THE SUPER BEAST LIVES

1978 ALLIS-CHALMERS 8550

- JIM ALLEN

In the early 1970s, Allis-Chalmers joined the ranks of the manufacturers offering articulated four-wheel-drive tractors. They started by rebadging the Bearcat from Stieger in 1972 and calling it the model 440. This 160 horse tractor got them on the field as they developed a new model in-house. The 440 carried them through 1975 until the 7580 emerged in 1976 as Allis-Chalmer’s (A-C) first in-house articulated 4x4. It was a good tractor but a bit underwhelming in light of the fierce competition in the super tractor horsepower wars that were beginning to flare up.

Late in 1977, the 8550 debuted as A-C’s biggest tractor. They rated it at 250 drawbar horsepower, though the Nebraska test would give it a few more. While it wasn’t the biggest or most powerful tractor on the market, it was in the top tier and gave A-C plenty to crow about. A-C knew in advance it would need to up the ante and had begun the development of a new six-cylinder engine that would become known as the 6120T. It displaced 731 cubic inches and cranked out 300 flywheel horsepower. It was a destroked (5.625 vs 6.50) derivative of a line of 844 ci, 21000 and 25000 series diesels that had been on the truck, heavy equipment, marine and industrial market since 1968. Yeah, Allis-Chalmers had it’s own engine division, formerly the Buda Engine Company, which it acquired in 1953.