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The engine on its assembly stand during its rebuild. Note the installation of the distributor (with ignition leads), crank case ventilator air cleaner and the engine oil filter (grey cylinder). The upper oil pan is also in place, with a new instruction decal on the side, and the engine oil dipstick assembly attached as well. (photo via Mil-Spec Restoration)

CCKW Fuel Truck Rebuild - January, 2024:

The team at MilSpec Vehicle Restoration in Belvidere, New Jersey focused most of their attention this month on completing the rebuild and repainting of the CCKW Fuel Truck’s 6-cylinder GMC 270 engine, whilst also diverting a little energy to smaller details on the vehicle’s chassis.


The team refurbished the steel structure which holds the vehicle’s battery in place. The rear plate on this component needed replacing due to significant corrosion issues. They cut away the damaged part, fabricated a replacement and then welded it in place. Next they trial-fitted the assembly onto the vehicle’s chassis to ensure proper alignment before welding on an appropriate length of retaining angle along its bottom edge. After repainting, the fully restored ‘battery box’ was remounted on the vehicle.

The restoration team also installed a set of new rubber bumper blocks (with freshly overhauled and repainted housings) onto each of the trucks three axles.

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Another view of the engine during its reassembly. The generator and fan have yet to be installed - along with their associated drive belts running from the crankshaft pulley. The carburetor is in place, connected to the air intake manifold (green-painted ductwork) and the exhaust manifold (black-painted piping). (photo via Mil-Spec Restoration)


Engine reassembly really picked up steam this month. This effort began with the cam shaft. With its timing gear pressed onto the front end, the cam shaft assembly slid into the engine block. Tappets were placed in the engine block openings above each of the cam shaft’s six cams. Next the team installed the push rods, sliding them vertically into position above each tappet, with  the rocker shaft mounted above. These components are essential elements of the mechanism which opens and closes the intake and exhaust valves with precise timing. 

Essentially, the cam shaft rotates in sync with the engine’s crank shaft. The six cams along its length each nudge a tappet at the lower end of each push rod, which then agitates the rocker shaft above to appropriately position the engine intake and exhaust valves in sequence with the combustion process. Each stage requires careful adjustment, of course, but when working properly, this whole cycle repeats continuously during engine operation. Images from the engine overhaul manual are reproduced again below to show some of these details.

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A maintenance decal in place on the upper oil pan assembly. Note that the lower oil pan assembly is also attached below, as is the dipstick mount - the base of which is seen at right. (photo via Mil-Spec Restoration)

Oil Pan Installation:

With the above key items installed, the rebuild team then installed the oil pump in the crank case and new seals for the front cover. The upper oil pan was then installed to the bottom face of the crank case, along with its internal oil pump supply tube.

A new gasket was then fabricated for the engine’s lower oil pan, which was then screwed to the engine, each steel fastener torqued down evenly against copper washers, which deform to both help lock the bolts in place and improve the seal.

The crankshaft pulley was then installed to the front of the engine. This component is connected to the crankshaft; it powers the flexible belts which drive the cooling fan and generator. Numerous additional components and ancillary systems were also installed on the engine, from the carburetor, oil filter, fuel and water pumps (with their associated piping), the distributor, spark plugs and ignition lines and intake/exhaust manifolds, etc. 

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A view of the engine during the process of adding on the various ancillary components. Note that the crankshaft pulley is installed, but the various drive belts for turning the generator and the cooling fan have yet to be installed - nor have those components themselves. (photo via Mil-Spec Restoration)

Engine Testing:

With the engine now fully assembled, it was time to verify its operability. To begin that process, the restoration team transferred the engine to a test stand and hooked up an extension to the exhaust manifold for channeling the combustion gases safely outdoors. While the initial attempt at an engine start revealed a problem, the restoration team resolved this quickly with the installation of a freshly-rebuilt distributor; a drive gear pin in the original unit had sheared. 

Once the engine was running properly, the restoration team ran it for the requisite five hour test period. With the engine successfully returned to operating condition, next month should see the powerplant reinstalled in the truck!

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Running-in the engine on a test stand at Mil Spec's facility. Note the exhaust manifold has been connected to an extension pipe to ensure that waste gases are pumped safely outside the building. (photo via Mil-Spec Restoration)