Autocross and road course racing has been around for decades, dipping in and out of fashion in favor of drag or street racing. In the past couple of years, a resurgence has occurred growing from local backyard tracks and parking lots, to the Goodguys’ events and even on television. The addiction of putting your vehicle to the test and running it hard into the corners is only elevated by the science involved in planning course lines, logging and adjusting tires, camber and engines, all for fun and glory.
Normally the sea of autocross competitors is full of classic muscle cars with a few late models and super cars thrown into the mix. This was a time when trucks were used to tow the purpose-built cars to the track so they could have some fun competing before loading the cars back into the haulers and heading back home. One company began to change that a couple of years ago, No Limit Engineering out of San Berdoo, California. The suspension parts manufacturer and hot rod shop is no stranger to the classic truck market but after having some fun on the track, owner Rob MacGregor sought to build a truck of his own to compete, the Silver Bullet F100 featured a few years back in Street Trucks. The truck was based on his Big-10 production chassis and outfitted with a Ford Racing motor, coil-overs and race seats. Rob would drive hours to race the Silver Bullet in the autocross competitions, where he would flog the truck around the track and then drive it back home, unlike some competitors that babied and trailered their race cars.
The interior features both race necessities and comfort with a full roll cage, Sik Speed race seats with Crow racing harnesses along with AutoMeter gauges.[/caption]
The truck caught the eye of fans and competitors alike, especially when it started beating some of the cars out on the courses. It helped to grow the truck classes and show that trucks could be true competitors in autocrossing and even haul a show display home! As Rob toured the country, his lap times shrunk as the wins piled up. Some competitors began to complain that he had built a race truck and it was unfair for him to compete. But the truck was 100% street legal, hell it even had a horn! Maybe it was because it had a number on the side, or probably it was the fact that a truck was beating their high end muscle cars! When the season was over, the ideas to top Silver Bullet began spinning around the shop like a weather vane. The trick was, they only had 3 months to complete it in time to hit the autocross track at the spring Goodguys Del Mar.
Starting with the ever popular C-10 platform, Rob and the guys at No Limit Engineering looked to build a street legal pickup that would have the same wheelbase, track width and weight as the classic muscle cars at the top of the autocross competitions. If they complained about a race truck before, their heads were really going to spin now. But Rob kept in mind that he wanted to build one that he would have no problems driving to and from the course or around town. Sure the cops might pull him over to check out the truck but it would have all of the parts needed to make it street legal and a menace on the track.
The top has been chopped 2 inches, the bed has been molded to the cab and the doors roadstered. All in the name of aerodynamics for faster times.[/caption]
A full 1 3/4-inch tube chassis was built at No Limit Engineering and solid mounted to the cab for rigidity and the bed was welded into the cab after being shortened making the truck a true unibody. The chassis was built to accommodate a shortened 107-inch wheelbase and 335/30/18 BF Goodrich g-Force T/A KDW tires over custom made 18×12-inch Intro billet wheels on a square track width. The wide tires allow for better handling in tight corners. Taking care of the suspension travel is a custom set of control arms sandwiching a Speedway Motors spindle, and Wilwood Wide 5 hub and brake setup. The wide 5 setup was used for light weight. A set of Ridetech Triple Adjustable coil-overs handle the travel of the suspension. The rear suspension features a Speedway Engineering quick change rear end with 4.11 gears and Quartermaster drive plates. The rear end hubs were setup with 1/2 degree of negative camber to aid in handling as well as a Speedway Engineering. The handling is taken care of by a 2-link torque arm setup with Ridetech coil-overs.
The wide 5 Wilwood brakes and hub were used for lighter weight. Custom billet aluminum Intro wheels were made in 18×12-inch to fit the wide 335/30/18 BF Goodrich g-Force T/A KDW tires.[/caption]
For better weight balance, the Energy Suspension LS motor mounts were set back and the cooling system was relocated to the rear just behind the custom fuel cell that saddles the rear end with an Aeromotive pump. A Howe custom built radiator and 16-inch Maradyne electric fan is ran through a custom built pressurized cooling tower with a Meziere electric high flow water pump. The motor to be built would need the race inspired cooling system for the short and hard runs as well as the freeway cruising this truck would see. The base is a LS 6.0L engine that was first taken to Wayne’s Engine Rebuilders in Riverside to be bored over turning it into a 6.1L engine. A set of LS1 heads were set into a 5 axis to be machined, ported and polished over at West Coast Cylinder Heads before everything headed back to the shop so that Mike Sullivan could assemble the motor. It was outfitted with Scat rods and CP Bullet Pistons. Comp Cams supplied the camshaft as well as the assembly parts for the cylinder heads assembled using ARP hardware. Professional Products fuel rails top things off with Fel Pro gaskets. Royal Purple fluids are used for high performance lubrication.
For extra torque on the track, a 5.3L intake manifold was added with a custom Spectre Performance air intake bringing in the cold air through custom air inlets in the Mar-K grille that was blocked off for better aero dynamics. A custom set of Gibson headers were made and thermal coated at Jet Hot that flows the exhaust gases through a Black Widow muffler. MSD plug wires and a Painless Performance wiring harness takes care of the electrical side of the high performance motor. Transferring power to the rear end is aluminum Inland Drive Line driveshaft connected to a Tremec TKO manual transmission with a McLeod clutch and flywheel. A Hurst shifter controls the gears. Providing fine tuning on braking options while cornering, a Wilwood tandem master cylinder and proportioning valves were installed front and center for easy adjustments.
The inside of the cab contains all of amenities needed for checking a race truck as well as many of the luxuries needed in a street driven vehicle. Race seats from Sik Speed and Crow 5-point race harnesses compliment upholstery on the custom door panels from EJ. The full roll cage ties into the custom sheet metal dash that houses Auto Meter Phantom II gauges and digital shift controller. A Speedway detachable steering hub and wheel connect to a Flaming River power rack in order to handle the tight corners. An old school wink mirror was installed in place of side mirrors which aren’t very aerodynamic. It has the basic amenities including an iPod controlled speaker setup which is also used to timing and tracking laps but the only power features are that of horses.
The truck’s history is in the workforce, it is a 3/4 ton Longhorn edition, that means a 10 foot long bed. Which was chopped down greatly and molded to the cab once the chassis was completed and powdercoated. For a lower profile and aerodynamics, the C-10 cab was chopped 2 inches and the rockers were trimmed as well. The doors were capped and the metal on the cab was filled in to mimic a window frame. Custom front and rear fender flares were crafted to provide clearance for the wide tires after the wheel openings were raised as well. A 1968 hood and Mar K grille where installed. Out back, the front grill openings were mimicked and Street Scene mesh was added to provide air flow to the cooling system. Once all of the sheet metal work was done, Marcel Venable and Edwin spent hours blocking the truck body straight before Marcel laid down House of Kolor Blue Blood Red paint from Coast Airbrush. A few goodies from Classic Industries finished things off.
Once the truck was done, testing was done at Adams Motorsports Park in Riverside and it began its tour against muscle cars and trucks looking for some competitive fun on the autocross courses. But this high horsepower, uni-body, handling race truck is still fully street legal, gets 22 miles to the gallon and Rob MacGregor will easily drive it hundreds of miles to compete and cruise it back home.
For video action of this truck and behind the scenes footage, visit www.streettrucksmag.com.
Text and Photos by Jason Mulligan
1969 Chevrolet C-10
No Limit Engineering