Progress in July:
The team at Mil-Spec Vehicle Restoration has made significant progress on several fronts with our CCKW 353 Fuel Truck this past month. The once tired-looking frame now appears virtually brand new and is beginning to resemble a truck once again!
This month saw the team focus on installing the remaining differential unit and the pillow block before hooking up all of the drive shafts. They also fabricated and installed new brake lines, refurbished the carburetor, distributor, and steering box, while also cleaning and sealing the fuel tank.
Front Differential, Drive Shafts & Wheel Hubs:
The Mil-Spec team completed their overhaul of the final differential unit for the Fuel Truck, this being for the front axle. Its rebuild involved a similar level of effort to the differentials in the rear and intermediate axles covered in the previous restoration update. The newly-rebuilt front differential is now installed on the Fuel Truck, as are the fully-refurbished drive shafts (and their associated universal joints) linking each of the differentials to the vehicle's transfer case.
Mil-Spec continued to fabricate and install new stainless steel brake lines around the Fuel Truck's frame over the past month. As part of this process, they replaced the damaged tee-fitting which links the hydrovac unit to the brake master cylinder (which was itself also replaced). For those unfamiliar, the hydrovac magnifies a vehicle's braking power so that a driver need only exert a small amount of force on the brake pedal to effect significantly greater hydraulic pressure on the brake drums. Heavily-laden CCKW trucks, with gross operating weights up to and even exceeding 20,000lbs, needed this ingenious device (developed by Bendix during the 1930s) to enable their safe operation. Updated variants of this same hydrovac design are in widespread use even to this day. For those wishing to learn more, there is a marvelous WWII-vintage military training film explaining the system HERE.
The distributor is an essential element in an engine's ignition system. It 'distributes' a high-voltage electrical impulse to the spark plug in each engine cylinder, triggering a spark (and thus combustion) in a precisely timed sequence. For the Fuel Truck's GMC 270 straight-six, this sequence runs with the following cylinder order (1-5-3-6-2-4) to ensure both efficient combustion and a smooth-running engine.
The distributor which came with our Fuel Truck was in rough condition. After disassembling it, the Mil-Spec team found the inner workings to be worn beyond economical repair. As a result, they cannibalized a New Old Stock (NOS) example to find replacement parts for the points, condenser, breaker plate, shaft, advance weights and springs needed to rebuild the original unit. Media-blasting the distributor housing's exterior to remove old coatings and surface corrosion, they repainted it and added a new data plate, suitably stamped with the appropriate model and serial numbers used on the original. The now fully-restored distributor awaits installation on the Fuel Truck's engine, which is presently undergoing overhaul.
The carburetor is another key engine component. When tuned correctly, it ensures that a precise mixture of fuel and air arrives in each cylinder so proper combustion can occur. While rough-looking in appearance externally, the carburetor which came with our Fuel Truck project remained in restorable condition. The team disassembled the unit, cleaned and inspected its parts, while also media-blasting and repainting the housing. During reassembly, they also adjusted the carburetor's float to make sure it would allow the appropriate level of fuel through to the engine (similarly to the way a float in a toilet cistern governs the level of water per flush). The now fully-refurbished carburetor also features a brand new set of gaskets, custom-fabricated in Mil-Spec's workshop.
The steering box is a small device attached to the base of the steering column which translates the driver's rotational input to the steering wheel into the pivoting action which guides the direction of the vehicle's front wheels.
Mil-Spec's team disassembled the steering box, then cleaned and inspected the parts. They had to replace the worn-out upper and lower bearings, fabricate new gaskets for the seals, and adjust the lower bearing pre-load and sector shaft back lash (to minimize the slop in the steering action). They then reassembled the unit, making sure to safety-wire the side-cover retaining bolts (to prevent them working loose after longterm use).