Anyone ever heard of a GMC V12?

I occasionally troll C/L for Jag xjs's because I'm a masochistic fool, but I will save that story for a different thread. Tonight, while searching "V12" I stumbled upon this...

GMC 702 CI V12 rare

Seller said: Up for your consideration is a very rare early 60s vintage gmc v12 engine.Massive 702 cid,1495lbs monster.This months car craft did an article on this engine and says there are less than 200 known left in the world.Would make the ultimate street rod power plant.In as pulled condition,and as complete as it gets.Rare is the word here.There were 2 on ebay and they were long blocks and the price was 10k.I m not looking for anything near that,and mine is complete carbs to pan.Slim chance to ever own another one that is affordable.This thing is awesome. in every respect,,

I don't even want to know where you'd get electrical stuff for that pig.

Big slug of an engine built for OTR trucks before diesel was the only way to go.

I'd bet there's WAY more than 200 left.

No, it wouldn't make the ultimate street rod powerplant. No transmissions will fit that you would want to deal with in a light car, it's heavy, it doesn't rev and it sucks fuel like no tomorrow.

It's neat but I wouldn't want one for anything more than display purposes.

They had a couple sizes, IIRC the 720 was the biggest. It's basicly a V12 block with V6 parts added on from the big GMC truck sixes.

You get a single block with four heads, four valvecovers, four exhaust manifolds, two distributors, two intake manifolds and two carburetors.

Shawn

It's basically a pair of GMC V6's joined together. They were all about torque and disregard the rest. From back when GMC actually had their own engineers and wasn't Chevrolet + badges.

Someone has one of those in a handbuilt bugatti replica street rod, I don't think it runs yet though. Btw the v6 ones in the pickups sometimes have plaid valve covers, kinda cool lol.

mndsm wrote: I don't even want to know where you'd get electrical stuff for that pig.

Some googling shows it to be two GMC 351 V6s(1960-1965) sharing a common block and crank. Heads, intakes, carbs, pistons, rods, dizzy innards etc are all the standard 351 fare. Looks like plug wires would need to be one-off, however.

Balls, now I want one.

Youtube vid of one running in truck

One on Dyno

It's big, it's loud and it really needs a good choice in transmission/rear axle ratio. But think of how many other people have one, huh?

I had a '66 1T PU w/ the 305 V6... what a sweet sound that was. Those valve pans are distinct too.

702 on the dyno... priceless

the Car Craft article mentions that someone actually makes go-fast(ish) parts for the GMC V6/V12... i also saw pics of a few of them built up with goodies like 6-71 blowers on them somewhere..

they also show a few different trans options..

Ooh... 6-71 blower and a nice 6L90E. That'd be one nice combo.

http://www.youtube.com/watch?v=puJaDfB4UFM

Does look like two V-6s.

http://thunderv12.com/

Blastolene Brothers used one in this.

http://www.blastolene.com/b702_f.html

I have seen one of these in a custom truck at the Mobtown Greaseball in Baltimore Maryland... Interesting engine.

I've heard of them and I've always wanted one...

http://www.6066gmcguy.org/TwinSix.htm

Neato stuff there.

Electrical stuff? What electrical stuff. Most is the same as the big V6's. Bear in mind GMC built V6s up to 472 displacement. The V12 was actually based on the much smaller 351 V6.

And here is the truck I saw this engine in...

I know it is only related by youtube cross linking, but I need to have one of these! If that much chaos can come across an old vhs put on youtube, I bet it would corrupt my soul in real life.

V-12

noddaz wrote: And here is the truck I saw this engine in...

Help me understand where the transmission goes, por favor.

Meh an old relic with only historical value.

JohnInKansas wrote:

noddaz wrote: And here is the truck I saw this engine in...

Help me understand where the transmission goes, por favor.

It looks like in that picture that the engine and transmission are sitting in there backwards. If you look down low in front of the engine it looks like you can see the transmission pan. So does that mean it's FWD?

only historical value? Its just 2 v6's together. Lots of possibilities for ho up parts. And its awesome. I love the stuff people are doing with weird oddball gigantic engines in hotrods... like blastolene. The engine isn't hidden under the hood, its an artistic element. The big old engines have a style all their own. I'd RUN past a dozen $50k 350 chevy cars to look at a POS running this engine.

I really want to pick up one of these old pump engines, put a 13 speed behind it, and build something ridiculous.
http://www.youtube.com/watch?v=B6ZbfbE04R0

In reply to 16vCorey:

It may have a completely backwards drivetrain with a boat V drive. especially possible if it used an old jeep rear (among others) that had an offset pumpkin (also pretty easy to build from a standard rear).

andrave wrote: only historical value? Its just 2 v6's together. Lots of possibilities for ho up parts.

And probably less powerful than a modern V6 while less efficient than...anything you can get in a roadgoing vehicle these days. And this is one of the ugliest engines I've ever seen so it doesn't even look good (Edit: The tarted-up ones above aren't an eyesore (not sure about the one in the hot rod), but still look like they belong in a tractor). There are many better V12s out there and plenty of V8s that would still outperform it.

JohnInKansas wrote:

noddaz wrote: And here is the truck I saw this engine in...

Help me understand where the transmission goes, por favor.

John this might help:

I'm pretty sure this is the same truck I saw at the NSRA show in York last summer. I'll have to see if we took any pics of it.

Andy, don't torment yourself with this engine, unless you are ready to build something really crazy. Then I'll encourage it.

Wasn't Sperlo looking for an engine to put in his go kart?