing. (Above) Rocker arms operate a phalanx of springs and shock absorbers in the bed of Team MacPherson's Class 4 machine.
Replica Racer What does Chevy's new "Back Country" S-1Q have in common with Team MacPherson's championship-winning Class 7 4x4 pickup? Plenty! The "Back Country" package converts any four-wheel-drive S-10 into a replica of the 1986 HDRA/SCORE minitruck champion. The "Back Country" option includes a distinctive light bridge behind the cab with powerful off-road lamps. A brushguard with halogen fog and driving lamps leads the way for wilderness treks. A tubular rear bumper and front grill guard give this four-wheeler a rugged appearance. Black wheels with chrome accents, black bezels and grille, and a stripe package around the wheel arches enhance this pickup's muscular look. The "Back Country" S-10 is an example of Chevrolet's commitment to building specialty trucks. "These are limited production models that appeal to special segments of the market—people who want something just a bit different than the mass-market truck," says Chevrolet Truck
Marketing Manager John M. Kelley. Other "specialty trucks" to be offered in 1988 include the Suburban Outdoorsman, a four-wheel-drive version of Chevrolet's superwagon that is designed to meet the needs of hunters, fishermen and outdoor enthusiasts. The Serengeti S-10 Blazer caters to a different audience—city dwellers who appreciate the style of Chevy's sports/utility truck. The Serengeti features a full leather interior, a black paint scheme and gold "High Country" wheels. Serengeti S-lOs will be available in limited numbers in California, where they will surely gather around well-known watering holes from Beverly Hills to Malibu.