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Ageless Iron: IHC’s 100-hp. Wonder

In the early 1960s, International Harvester was the king of the horsepower hill, which was the result of its highly successful Farmall line of tractors. But the competition was nipping right at IHC’s heels. More powerful tractors boasting better transmissions, hydraulics, and operator features were eroding the firm’s market share.

IHC had introduced its New World of Power models 460 and 560 that boasted a new look and new six-cylinder engines. However, IHC still lacked a high-horsepower line.

The word went out from the IHC board of directors to its engineers asking them to “build ’em bigger.”

IHC engineers had already been at work fashioning a larger engine platform based on the six-cylinder they’d built for the New World of Power. Designers took that concept and put it on steroids. Beefed up in every way, a new 361-cubic-inch six-cylinder was created and was first debuted in the 1963 introduction of the model 806. This direct-injected diesel turned out an impressive 94½ PTO horsepower. 

The 806 and series mate 706 revealed much about the future of IHC tractors. Significant advances were incorporated in all aspects of the tractors. For example, the tractors were equipped with a two-speed range transmission offering 16 forward and eight reverse speeds in tractors equipped with a torque amplifier (TA). That TA consisted of a direct-drive clutch and a list of other advances that made the design extremely reliable. 

Then, too, the bull gear final drives for these tractors were placed in axle carriers, which were, in turn, mounted to the outside of the rear frame. This resulted in a stronger rear frame while allowing the bull gears to be widened to accommodate future horsepower increases without changing the rear frame.

To top off all these modifications, the rear axle of the 706 and 806 was designed to readily accommodate dual tires without resorting to aftermarket modifications.

With all this solid groundwork completed, the introduction of a more powerful IHC in 1966 was almost seamless. Save for some driveline enhancements, the model 1206 was an extension of the 806 – with one exception. The 1206 was turbocharged. With that advance came a boost in power. The 1206 churned out 18 more horses than the 806, achieving a rated 112½ PTO horsepower.

powerhouse couldn’t keep tires on

The 1206 was certainly a powerful tractor. Almost too powerful, since it was wrecking its rubber during prototype testing prior to its 1966 introduction. So IHC went to Firestone and Goodyear to get them to design tires for the tractor. That collaboration resulted in the venerable 18.4×38 heavy-duty tire that proved to be a mainstay for tractors for years to come.

The 1206 was also festooned with an impressive list of features it inherited from the 806 including:

  • Hydraulic draft control 
  • A three-point hitch with torsion bar lower-link sensing
  • Hydrostatic steering
  • Hydraulically actuated, self-adjusting brakes
  • A cooler for transmission and hydraulic oils
  • Dual-speed (540 and 1,000 rpm) PTO

The feature-rich, brawny 1206 was an instant hit with farmers. It sold for only two years (before being replaced by the model 1256 in 1968), just short of 10,000 model 1206s being sold, making it an unqualified hit for IHC.

More importantly, the 1206 provided a solid foundation that IHC would utilize to create seven +100-hp. tractors that would be introduced on into the next decade.

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