Yes, GMC made a V12 engine. And it was huge

When you think of a V12 engine, your mind runs immediately to the high-tech, rev-happy, screamers made by Ferrari and Lamborghini. But did you know that between 1960 and 1965 GMC made a V12 of their own? And it was the size of two Ferrari 599 V12s combined.

It’s outrageous now to think of a gasoline-powered semi-truck but, in the 1960s when fuel was cheaper, a sizeable percentage of operators preferred gasoline power. Chevrolet offered a heavy-duty version of its famous 427 V8 to truck operators, but GMC knew they could do one better. They needed an engine with cubic inches, and lots of them. So they took the basic design from their 5.7L V6 and made a monstrous 11.5L V12.

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This was not just two V6s bolted or welded together. The V12 had its own block, cam, a special oil pan that held 15L of oil, and a special crankshaft that weighed 82 kilograms. The engine was an absolute monolith. It was 1.3 metres long and weighed more than 680 kg fully assembled. Due to its inherent weight and girth, it wasn’t an engine you could simply bolt into a Chevy C10 pickup and drive around in. It was installed in full-on semi-trucks, and also as standalone power units for irrigation. It was never installed into a passenger car or truck by GMC, but many hot-rodders have shoved it into service for hot rods, and custom pickup-trucks.

For all its size and displacement, the V12 wasn’t a horsepower king, it was made for torque. It made just 275 hp at 2,400 rpm but produced a freight-train-like 625-lb.-ft. of torque at just 2,100 rpm. If those numbers aren’t enough for you, a Florida-based shop called Thunder V12 will happily sell you a rebuilt one in any specification from bone stock to tractor-pull stormer. Prices start at US$10,800 for a complete engine, so get your chequebook ready. Beat-up originals can be found on eBay for around $5,000, but buyer beware as no more spare parts are being made for these beasts.

The GMC V12 was made between 1960 and 1965 and, in that time, they made about 5,000 of them. Nobody’s sure quite how many are left but most guess that there can’t be any more than 1,500 in semi-serviceable condition. After the big V12 ran out of production the writing was on the wall for gasoline-powered trucks. At 11.5L it remains one of the largest gas engines that ever powered a road vehicle, and we’ll never see a dinosaur like it again.

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