Keeping your CCKW kosher
Posted: Wed Aug 02, 2006 7:25 pm
The following are three early fixes developed by Army and GMC engineers.
Bear in mind that the CCKW was subject to constant upgrades as reports in the field brought attention to deficiencies arising through operational service. Many of these changes resulted in deletion of old part numbers, resulting in substitution of improved parts. A restorer with an early discontinued. Some early improvements were simple, for example,the improved Air Cleaner Clamp Modification that replaced the easily damaged original on the early Air Cleaners. What happened was that mechanics and drivers would be too agressive in removing the Air Cleaner,and the clamp would distort, resulting in an air leak which allowed dirt to directly enter the carburetor.
A Positive Crankcase Ventilator and was designed to give positive ventilation under all conditions. It was found that the CCKWX and early CCKW crankcase vent system was not sufficient for CCKWs that had limited use or were subject to short runs resulting in harmful condensation in the crankcase. The fix was to seal the two louvres in the early rocker arm cover, and install a vacuum device that replaced the spacer beneath the carburetor that connected thru tubing that was supplied with the kit to fittings installed on the intake manifold.A new Oil Fill Pipe with Breather was also supplied. This mod was early, and not used on production models, as it was a field fix. This provided forced crankcase ventilation under all conditions and speeds.. There was also a special paint provided to use on the inside of the rocker arm cover to treat those that may have rusted or corroded as a result of the early system.
The improved Water Bypass was developed to replace the original bypass tube from the cylinder head to the radiator, resulting in a more efficient warm up system by recirculating warmer cylinder head coolant directly back thru the engine block.It also relieved pressures that would build up in the rear of the cylinder head due to steep downhill grades. This involved replacing the early tube and plugging the radiator where it formerly attached, and installing the new style tube that traveled from the rear of the cylinder head to the thermostat housing.
It is no sin to leave these GMC improvements, as they resulted in iimproved operation and longevity. To return to factory stock may not be good for your CCKWs health.
Bear in mind that the CCKW was subject to constant upgrades as reports in the field brought attention to deficiencies arising through operational service. Many of these changes resulted in deletion of old part numbers, resulting in substitution of improved parts. A restorer with an early discontinued. Some early improvements were simple, for example,the improved Air Cleaner Clamp Modification that replaced the easily damaged original on the early Air Cleaners. What happened was that mechanics and drivers would be too agressive in removing the Air Cleaner,and the clamp would distort, resulting in an air leak which allowed dirt to directly enter the carburetor.
A Positive Crankcase Ventilator and was designed to give positive ventilation under all conditions. It was found that the CCKWX and early CCKW crankcase vent system was not sufficient for CCKWs that had limited use or were subject to short runs resulting in harmful condensation in the crankcase. The fix was to seal the two louvres in the early rocker arm cover, and install a vacuum device that replaced the spacer beneath the carburetor that connected thru tubing that was supplied with the kit to fittings installed on the intake manifold.A new Oil Fill Pipe with Breather was also supplied. This mod was early, and not used on production models, as it was a field fix. This provided forced crankcase ventilation under all conditions and speeds.. There was also a special paint provided to use on the inside of the rocker arm cover to treat those that may have rusted or corroded as a result of the early system.
The improved Water Bypass was developed to replace the original bypass tube from the cylinder head to the radiator, resulting in a more efficient warm up system by recirculating warmer cylinder head coolant directly back thru the engine block.It also relieved pressures that would build up in the rear of the cylinder head due to steep downhill grades. This involved replacing the early tube and plugging the radiator where it formerly attached, and installing the new style tube that traveled from the rear of the cylinder head to the thermostat housing.
It is no sin to leave these GMC improvements, as they resulted in iimproved operation and longevity. To return to factory stock may not be good for your CCKWs health.