Homebuilt 1942 Ford GPW Flatfender - Science Project

    Homebuilt Flatfender

    Harry WagnerPhotographer, Writer

    When Brian Sumner first got involved in four-wheeling, he was driving a Ford Explorer. He lifted the Explorer and added some aftermarket accessories, but it soon became obvious that Sumner needed a more extreme vehicle if he wanted to explore the bevy of rocky canyons found around his home of Albuquerque, New Mexico. Sumner considered buying a built rig to save time and money, but instead he decided to build his own rig from the ground up. The rationale was that this would allow him intimate knowledge of all his Jeep's functions, and it was also a great way to put into practice the theories he was learning as a mechanical engineering student at the University of New Mexico.

    A '42 Ford GPW that was rotting in his grandfather's yard served as the foundation of his project. The flatty had acted has a hunting rig for Sumner's grandfather before becoming a yard ornament for the past 20 years. Sumner and his father performed all the work on this vehicle in their driveway and two-car garage, from the tube-bending to the gear setup. The build took nearly as long as our own All-American flatfender project, but the end result is something that makes no compromises and is exactly what Sumner dreamed of.

    To begin, the stock GPW frame was fully boxed and fitted with outboard spring hangers to accept full-width axles. Sumner built dropped spring hangers to provide lift and allow the use of relatively flat leaf springs front and rear. A traction bar was added in the rear to keep the springs alive, and Rancho RS9000 adjustable shocks smooth out the bumps at all four corners. The suspension, in conjunction with trimmed fenders, provides enough clearance for 38-inch Super Swamper TSL tires.

    Four-wheel disc brakes stop the GPW with the help of a trick Vanco Power Brake Supply Hydroboost System that fits nicely under the hood and can lock up all four 38s. The braking is needed to reign in the flatfender after bursts of speed from the built small-block. Sumner loaded the 350ci Chevy with 1.5:1 roller rockers, an Edelbrock cam and intake manifold, block hugger headers, HEI ignition, and a Quadrajet carb. From there the power is routed through an SM420 gearbox mated to a Dana 300 transfer case with a Novak adapter. This drivetrain is stout, yet it's short enough to fit in the flatfender and still allow enough room for a rear driveline.

    Square-tube driveshafts were built with yokes from an XJ Cherokee to transfer power from the transfer case to the axles. The driveshafts are durable, offer long travel, and are inexpensive; however, they are not suitable for high speeds due to their inherent inability to balance. The rear axle is a full-floating Corporate 14-bolt with 5.13 Yukon gears, a Detroit Locker, and disc brakes that use factory Chevy rotors and calipers on custom brackets. The front axle is an eight-lug Dana 44 with matching 5.13s, a Detroit Locker, Warn chrome-moly axles, Longfield U-joints, and flat-top knuckles. Atop the knuckles sit Rockstomper steering arms that connect the axle to the Saginaw steering box and Chief hydraulic ram with 1-ton Chevy tie-rod ends and 1.25-inch and 0.219-inch-wall DOM tubing.

    With the drivetrain complete, Sumner turned his attention to the GPW's sheetmetal. He knew the vehicle would be subject to hard trail use, so more effort was made to make the body safe rather than pretty. The entire floor was replaced with 14-gauge patch panels, and the rear fenders were cut all the way to the rear of the tub in order to allow the wheelbase to be stretched to 92 inches. Sumner built the 'cage from 1.75x0.120-inch and 1.25x0.120-inch HREW tube with a Pro Tools 105HD bender and a Millermatic 35 MIG welder. The 'cage is tied to the frame at six points and features a multitude of crossbars and braces. An aluminum roof was added to keep the sun and rain off of Sumner and keep rocks from entering the cab in the event of a rollover.

    The Summit Racing plastic bucket seats and G Force Racing Gear harnesses are also tied in to the 'cage for added safety. In order to allow more legroom, the rear fenders were tubbed and the seats were shoved rearward before Herculiner was applied to the interior and under the tub. The exterior of the flatfender was sprayed with Royal Blue paint and fitted with custom diamond-plate corners that Sumner built himself.

    The seat mounting required the stock gas tank to be scrapped, so Sumner mounted a 20-gallon aluminum fuel cell between the rear wheelwells along with an Optima RedTop battery. A rack was integrated into the 'cage above the fuel cell to both protect it and provide a place to store tools, spare parts, and lunch on the trail. Other interior features include the hanging pedals from a Wrangler, a custom aluminum dash with Auto Meter Phantom gauges, and an aluminum quick-release hub for the Grant steering wheel.

    The thing that we like most about this vehicle is the great attention to detail. From the properly placed bumpstops to the clean wiring, Sumner took no shortcuts. That said, he still plans to swap out the carburetor for a TBI setup and replace the current wheels with Hummer double beadlocks to alleviate concerns about losing a bead. But after building for five years on a college student's budget, those details can be sorted out later. For now, Sumner is just enjoying himself out on the trail.


    Year/Make/Model: '42 GPW flatfender
    Owner/Hometown: Brian SumnerAlbuquerque, NM
    Engine: Chevy 350 small-block V-8
    Transmission: Muncie SM420
    Transfer Case: Dana 300
    Frontend: Dana 44 w/Detroit Locker,
    Warn axles/hubs,
    Longfield U-joints
    Rearend: Corporate 14-bolt w/
    Detroit Locker, disc brakes
    Ring-and-pinion: 5.38
    Suspension: Spring-over w/shackle reversal, Rancho shocks
    Tires/Wheels: 38.5x14.5R16.5 Super Swamper TSL/SX/16.5x10 steel wheels