An interesting truck

jdv · Aug 25, 2014

Went to a swop meet over the weekend, it was at a museum that had some old and cool stuff I thought I would share a couple of pics. The GMC has a V12 installed in it. 702cubes of Awesome! And a pic of a Rummly. Don't get to see tractors like that in our area.

ShadetreeRet · Aug 25, 2014

I would hate to buy the gas for that GMC! Thanks for sharing.

Dean · Aug 26, 2014

Now that is cool.

They made even bigger V12s for larger trucks back in the day.

Dean

Jeff NWOH · Aug 26, 2014

I've heard rumors of those V12s, but never seen one.

I used to have an old GMC 6000 that had the 432 ci version of that v6.

snoop · Aug 26, 2014

Question: Is that a 'single' engine or two V-6's married together under the hood? Regardless ... interesting to see and thanks for sharing!

MarkB_MI · Aug 26, 2014

Probably a V12. The V12 Jimmys had a single block and full-length heads, but shared many components with the V6s.

mkirsch · Aug 26, 2014

It's a single block.

Here it is running:

https://www.youtube.com/watch?v=3Cd0nIdD-8Q

Gambles · Aug 26, 2014

The local machine shop did some work on a GMC V12 about a year ago. They purposely had the block setting there for all the walk-ins to see it. They said it was going into a puller of some sort. For some reason the owner couldn't come up with the money for the machine shop bill and it sat there for months.

just another old geezer · Aug 26, 2014

I bet that truck would pass anything on the road but a gas station.

8v92guy · Aug 26, 2014

The gmc 702 does not have full length heads. it has 4 heads and 4 exhaust manifolds. the block is one piece. We have 4 of those engines.

jeffcat · Aug 26, 2014

Hey adjust your eye balls. They have a LP tank in the back. Those trucks have the gas tank under the seat and both on Utube have the filler hole blocked off. Eco friendly and PC correct! lol

Mike (WA) · Aug 26, 2014

I would hate to buy the propane for that GMC! Thanks for sharing.

ss55 · Aug 26, 2014

I would guess the truck is custom built.

There are two dipsticks on the passenger side of the engine. It looks like the rear one is for an automatic transmission. Did they use a Turbo-Hydramatic 400 automatic transmission, or did they use something bigger like an Allison transmission?

Steve@Advance · Aug 26, 2014

I've heard of the V12 GMC's, never seen a real live one.

That would be a torque monster!

Wonder if that's the truck it came in? If you could ever got a good bite, bet it would twist something in two!

OleDawg · Aug 26, 2014

He uses the same type of heater hose plug that I do!!

dr sportster · Aug 26, 2014

I think I read about this engine in a new Rat Rod book. Common crank and block yet everything else almost like two separtate engines. Not sure about ignition?

ShadetreeRet · Aug 26, 2014

jeffcat,Thanks for the clarification. I saw the tank on the back, but I didn't realize that the truck ran on propane. I still wouldn't want to pay for the propane. I think I saw something about those engines recently, weren't they built for a special purpose or project?

rusty6 · Aug 26, 2014

I bet that is what is known as the GMC "Twin six". A big truck engine that had 12 cylinders, one block and 4 heads. http://www.curbsideclassic.com/blog/the-gmc-twin-six-v12-702-cubes-275-hp-at-2400-rpm-630-ft-lbs-at-1600-rpm/
Twin Six

Gambles · Aug 26, 2014

Two separate distributors.

Anonymous-0 · Aug 26, 2014

very neat truck first one I ever saw!! Thanks for the pic's !!!!!!!!

MarkB_MI · Aug 26, 2014

92 Series, I stand corrected. It's been awhile since I saw one of those engines. I think now it was a 12v71 head I remember seeing.

MarkB_MI · Aug 26, 2014

Those V12 Jimmys were popular as natural gas irrigation engines when I was growing up. And our school had a big rear-engined GMC school bus with a 702.

We owned a couple of GMC trucks with the V6. One was a half ton pickup with a four-speed automatic trans. I've never seen another truck with that transmission. Acceleration was excruciatingly slow, but it didn't seem to matter what the load was. Loaded or empty the acceleration was pretty much the same.

An interesting truck

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