I wonder how you tell which one is which. I just purchased a '62/'63 one tone GMC with one of these motors in it. It turns freely and once checked out I will try to get it running. It has sat for several years.
Look on the front passenger side of the block in front of the head, there is a machined surface with stamped numbers, the first three being the engine size.
I would love to have a V12 too,did find one in a local junkyard 20 years ago but was gone the next time I went back. I seen V12 badges and had to look as I never knew they existed.
I would also like to know, because as far as I know the "A" was the first model of the V6's to come out.
I have one of the twin 6 702s they are cool but low rpm. And like 3 mpg Posted using the Full Custom H.A.M.B. App!
Definately a odd running and feeling engine. It seems more like a stationary engine, that is meant to run at a certain low rpm, rather than a vehicle engine. There is one motor missing in that pic; the medium duty one used in 8500 series trucks. It was 478 or 475 cu in
Well according to this: http://6066gmcclub.com/gmcguy/EngineData.html There was no standalone "305". It has an "A" - "E" designation. Maybe the 305 in the pic is just for representation amongst the family. Makes sense that the "A" is up top because it was the first to kick off the family.
Yes it is a low RPM torque monster. It is interesting to drive. My 305A does NOT like to rev above 3,200 RPM. It feels like it's going to spin its guts out. I can take it to 3,000 RPM before shifting and since I installed some duals with Mellowtones two weeks ago it feels like it really helped it to breathe. It doesn't feel so labored now cruising around. In the future I'm going to rebuild the engine and try a few hop-up tricks (fab headers, raise compression, lighten rotating assy, etc.) just to see what happens. Those who have seen my 61 GMC thread know that i changed my mind on swapping in a SBC. This old jimmy 6 has really grown on me, not to mention the oohs and aahs when people check out the engine. I had lots of Q&A at Viva last year about it.
i have a 478 v6 and a 702 v12, hope have both of them running one day, check out where the pcv valve is located. there is one on each head it screws into the top of the intake ports that are paired, underneath the valve cover....
They are heavy gas suckin S.O.B.s. Heavy pistons with 4 rings. Low rpm's ok not great torque. The best thing about them is the scotch plaid valve covers! I have over 200k behind one. Hope to never have another mile behind one!
i have a 702 i pulled out of a fire truck with 16k miles on it. i had to remove the transmission to be able to lift it with my tractor [int. B414 utility with loader] i'm guessing close to 1500 lbs.
years ago I had a 62 GMC shop truck with a 305 and a 3 spd. I drove the wheels off it. Very dependable, lots of torque, very low rpm, heavy as lead. I put in an overdrive and tall tires. Cruised at 75mph at not much more than about 1500 rpm. Walter
I have a few various Jimmy v6s sitting around. They're neat, but, their time has passed. I hate to be negative, and I have a couple of other odd motors sitting around, but they all share the same burden of being too heavy for the power they make. The best thing I've managed to do with one is pull the plaid valve covers, and have the girlfriend use them as a Jello mold on the 4th of July.
305 A is the pickup motor and the 305 C is the truck engine up thru a 4000 Series two ton, the tag on my 61 4000 says 165 Horse's @ 3800 RPM, we run it at 32/3300 revs all day long, a few years ago I had a haul running 25 miles loaded and back empty grossing about 20,000 #'s it would get between 10 to 12 miles to the gallon, I checked it several times.
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