A Hill 4R commercial generator set from about 1941; you can see several differences between this and the later unit. The 4R generator unit was produced right to the end of Hill Diesel in 1952.


Most of you know the Oldmobile name. And since you are a diesel enthusiast reading the world’s premier diesel enthusiast magazine, you’ll naturally connect that brand name to the infamous 78 Olds 350 diesel (see Diesel World June 2018). You may even know the Oldsmobile car was named after a very talented gent named Ransom E. Olds (1864-1950). Odds are slimmer that you know Mr. Olds was an early pioneer in the manufacture of diesel engines. This is the story of how he went over the Hill. Hill Diesel, that is.

Found in Jerry Biro’s extensive vintage diesel collection at Hercano Propulsion in Southeast Ohio, this unknown-vintage Hill 4R 15kW generator set is identical to a World War II PE-207A. The generator produced a 15 kW continuous rated load at 120/208 volts from a General Electric Model AST AC generator. The short-term load was 18.75 kW. The engine has a 24-volt starting system but could also be hand-cranked. As shown, this unit weighs in at around 4,000 pounds.


In 1883 Olds began working for his father and older brother at P.F. Olds & Son, a company that dealt mainly with steam power equipment. In 1890 he bought his brother’s share of the company and, seeing external combustion (steam) was on the way out, began pushing his father into a new direction: internal combustion. P.F. Olds & Son soon became the Olds Gasoline Engine Works, producing a variety of innovative engines from 1 to 50 horsepower. Some of them used a hot tube ignition, an idea that translated into the development of the diesel engine, then commonly known as an “oil” engine.

The Model R uses four Bosch APF injection pumps driven off lobes on the camshaft. A separate rack controlled the fuel delivery, but the pumps each had to be adjusted for timing and stroke via shims between the block and pump.

Olds began experimenting with motor vehicles in the late 1880s. By 1896 he had some salable ideas for a gasoline-powered automobile. Concurrent with the engine plant, Olds began the Olds Motor Wehicle Company in 1897 but needed cash to bring cars to volume production. Investors came in and though it diluted Olds’ interests and focus somewhat, he was still VP and General Manager of what Became Olds Motor Works. The gas engine plant was folded into the business but Olds wasn’t hands-on there any more. By 1910 that part of the company had become the Seager Engine Works under new owners.

The power and torque graph for the 4R shows maximum, intermittent, and continuous ratings. With a full load at 1,200 rpm, the engine used 1.6 gallons per hour according to the Army.

After a very rocky road that included his main plant burning to the ground, Olds introduced what have become known as the “Curved Dash” Oldsmobile cars in 1901. These became America’s first high-volume, best-selling automobile and formed the roots of the Oldsmobile brand that was slurped up by the new General Motors in 1908. Olds had departed the company by then, having left in 1904 during an internal dispute over new models. Olds then started Reo Motors in 1905 (“REO” from his initials), which quickly began outselling Oldsmobile. Olds soon debuted a line of Reo trucks that ended up with more staying power than the cars, which faded in the early 1930s. The Reo truck line lasted into the late 1950s.

Ransom Eli Olds poring over blueprints in 1901. At only 37 years of age he was already several steps up the ladder of success, but was poised for an elevator ride to the top. A talented, self-taught engineer, he was a natural businessman and that’s the part of his skill set that carried him the farthest. Certainly at the time he owned Hill Diesel he was still contributing technical ideas and getting his name on patents.

Ransom Olds was always looking for new ventures and in 1924 bought J.P. Edmonds’ stock shares of the Bates and Edmonds Motor Company. Madison F. Bates and James P. Edmonds had left the Olds Gasoline Engine Company in 1899, still basically on good terms with Olds, to start their own engine manufacturing firm in Lansing. Olds renamed it the Hill Diesel Engine Company, reportedly after Harry Hill, whom Olds put in charge, while remaining chairman of the board.

A cutaway view shows what would now be seen as an old-school IDI diesel. In 1940 it was cutting-edge tech. It had five main bearings, 2.9375-inch rod and main journals, and used dry sleeves. Lotta beef for a four-cylinder, with the engine alone weighing 1,560 pounds. Using an access plate on the block sides you could overhaul the engine without dropping the pan.

Bates and Edmonds had been building a well-respected oil engine since at least 1919. The Bull Dog was of the Hvid type (pronounced “Veed”), which was compression ignition but with a low-pressure fuel system. Under the Hill name it evolved into the model V, built with one through four cylinders (4.75×8-inch bore and stroke). The new Model A engine (6×10-inch bore and stroke) and the model B (5×7-inch bore and stroke) came along some time after 1924 and were similar in design, still using a Hvid injection system in four- or six-cylinder configuration.

A Hill 4R commercial generator set from about 1941; you can see several differences between this and the later unit. The 4R generator unit was produced right to the end of Hill Diesel in 1952.

By 1928 the Hill Models A and B had evolved into a prechamber diesel with a high-pressure injection system. Soon after, the more compact Type C engine (3.5×6-inch bore and stroke) debuted as a four- or six-cylinder, and this is when Ransom Olds made an effort to promote diesels in trucks. He had a Reo Speed Wagon truck repowered with a four-cylinder Type C diesel and sent it from Lansing to New York to deliver a Hill generator unit. While the trip was successful, economical, and uneventful, it did not lead to widespread use of Hill diesels in motor vehicles. The Model C did lead to the Type R diesel, which debuted in 1940, and this engine would be the last type built by Hill.

The Type R was similar to the Type C but destroked to 5.5 inches, and featured individual camshaft-driven Bosch APF injection pumps for each cylinder rather than an inline Hill pump. It was offered in two- (Model 2R), four- (4R), and six-cylinder (6R) configurations. The older designs were gradually discontinued as Model R production was ramped up, and the 1942 Hill catalogs do not show the older engines at all.

The Model Rs were offered as power generators or marine propulsion units. The two-cylinder displaced 106 cubic inches and made a maximum of 23 horsepower at 1,800 rpm, with the continuous rating a more modest 17.5 hp at 1,600. The 4R displaced 212 cubes, made 51.5 hp at 1,800 max (34 @ 1,600 continuous). The 6R was 318 cubic inches and made 78 hp at 1,800 max (52 @ 1,600 continuous). The continuous torque output of all engines were virtual straight lines from 600 to 1,500 rpm, delivering 60, 108, and 175 lb-ft, respectively. All of them had a 15.5:1 compression ratio. Some were equipped with individual compression releases for each cylinder so they could be hand-started.

In April of 1942 Hill Diesel was purchased by the Edwards Company of New York, with 78-year-old Ransom Olds retained as the chairman of the board. In reality, Edwards, a builder of power railway motor cars with a plant in North Carolina, was owned and run by the Cummins Diesel Engine Corporation of New York. Confused? We were until we learned that this was a company begun in 1934 as a distributor for Cummins diesels and had acquired Edwards in 1940. In August of 1942 they changed their name to the Rogers Diesel and Aircraft Corporation, operating both companies under their own names. The Edwards Plant was converted for the manufacture of wartime aircraft parts.

To confuse things even more, Drake America Corporation acquired Hill Diesel in 1948 as one of its first corporate acquisitions, and Hill limped along in Lansing until October of 1952, when Drake shut it down. It isn’t clear why. Very soon after shutting down, Hill’s remaining assets were sold off and its extensive parts inventory changed hands many times over the years. Of the many thousands of Hill Diesels built over the years, the Model R is probably the easiest to get parts for. Hill remains one of the best, but least known, of the defunct diesel engine manufacturers.

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