This monster of a GM V12 engine actually weighs more than a Mini Cooper

Published on Dec 09, 2025 at 10:00 PM (UTC+4)
by Grace Donohoe

Last updated on Dec 09, 2025 at 3:13 PM (UTC+4)
Edited by Amelia Jean Hershman-Jones

GM Motors is one of the most well-known vehicle manufacturers across the whole of the US, but we bet you didn’t know about this monster GM V12 engine.

Forget just providing power for cars and small vans, GM needed a mighty engine to make sure that its trucks boasted sheer power.

The result? A huge engine with unrivalled power that paved the way for others.

It’s so heavy that it’s like having a Mini Cooper hidden under the hood.

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The GM V12: Here’s what you need to know

It’s no secret that GM has a huge umbrella of models and automotive brands on offer, but forget the likes of Chevrolet, one huge turning point for the company was the GM V12 engine.

The powerhouse reportedly weighed up to a mighty 1,5000lbs, which is reportedly more than a ’60s era Mini Cooper – oh yes, the engine meant business.

Released in the ’60s, the engine was used to power huge GMC trucks on the open road thanks to its mighty capacity – but more on that later.

The huge engine reportedly had a limited production run of five years, ending in 1965, but thanks to the capabilities of the engineering, six decades later, it is still a talking point amongst gearheads.

Plus, firefighters and farmers also loved its alleged ability to move gallons of water at a time.

The huge crank and oil sump, able to hold four gallons, as well as other parts, made it a very popular choice.

The GM V12 engine had a deceiving nickname

Thanks to the sheer size and power that it produced, the engine earned the moniker of the ‘Twin Six’, but don’t be fooled, as it was still a single engine, and a vast one at that.

Don’t fear, though, as the V12 did share some similarities with the V6, 54 to be exact, and even used 56 head bolts.

The engine was able to pump out a mighty 275hp at 2400rpm and 630lb-ft of torque, all within an 11.5-liter capacity.

Seriously, this thing was huge and could haul masses of weight at a time, making GMC trucks the ultimate end destination, with tractors getting a look in too.

It reportedly also made big promises too, with minimal maintenance needed only after 15,000 miles, and major after 200,000 – which, compared to engines today, is impressive, you have to admit.

GM even proudly displayed this fact in an advert.

The engines are a super rare find, with many car enthusiasts battling it out to call one their own.

After all, the huge ‘twin six’ is a marvel of mechanical engineering.

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Grace started her career writing about the weird and wonderful for the international press. She's covered everything from lifestyle to sports and hard news and now finds herself pursuing her main interest - cars. She's loved cars from a young age and has a keen interest in luxury travel too.