Did you know that GMC built a V-12 engine? They sure did, and despite the name “Twin Six” it was NOT two V-6’s bolted together. It was actually one long case, with FOUR V-6 heads mounted to it! Now why on God’s Green Earth would GMC build such a monstrous engine you ask? To mount in the tractor trucks used to haul Minuteman Intercontinental Ballistic Missiles. For real!!
In 1963 GMC designed special purpose tractors to haul the Boeing Transporter/Erector semitrailers used to haul the Minuteman I missiles. The trailers were 65 feet long, 10 feet wide, 13 feet high, had over 8,000 cubic feet of space, weighed almost 25,000 pounds when EMPTY, and they cost a whopping $700,000 1963 US Dollars each! The GMC tractor provided all the power to not only move this massive trailer, but also to run the climate control and air conditioning both during road journeys and while stored.
Of course those days of mutually assured destruction have faded somewhat, and the nuclear weapon proliferation hopefully has subsided…but those Twin Six V-12’s are popping up in rat rods and custom built speedsters the world over! An outfit in Australia for example has built a fiberglass Roadster with one of these humongous beasts up front. The engine is so long that the frame had to be cut and lengthened to be able to get the V-12 mounted. According to the hot rod shop, the Twin Six as mounted to their Roadster has an RPM redline of 2400 so the horsepower output is fairly anemic for the weight and only comes in at 275 hp. But, the that low RPM engine wasn’t made for whining screaming 14,000 RPMs like those Kawasakis and Hondas, no sir, this husky sucker was made to PULL. And brother, pull it does. Because at only 1600 RPM, this baby puts out over 630 ft/lbs of torque. So if you ever need a Roadster looking hot rod to pull your house over to the next block, well baby we have the engine for you!