Is It a K6 or K7

[MikePhua]

The Mystery of Mid-War International Trucks
Identifying vintage trucks from the 1940s can be a challenge, especially when dealing with International Harvester’s K-series lineup. The K6 and K7 models, produced during the World War II era, share many visual and mechanical similarities. Distinguishing between them often requires close inspection of trim details, serial numbers, and historical context. These trucks were built during a time of material shortages and government contracts, which led to variations in paint, chrome, and configurations.
International Harvester, founded in 1902 through the merger of McCormick Harvesting Machine Company and Deering Harvester Company, became a major supplier of agricultural and military vehicles. By the 1940s, the company was producing thousands of trucks annually, many of which were absorbed into wartime service. The K-series was introduced in 1940 and ran until 1946, after which the KB-series took over with updated styling and features.
Chrome and Paint Clues
One of the most telling signs of a wartime truck is the absence of chrome. During World War II, chromium was considered a strategic material and was restricted for civilian use. Trucks built for government agencies or military use often featured painted grilles and trim instead of chrome. A K6 or K7 with gray paint and minimal chrome likely served in a government role, possibly under the Department of Defense or Department of Energy.
In some cases, trucks were painted gray to match the standard fleet colors used by federal agencies. Anecdotes from eastern Washington describe K-series trucks recovered from Hanford Works, a site known for its role in the Manhattan Project. These trucks, painted gray and devoid of chrome, were in remarkably good condition decades later, suggesting they were stored or maintained with care.
Serial Numbers and Historical Records
To definitively identify a K6 or K7, the serial number is key. These numbers can be cross-referenced with archives maintained by institutions like the Wisconsin Historical Society, which holds extensive records on International Harvester production. The K6 typically had a gross vehicle weight rating (GVWR) around 16,000 pounds, while the K7 was rated closer to 20,000 pounds. Differences in axle configuration, frame strength, and engine options also help distinguish the two.
The K6 often came with a Blue Diamond inline-six engine, producing around 90 horsepower. The K7, designed for heavier loads, sometimes featured larger displacement engines or dual rear wheels. However, wartime modifications and field repairs could blur these distinctions.
Family Stories and Forgotten Machines
One story from the Ozarks recounts a K-series truck used to develop property near Table Rock Lake during the damming project. The truck sat idle for years, becoming a fixture in the landscape. Eventually, neighbors complained, prompting the owner to install new tires, ignition wires, and a license plate. The truck was driven to a farm, where it became part of family lore. Children remember standing beside their father in the cab, watching rust flakes swirl in the sunlight.
Today, the truck sits with rotted tires and chewed wires, but the engine remains free. Plans to revive it include installing new ignition wires, strapping on a temporary fuel tank, and attempting a pull-start. Such efforts reflect the enduring appeal of vintage machinery and the emotional connections they carry.
Government Equipment and Hidden Histories
During the 1940s, several manufacturers supplied trucks to the U.S. government. International Harvester was joined by Corn Queen, Federal, and REO in producing vehicles for military and departmental use. These trucks were often modified for specific tasks, such as hauling equipment, transporting personnel, or supporting infrastructure projects.
One lesser-known story involves contaminated rail cars at Hanford, which were buried due to radioactive exposure. A switch locomotive and two boxcars were reportedly sealed in a massive pit after a leak in the early 1950s. The cars had been lettered with false logos and numbers to disguise their contents—an operation carried out by workers tasked with maintaining secrecy. These buried relics serve as a reminder of the hidden costs of technological advancement.
Radiation and Risk in the Field
Workers at Hanford in the 1970s recall burying low-level radioactive waste using bulldozers and scrapers. Daily scans and radiation badges were part of the routine. One machinist was limited to 15 minutes of work per day due to exposure levels, yet still received full pay. These conditions highlight the risks faced by those maintaining the infrastructure of nuclear development.
Despite the dangers, many workers look back on the experience with a mix of pride and unease. The equipment used—often modified K-series trucks and heavy machinery—played a crucial role in shaping the post-war landscape.
Recommendations for Restoration
For those restoring a K6 or K7, consider the following:

• Inspect the serial number and cross-reference with historical databases
  
• Examine paint layers for signs of government gray or military olive drab
  
• Check for dual rear wheels or reinforced frames indicating a K7
  
• Replace ignition components with period-correct parts when possible
  
• Use modern tires with vintage tread patterns for authenticity
  
• Preserve original trim, even if damaged, to maintain historical integrity
  

Conclusion
The K6 and K7 trucks from International Harvester represent more than mechanical utility—they are artifacts of a complex era. Whether serving on farms, construction sites, or government facilities, these machines carried the weight of progress and secrecy. Identifying and restoring them requires not just technical skill, but an appreciation for the stories embedded in their steel.