GM Heavy Duty Motors

June 18, 2001

Someone at PUTC posted a thread about the Old Commercial GM V-6m V-8, and even a V-12.

The C.U. were as followa

V-6 V-8 V-12

305 637 702

351

379

401

432

478

The 702 supposedly had four heads and exhaust manifolds and two intakes. These were built in the 60's to compete with the diesel market.

I WANT A 702!!!

I looked all over the 'net, but can't find anything.

Shaners · June 19, 2001

The 702 V-12 must have been made by taking 2 of the 351 V-6's and (more-or-less) welding the blocks together and putting a crank and cam in them the length of a football field!!!

Kinda the way the 4.3L is a 350 V-8 minus 2 cylinders...

76BBSub · June 19, 2001

Never heard of it, but if you find something out I'd be interested in learning more.

A 702...it just sounds cool!

Jeff

Pastmaster · June 19, 2001

Where they used in Medium Duty trucks? I've seen several old GMC motor's in Old Airplanes. I would assume that they were the only vehicle that could accept a motor of that size. Did you happen to see the size of the bore? It was almost 4.5" long. Talk about huge. The 454's isn't that big...

June 19, 2001

From what C/K man said over at PUTC, they were built for heavy duty applications to compete with diesels. I put another post there to get info as well.

June 20, 2001

Got the link.

http://groups.yahoo.com/group/6066_GMC_Truck

There is some really neat info there. Jeff there was definitely a 702 gas motor withsomething like 240hp and 550pd.ft. of torque.

(Edited by Friz at 8:04 pm on June 19, 2001)

Jpshostr · June 20, 2001

Quote: from Friz on 10:03 pm on June 19, 2001
Got the link.

http://groups.yahoo.com/group/6066_GMC_Truck

There is some really neat info there. Jeff there was definitely a 702 gas motor withsomething like 240hp and 550pd.ft. of torque.

(Edited by Friz at 8:04 pm on June 19, 2001)

I wouldn't exactly call 702 cubes turning out only 240 horse a powerhouse. What kind of truck would you put this thing in?

76BBSub · June 20, 2001

Not to knock the old stuff (me being the Classic Forum moderator and all) but a new 502 crate motor would make more torque than that...

That being said, big old motors are still cool, I'm going to check out the link just for grins!!

Thanks for the info, Friz...

Jeff

Shaners · June 20, 2001

If I had to guess I would think the V-12 would go in heavy equipment mostly (earth movers etc...). Although there could be some applications for large over-the-road tractors...

Pastmaster · June 20, 2001

I wouldn't exactly call 702 cubes turning out only 240 horse a powerhouse. What kind of truck would you put this thing in?

To make it worse, those were rated using "Gross" numbers, not net or rear wheel like today. So it would be something like 200-220 instead. Can you imagine the mileage? 5mpg best?