GMC’s Remarkable Twin Six Engine: The Story Behind General Motor’s Monstrous V12 – SlashGear

With everything installed, General Motors’ Twin Six V12 engine tipped the scales at a portly 1,500 pounds, making it heavier than many entire compact or midsize cars. It has an oil sump holding four gallons of oil (15 liters) and a high-volume oil pump to circulate 17 gallons per minute. The water pump is equally massive and could push 118 gallons per minute to keep the leviathan cool.

The GM Twin Six V12 produces 275 horsepower (at 2,400 rpm). More importantly, it offers 630 lb-ft of torque at just above idling speed (or roughly 1,600 rpm), making it suitable for extreme duty applications in the commercial, agricultural, military, and defense sectors. But above all, GM claims the Twin Six V12 could last up to 200,000 miles before a complete overhaul. Oh, and its fuel economy is a mere 3 mpg.

The Twin Six V12 was in production from 1961 to 1965 only. Its predecessor, a 10.5 liter (637 cubic inch) 60-degree V8, has a similar 4.56-inch bore and 3.59-inch stroke as the Twin Six. More importantly, the V8 was more compact, weighed less, and was cheaper to manufacture.