Minnie Mo’s Muscle Machines

The demand for more powerful tractors has been a constant since the first such machine hit the field in the late 1800s. In the mid-1960s, that demand became insatiable. Anticipating this need, Minneapolis-Moline (M-M) set out on a crash course to develop higher-horsepower machines. Backed by the emerging long-stroke, big-bore, and highly durable engine platforms, in 1955, M-M tractors first matched the competition in power and then led the industry in building beefy tractors for the next 18 years. 

First Four-Cylinder Diesels

M-M first ventured into diesel power plants in the early 1950s with the model UDU. The diesel powering the UDU, the model D283-4, as the name implies, had 283 cubic inches of cylinder displacement (CID). From the beginning of diesel development, engineers stuck to one platform to burn a multitude of fuels. The 283-4 was turned out in gas, LP gas, and diesel versions so designated by a G (gas), LP (LP gas), and D (diesel) in the numbering prefixes. 

These early Minnie diesels were powerful enough, churning out 42 to 46 belt horsepower. Their rated engine speeds stayed constant at 1,300 rpm during the diesels’ years in production. The 283-4 had a phenomenal design, as witnessed by the fact that some of these engines are still in use powering pumping plants in irrigated fields across the West today.

Farmers yearned for even more power. Minneapolis-Moline management realized they had to quickly carve out a spot as a horsepower leader in the Midwest market or lose out to tractor giants like IHC, Deere, and Allis-Chalmers. 

With a sense of urgency that would mark Minneapolis-Moline for the next two decades came the glory years of Minnie-Mo muscle tractors. In 1955, the company unveiled its vaunted model D425A-6 diesel, which was first nestled inside the model GB-D tractor. This six-cylinder engine had 425.5 CID and was rated at 1,300 rpm, turning out nearly 44 hp. 

Minnie-Mo would stay with the D425A-6, using it in the models GVI (introduced in 1961) and G704 (1962). In both cases, the engine was cranked up to a rated 1,500 rpm. With that came a leap to 54 hp. Though never tested at Nebraska, the G704 was a history maker. It was the first production tractor to feature a factory-installed front-wheel-drive front axle. The effect of that advance (greater traction and, thus, more field horsepower) wouldn’t be tested until the G706.

The D509A-6 Engine Platform 

The G706, introduced in 1962, was the tractor in which the model D509A-6 diesel debuted. This engine had 509 CID and was originally rated at 1,600 rpm. When evaluated at Nebraska, the D509A-6 in the model G706 delivered nearly 102 hp. – a leap of more than 30 hp. in one engine advance.

The D509A-6 would serve some of the most popular Minnie-Mo muscle tractors of all time, including the G708 (1965), the G1000 (1966), the G900 (1968), the G1000 Vista (1968), and the A4T-1400 (M-M’s first four-wheel drive in 1964).

The D509A-6 began life operating at a rated speed of 1,600 rpm. That was jacked up to 1,800 in two years with the introduction of the G1000. Up to this point, M-M engineers had stuck with the Lanova combustion chamber design. This approach used an energy cell positioned opposite the fuel nozzle that injected diesel at almost a 90° angle to the top of the piston. Fuel was injected into a small combustion chamber indentation above the piston.

100-hp. Platform

That approach was scrubbed with the D585-6 diesel, which was unveiled in the model G-1350 in 1969. This diesel represented the first – and last – use of direct fuel injection by M-M. The D585-6 was a beast with 585 CID and a 2,200-rpm speed rating. It leaped to work, churning out nearly 95 hp. in the G1350, 100 hp. in the A4T-1600 (1970), and then 102 hp. in the G-1355 (1973).

The G-1355 and its diesel were the last products to bear the M-M logo. White Motor Corporation purchased Minneapolis-Moline in 1963. In 1973, White amalgamated M-M in its line, having previously absorbed Cockshutt and Oliver.

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