Keeping your CCKW kosher

RANGER
1st Sergeant
1st Sergeant
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Joined: Sat Jul 01, 2006 8:29 pm
Location: Nearest Motor Pool

Keeping your CCKW kosher

Post by RANGER »

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.
Last edited by RANGER on Tue Jan 06, 2009 3:10 am, edited 1 time in total.
US ARMY HONOR GRADUATE MECHANIC, Restorer of fine Jeeps, MV's, MVPA 40+yrs, DAV, Army Aircrew member, Donor to Military Museums & CAF, MV Hobby since 1945
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Ken Blythen
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Post by Ken Blythen »

Do you have a photo or more detail of the modified crankcase ventilation set-up?
I've been thinking of fitting a PCV valve, or a breather tube back to the air cleaner just for function, but if there was a standard modification I'll try to follow that style.
Also (if you don't mind me picking your brain!) which air cleaner was later - the one with a gauze strip around the outside or the one with the all-steel body? Was either one superior ?

Thanks again.
Ken
RANGER
1st Sergeant
1st Sergeant
Posts: 6510
Joined: Sat Jul 01, 2006 8:29 pm
Location: Nearest Motor Pool

Post by RANGER »

I have no photos that will scan of the kit for the PCV Modification described. It was part of a kit that does not show up in the TM10 or SNL Parts books. I doubt if any exist or that there is a parts man that would have a clue as to this early modificatin. I have seen a few early CCKWs with this mod on surplus CCKWs and that was years ago. If your engine has the early system, it will operate fine if you drive your truck enough to completely warm it up. The Army had thousands of CCKWS, some were just being moved with out getting up to temp, or shuffled around the Motorpool and the Crankcases were forming sludge and acids. The later improved systems instaled at the factory were more efficient, but the trucks still had to be driven at operating temp, and just moving them a few feet here and there was still a problem. I do not remember which Air Cleaners were more efficient, it does seem that the ones with the mesh were earlier. Remember GMC had two basic Air Cleaner types for CCKW, the type that clamped to the Die Cast Carburetor, and the Late Type, held on by a wingnut, that went with the system used on the Cast Iron Carburetor. All CCKW Air Cleaners were manufactured by AC, there were variations of the same part numbers as they improved them. The CCKW Air Cleaners for the Cast Iron Carburetors interchanged with those on the Dodge 3/4 Ton 4X4 WC, the 1 1/2 Ton 6X6 WC, and the 4 Ton Diamond T 6X6.
US ARMY HONOR GRADUATE MECHANIC, Restorer of fine Jeeps, MV's, MVPA 40+yrs, DAV, Army Aircrew member, Donor to Military Museums & CAF, MV Hobby since 1945
Other Hobby- Army Air Force & Busting Big Ass Military Imposters-Good at it