SMOKE RINGS
shrouding. It had a lower power rating than the aircraft version due to less available cooling airflow.
The primary and most widely built application for the T-1020 was an export version of the World War II 1941-42 M-3 light tank. The 1940-41 M-2 combat car and light tank, predecessors to the M-3, had been tested with Guiberson’s, some 41 of them, and one was also fitted to an experimental armored car from the Trackless Tank Corporation in 1940. The diesel version of the M-3 began service in 1941 and 1,285 were ordered. When the revised 1942 M-3A1 series debuted in 1942, 211 diesel powered versions were built.
Both the M-3 and M-3A1 were normally powered by a nine-cylinder, 262 hp at 2400 rpm, W670 (670ci) Continental radial that made 590 lbs-ft at 1700 rpm. The T-1020 delivered 245 hp at a lower 2250 rpm but a more potent 645 lbs-ft at 1300 rpm. If you go by anecdotal reports, the gas version was considerably peppier, but also thirstier. The gas M3 was rated at 2 mpg while the diesel delivered 3.5 mpg and had an increase in operational range from 70 to 90 miles on 54 gallons of fuel, a 30 percent increase.
The M-3 diesel’s fuel economy was welcome to the Brits, who used the M-3s in the vast North African desert against the German and Italians. American fuel standardization to gasoline worked against the widespread use of any frontline diesel vehicles, but the USMC used some Guiberson-powered M-3s in combat prior to 1944. Because the Navy always had diesel fuel available, it simplified the supply situation in smaller island-hopping operations in the Pacific Theater.
Once the T-1020 was in production, the engineering team at Guiberson began work on a larger radial diesel. This would become the T-1400. The T-1400 displaced 1402 ci from nine 5.75 x 6-inch cylinders and had a 14:1 compression ratio. It was rated for 350 to 375 hp at 2325 rpm and used 20.2 gallons per hour at full load, full power. It was designed to be used in medium tanks but research shows only 28 of the 300 M-3A1 medium tanks built in 1941 (the second generation of the M-3 medium) had T-1400s and they didn’t see service beyond tests. The stopgap M-3 medium “General Grant” line was already on the way to being replaced by the better M-4 “General Sherman” medium at that time and the diesel version of both tanks used the GM 6046 twin 6-71 setup. Oddly, another radial diesel was offered in the M4 late in the war in, a big Continental gasoline radial dieselized by Caterpillar and called the RD-1820. More on that in a later Vintage Smoke.
In digging through the history books, we found radial diesels fairly common around the world prior to WWII and we will bring you more of them as Vintage Smoke rolls along. There are a surprising number of Guiberson radials around, most of them NOS crate engines left over from WWII. A large number were sold surplus after the war to power orchard heating fans or pumps. Very few of the diesel M-3 tanks have survived and we could verify only five. The restored engine shown here belongs to Mike Moffitt, a diesel tech and engine restorer in the Pacific Northwest with a taste for the odd and obscure. Only recently finished, Mike’s T-1020 has begun making smoke at engine shows around the Pacific Northwest. Special thanks to Jim Gilmore and Mike Moffitt.