1952 GMC 450-D

Everything about it is justly famous, from the streamlined cab and fenders that trademark the great post-war restyling of trucks from General Motors, to a seemingly mandatory Detroit Diesel engine beneath its elongated, elegant hood. This middleweight 1952 GMC 450-D, however, isn't everything it seems to be, either in terms of history or the technology of its powertrain.

In 1952, GMC was in the process of expanding the availability of Detroit Diesels, likewise a General Motors product, across a broader swath of the commercial-truck lineup. At least partly, GM figured to make diesels more common once the Korean War escalated, with the fuel rationing of World War II still fresh in everyone's consciousness. The 71-series Detroit Diesel, so named for the displacement of each cylinder in cubic inches, was available in both four- and six-cylinder versions, along with a six-cylinder Detroit Diesel with 110 inches per cylinder. By 1952, GMC introduced the 450-D, with 2.5 tons of hauling capacity, a medium-duty truck, and diesel power--with a difference. Its engine was the Detroit Diesel 3-71, with just three inline cylinders.

The owner of this handsomely restored 450-D, Allen A. Koberlein of Honesdale, Pennsylvania, told us that this Detroit Diesel is essentially based on half of a more conventional, six-cylinder 6-71's block casting. The reason was that none of the larger 71-series diesels would fit inside the midsized GMC's engine bay, which was first laid out to accommodate the 270-cu.in. GMC straight-six. The 71's historic market longevity was due greatly to its adaptability, with its variations sharing key common pieces including connecting rods, pistons, main bearings and cylinder liners, in addition to its proprietary diesel-injection fuel system. The 3-71, fitted with a Roots-type blower for enhanced induction, produced 105hp from 213 cubic inches at 2,100 rpm.

Allen's truck was originally part of a large order placed by the U.S. Navy, which intended to use the trucks at its ordnance depots--good thinking; no spark ignition or flammable gasoline to worry about with high explosives everywhere you look. His was assembled at the GM Truck & Coach Division plant in Pontiac, Michigan, and assigned to naval weapons stations in South Carolina and Virginia. Through his research, Allen determined that a similar surviving 450-D, like his built with a van body, and with a serial number only 23 digits different, was assigned to the Navy at Norfolk, Virginia. His GMC eventually passed into the hands of the late Keith Herring of Goldsboro, North Carolina, itself a military town. Herring used the veteran Jimmy regularly, hauling antiques all the way down the East Coast between Cape Cod and Sarasota, Florida. In doing so, he noted that the truck's overall fuel economy commonly averaged 10 mpg, pretty decent for something with its lofty gross vehicle weight.

Equipped with the 3-71, the 450-D has a capability of 10 forward speeds, unusual for a truck of this size but necessary to optimize the diesel's power curve. The transmission is a five-speed manual Clark 204BO, and the rear axle is a two-speed Eaton, its ranges controlled through a T-handle on the shift lever, with 16,600-pound rear axles. Now bearing stake-flatbed bodywork, Allen's restoration theme has it nudging full authenticity, save mostly for the body-painted dashboard, some auxiliary gauges and cloth high-back seats boneyard-sourced from either a Nissan or a Toyota, he can't remember which.

No conversation about any vehicle powered by Series 71 is fully vocalized, shall we say, without discussing its sound. A signature element of the Series 71's design, and its auditory concerto, come from Detroit Diesel's use of the Roots blower, which is not the same thing as a supercharger. Not that anyone would notice the difference. It gives the two-stroke beat a unique altissimo voice.

"It definitely has a sound all its own, due mainly, I'd guess, to the blower," Allen said. "It's sort of like a whine, only not exactly."