Unsurprisingly, the Twin Six wasn't exactly "fuel efficient". The idea for a V12 truck engine came about in the late 1950s. General Motors was interested in an engine that could rival the ...

Then, in 1961, GM unveiled the mighty Twin Six V12 derived from two new V6 engines, a perfect addition to the automaker's lineup of new truck engines. The result is an 11.5-liter (702.4 cubic ...