never seen it
 

never even seen one in person, nevermind watch one run.

how rare were they?

i herd of it through this forum...but there no way these were an optional engine in our trucks right?

Re: never seen it
 

Idles low enough. For some reason I was waiting for it to sound off like a jet engine but then it was all quiet??!!

Re: never seen it
 

there's actually one on this forum that is building one intoo a truck .
hes used to work on them in his younger days , they where used in trucks (but the big rig type of trucks ) and as irrigationpumps and are basicly two gmc V6 engines cast together .
take a look on google theres plenty info about them still

the blastolene bro's made a custom car with one of those engines too

Re: never seen it
 

I posted pics of a GMC V12 that was at the Texas Early Days Tractor and Engine show this past fall in Temple. As mentioned above, they were used in big trucks and as stationary engines such as irrigation pumps and such.

Re: never seen it
 

The owner started it a few times. it was not super loud. I am sure that that is because the cams used in them did not have a radical amount of lift or duration. I had a 468 BBC that was louder when I uncorked the headers. Still pretty cool for thw "WOW" factor of a V12.

Re: never seen it
 

Some how those two small carbs look out of place . First one i have seen .

Re: never seen it
 

Here's the thread linked just below of the build on here :cool:

http://67-72chevytrucks.com/vboard/s...d.php?t=254111

Re: never seen it
 

G.M.C.made their own engines in the 60's/70's.If you bought a new G.M.C. truck in the 60's with anything bigger than an I-6,you got a V-6---305,351or larger,up to the 702.G.M.C. also sold their own diesels.
The 702 is a combination of 2 351 blocks.4 seperate heads,4 exhausts manifolds,2 intake manifolds,2 carbs and a special dual distributor.Note only one water pump,because it is one of the highest volume pumps made.
702 in video appears to be on propane and for use in big trucks.702 in pictures runs on gas and is set-up for stationary use.
Designed for use in G.M.C.'s big trucks like cab-over type over-the -road haulers.
U.S. govt. used these 702 engines in the big trucks that hauled I.C.B.M. missiles in the early 60's.
I have a 305-E and a 351-C and would love to have a running 702.
This site has some more on this motor:

http://www.6066gmcguy.org/

Mike.:gmc2::chevy:

Re: never seen it
 

GMC had V8 offerings back then too, they just didn't build them in house, there was factory installed pontiac engines in the 60's in light duty GMC trucks.

Re: never seen it
 

hey longhornman, about how many of these motor were made?

in either irrigation or in heavy trucks?

love your road trip stories by the way :lol:

i haven't really had time to look anything up, but i would assume these motors were built to make torque, not horsepower. they probably never even spun much over 3000 rpm, if that. :burnout:

Re: never seen it
 

i have nothing on these things... sorry

Re: never seen it
 

Until 1960 and the change in body styles, GMC used bigger straight-6's (261 and 302), than Chevy (235 and 261), but they also used Pontiac and Buick engines. I had a '38 GMC half-ton that used a Pontiac 226-cid flathead six. Larger styles used larger engines. My '58 Chevy truck shop manual also referred to other engines that were used, including Buick V-8's and Pontiac V-8's. These were in addition to the diesels that were offered and used. The '55-second series and '56 GMC had as an option, Pontiacs' 287 V-8, then followed up with the 347 in '57.

I guess that was the lure that GMC had, the availability of larger engines in the same body, plus a slight change in styling.

Re: never seen it
 

GMC produced a large gasoline-burning V12 from 1960 to 1965 for trucks, the "Twin-Six"; it was basically GMC's large-capacity truck 351 V6, doubled, with four rocker covers and four exhaust manifolds. 56 major parts are interchangeable between the Twin-Six and all other GMC V-6 engines to provide greater parts availability and standardization Its engine displacement was 702 in³ (11.5 L), and while power was not too impressive at 250 SAE net horsepower (190 kW), torque was 585 lb·ft (793 N·m). It was possibly the last large gasoline engine used in heavy trucks in the United States.

http://jonthecomposer.com/WEB/WEB%20..._702_redsm.jpg