Last Call: Twin Six Edition

gmc v12
There’s no better way to cap off the week than with some engine pron, I always say. The GMC Twin Six wasn’t really two V6 engines welded together but one honkin’ big V12 displacing 702 cubic inches and a forged crankshaft that tipped the scales at a robust 180-pounds. Pop that into the engine and add all the rest of the accessories and you’re looking at 1500-pounds for this torque monster. GMC built about 5,000 of these monsters.
Last Call indicates the end of Hooniverse’s broadcast day.  It’s meant to be an open forum for anyone and anything. Thread jacking is not only accepted, it’s encouraged.
Image: Go Away Garage


  1. Which vehicles were produced with this engine? From the sign in the background they were clearly installed in trucks. Must have been big ones.

  2. While it may not have been two welded together V6s, it did use four cylinder heads, four exhaust manifolds, and two intakes from their V6 engine line.

    1. Yes not welded but definitely two V6s joined together (obviously without two timing chains etc), just like the Aston Martin V12 although that doesn’t share as many V6 parts as this! It is probably worth noting from a modern perspective that this was near the end of the era of semi trucks running gasoline engines.
      This is also pretty common in large industrial diesel engines that have individual cylinder heads, they are made from 3 cylinders up to 48 cylinders (in a very) depending on how much power is needed.

      1. Given that you’re doubling the weight of the vehicle adding a flying bridge wouldn’t really mess with the center of gravity too much. Then you’d probably have a mini version of another Grubb creation, the Decoliner.

  3. -So, it’s time to decide how we’re going to advertise our new lineup of vans. Any idea ?
    -A happy family ready for vacation?
    -Nah, boring.
    -A young, sporty couple loading some camping equipment ?
    -How about some creepy, straight-out-of-your-nightmares clowns ?
    -That’s exactly what i was looking for ! Give that guy a promotion !

    View post on

  4. Tom Jones’ cover of Gillian Welch’s Elvis Presley Blues is kind of psychedelic. It reminds me of Scott Walker’s turn to the avant garde in the ’80s. (This has nowt to do with cars.) (Let’s try a Vevo imbed…)

      1. That’s an extremely weird take on a song that I love.
        Sounds like he’s channeling Bowie at a couple of points.
        Edit: Beats the hell out of Jimmy Buffett’s version. I won’t link it here, because I think Buffett should be locked in a van with the rest of the clowns.

        1. I only found out there was a Jimmy Buffett version today, while trying to find the proper songwriter’s credit. I didn’t bother listening to it.
          But, Hey! Gillian Welch and David Rawlings are my age, and that’s a little too young to have really experienced the career of Elvis Presley first hand. Tom Jones is just 5 years younger than Elvis, and Jimmy Buffett, at 10 years younger, is about the perfect age to have been hit hard by the Elvis phenomenon. I find it easier to understand Jones and Buffett singing it than Rawlings and Welch writing it!
          Maybe someone born 30 years after Michael Jackson (that’d be the late ’80s) is about to write a song that Sting and John Mellencamp will cover.

    1. somewhere on the web I saw some in cab footage of the above truck being flung around a muddy horse racing track. It looked wicked fun.

      1. Maybe if he wasn’t wearing hiking boots for the demo he might have more feel for what he’s doing. Regardless, that’s mighty impressive, looks like a blast.

        1. Absolutely! I change shoes just for driving along ordinary traffic…nowhere nesr those skills anyway.
          But this was about WS’s Fiesta – looking forward to see some photos!

  5. I came across a Bugatti Royale replica/hot rod that used one of these – note this is 77 cu in smaller than the original Bugatti engine!

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