While all truck-related attention today is on General Motors’ launch of the all-new 2014 Silverado and 2014 Sierra, let’s take a trip down memory lane and pay the 1960s a visit — when GMC, then an individually-functioning division (rather than a brand) of General Motors, debuted the first V6 pickup engine in history, and one of the very first V6 powerplants produced by an American company.
The unique 60-degree six-banger, offered exclusively by GMC through most of the ’60s, started at a displacement of 5 liters and made 220 lb.-ft. of torque and 120 horsepower… compared to the 305 lb.-ft. and 285 horsepower, and undoubtedly much higher fuel economy, produced by the new 4.3 EcoTec3 V6.
GMC’s 1960s-era 5.0 V6 featured aluminum pistons for improved cooling as well as a stout crankshaft and bearings designed for superior durability. The engine was available in various sizes of displacement, including 5.8L (354 cubic inch), 6.6L (403 cubic inch) and 7.8L (476 cubic inch) versions, later spawning a 7.1L (433 cubic inch) variant with enlarged crankshaft journals and a 10.4L (635 cubic inch) 60-degree V8 with twin balance shafts using the same general architecture as the 305. There even was a monstrous 11.5L (702 cubic inch) “Twin Six” V12 which was basically two 5.8s placed end-to-end with a common block and crank. A diesel-burning version was called the ToroFlow.
“The family of V-6 engines introduced in 1960 was designed to last, and I’ve heard of some owners going more than 450,000 miles on the original engine,” said GMC truck historian Donald Meyer. “They had really high torque and pulled loads well. GMC engineers know how to build durable, reliable engines that never quit.”
Sounds a lot like the new (and oh-so-torquey) base 4.3L EcoTec3 V6 engine in the 2014 Silverado and Sierra, doesn’t it?
Comments
I really want that Twin-Six
I wish I had a dollar for every 305 V6 I changed oil in.
I also loved the warranty engines. GMC used they put plaid valve covers on them. Today collectors highly prize them.
We get customers with the 12’s today as they love to get these and but them in street rods. Not fast but they may a good reliable and cool looking engine.
Now if GM could have adopted this smoother 60 degree design for use in the 70’s fuel crunch years instead of bringing Buick’s rude crude uneven firing 231 V6 think how many more happy customers they would have had up to the throughout the years.
Were these engines used in their light duty vehicles or just medium & heavy duty?
I’ve never heard of this engine line.
I thought GMC just used Chevy engines.
In the 50’s they also used Pontiac & Oldsmobile V8s.
GMC advertises “Professional Grade” and they are just rebadged Chevrolets but 50-60 years ago they actually were professional grade compared to Chevrolet.
They were used in light, medium and heavy duty applications.
“when GMC, then an individually-functioning division (rather than a brand) of General Motors, debuted the first V6 pickup engine in history, and one of the very first V6 powerplants produced by an American company.”
GM should go back to running all their brand as almost individual companies
That would be nice, if GM could afford that again.
We now have less innovation and individuality between brands.
ben saying this for years auto makers are being lazy
Nothing to do with “lazyness”. I too appreciated the individuality or the various GM divisions but the world around GM was changing.
The biggest problem with the individuality (engine wise) between brands was the cost once government got involved. The EPA certification process was the death knell for the individual engines. Each particular engine/transmission/axle ratio combination withing weight classes 500 pounds apart made individual engines between divisions a very expensive process (too expensive).
And as far as the big GMC V6 goes, it was an overbuilt engine for pickup trucks. In 1964, GMC introduced a cost reduced model with the Chevy inline 6. I’m sure it was a result of the price being uncompetitive with other similar 6 cylinder pickups on the market because of the greater production cost of the heavy duty V6. By the late 60’s, you couldn’t get the V6 in a pickup anymore. And eventually the V6’s went away in the big trucks too, replaced by Chevrolet engines. (cheaper to produce and easier on fuel)
The 1973 oil embargo also helped the V6’s to disappear. And to my previous point, the EPA was setting sights on bigger trucks by then too. The surface to volume ratio of the short stroke V6’s was the reason they used more fuel than other similar sized engines and made them dirtier as far as carbon monoxide and unburned hydrocarbons were concerned. International designed the MV series of V8’s to replace the small V engines because of emissions and Ford phased out the FT engines and replaced them with 385 series V8’s for the same reason.
Make that “oil embargo hoax”. Also, that v-6 was definitely common in their pick-ups.
You forgot to point out that CAFE requirements have practically ended any new engine development in this country,.
It wasn’t just that those V-6 es used more fuel. They had a tendency to inhale prodigous amounts of oil as well. Large pistons allow more oil to drift up from the crankcase. But they were definitely overbuilt, and they had a host of other issues as well. They could pull a tank, but they offered no performance in the way of speed, which was deadly in the performance happy 60s. In the larger trucks you would only be doing 35mph by the time you hit 10th gear. That led to folks over revving them on the highway, which then led to many early rebuilds. It isn’t hard to understand why these engines disappeared. Now if they had shown up in 1950 …………………
Do you have any more pics of the truck that you showed the fender emblem above on? Its a concept design that never made production
I believe that was one that someone had custom made. The GMC trucks did not have the option of the double chrome lines on the custom cabs. Those were on Chevy Trucks only, the GMC offered a single chrome strip down the side of the body and this came with a chrome V-6 logo for the hood instead of the standard painted one.
I, too, am intrigued by the fender emblem. It definitely looks like a prototype GMC factory emblem. Does anyone know where this photo came from? I’d love to see some concept photos of the 60-66 GM trucks.
I have a 62 GMC fleetside with the 305 V6. Runs great looking to change it out with a V8 during some restorations. Is the old motor worth anything??? Thanks
you are an idiot
Actually the writer has some of the displacements wrong. The other sizes besides the 305 were 351, 401 and 478. Later, the 478 crank was used in the 351 to produce a 379 and the 401 with the 478 crank was a 432. There were diesel versions of the 351 and 478 as well as the V8 version of this engine at 637 cubic inches. The 637 replaced the V12 in 1966.
These were a way overbuilt and designed engine that is probably the most heavy duty gasoline engine ever produced. I am fortunate enough to have collected a few and owned several more over the years.
You cannot compare the 305 V6 to the new 4.3L ecoboost. The former would out pull later like there is no tomorrow. The 305 had power right from idle just no RPM!
I had a 68 with the 305 v6 it was a 4wd ,456 rear end’s,4speed,ugly gray paint and had 2 cherrybomb muffler’s on it.that thing had so much torque I used it to pull tree’s and hedge’s on my property.people called it the tank.
Hello everyone,
I have a1966 Gmc 1000 2 wheel drive pickup with the 351E V6, engine #000414. and SM 420 4 speed transmission. The engine is in very good shape but I have an opportunity to swap the engine with a professionally built Chevrolet 348 V8. The mechanic is tellin gme tht he believes the front clip has to be replaced to accept the engine. My quesstion, will the 348 motor mount lign up with the current [side] motor mounts of the V6? Also, will the bell housing from the V6 bolt to the V8? Any help would be much appreciated
I have a 1967 C70 Chevrolet dump truck with the V6 401. It has a canister near the oil filter housing mounted on top of the fly wheel housing. The top screws off and a cylindrical 2 inch diameter filter is inside of it. I have no idea what this housing filters. I think it vents crankcase fumes and oil mist back into the crankcase or externally to the atmosphere. Any info would be appreciated. I could use some exhaust manifolds if anybody has any. Thanks.
My 67 C70 has the 401 I believe. I am putting it on the road. I have to learn how to shift the 2 speed rear end. Directions are on the drivers sun visor. It says only pull the red knob when accelerating. Does anyone know where to get front brake drums for my C70? They are 15 X 3.5 with inboard mount 5 bolt to the hub with a 10 inch pilot hole. It says Centrifuse on the brake drum with a number 85781. It is a hydraulic brake system with the dual Bendix Hydro Vac booster. No one seems to have these brake drums for the front. I replaced the rear brake drums 25 years ago with a Webb brake drum. They are still like new cause I have not driven the truck much. The vehicle gross weight is 31,000 lbs. Under the vin it says DD. What does the DD stand for? Thanks.
Do the valve seats have to be replaced on the old V6 to run todays no lead gasoline?
I have a 1970 GMC pickup with a 305ci V6 motor in it and I can not find the exterior emblems or decals for. Nor can I find the interior emblems or decals. Can yall help. Maybe recommend a place.
I have a 1960 GMC 4×4. Anybody have an idea to how many of these trucks produced? Any information links would be greatly appreciated.
I can’t answer your question but a friend has a book of GM production. My ’65 Chevy K10 was one of about 1200. There weren’t many 4×4’s in the early to mid 60’s.
would you believe my 67 C70 dump truck with a V6 401M had a two barrel carb Stromberg W3A I think that did not have the accelerator pump throat holes drilled out. The truck had 77,000 miles on it when I got it in 1990. The gas would squirt up to the top of the carb causing backfiring. It was a yellow county salt truck in WI before a farmer bought it. The carb had the original little round tag on it.
I’m looking for the bolt on screw-on oil filter bracket was made for the v6 between 1967 to 1972 if anyone has one I will purchase it! Thanks
My 67 401 V6 magnum on a short bed dump truck frame GVW 31,000 lbs only gets about 7 MPG when empty. It has an empty weight of about 12,000 lbs. I usually have it loaded to 27,500 when hauling gravel. It probably gets less then 4 MPG loaded. It has a 5-speed manual trans with a 2-speed electric shift rear end. 4 high and 5 low seem to be the same gearing. Top speed is about 60 MPH. Brake drums are no longer available for it. Was thinking of swapping out axles for more modern axles with available drum brakes. Anybody ever done that? I also need a windshield for it. Will a pickup truck windshield work? The cabs of 1970s medium trucks look similar to my 67 except they have a fiber glass flip up hood.
I’m assuming you have a 70 series or an 80 series with that GVW? Those used the commercial cab which does not use the same windshield as the pickups. Some of the commercial cabs had two piece windshields and the cab was produced until 1988 or so.
Changing axles is a possibility. The thing I would most worry about is steering linkage compatibility (pitman arm to steering knuckle) and geometry on the front axle.
The rear would be more straight forward. Newer diesel axles are typically geared numerically lower as the diesels are governed at lower RPM’s.
I have a ’68 80 series dump truck with the 478 Magnum. Best I get is about 4MPG average although the trip to the pit is a short one so I have more idle and low speed time. My truck was originally geared numerically high to push snow on the highway so it tops at about 55MPH at 3000RPM. I don’t like revving it past that even though the specifications rate the HP at 3700. I’ve considered a rear axle change to get rid of the wedge brakes and gain spring parking brakes but the current set up works great. The truck only has 32,000 miles so nothing is worn out and I tend to baby it anyway.
My 5 speed is the same apparently as yours. Fourth and fifth are close. The shift pattern says run fourth low, then fifth low, then back to 4th high and then 5th high. To be honest, I seldom use low even at 30,000 plus pounds. Between the 478 and the gearing, it handles everything easily in high range. I do have an OD 5 speed and a 4 speed OD auxiliary transmission. I may try one or the other to slow the engine down at highway speeds.
I always see the 478 V6 on the drop-down menu when trying to get parts. They never show the 401 V6 magnum. I think school buses may have used the 401 V6. I bet the school buses would have the same front brakes as my 67 C-70 Chevrolet dump truck. Seals, bearings, and brake shoes are also hard to find. Not sure if your truck has tandem rear axles. I think my truck was a county salt truck in Wi. It has quick connect hydraulic hoses in the rear for a salt spreader attachment. The controller is still in the cab. My C-70 also came with very heavy steel snowplow that was raised with a hydraulic cylinder via a starter motor- hydraulic pump between the seats in the cab. I would post a pic of my truck but the website does not seem to support pictures.
Depending on the size of the school bus, all the V6’s were available. The bus chassis was pretty much the same as the truck chassis so those parts probably interchange.
COST ESTIMATE FOR REBUILD ON A 305-C WHICH IS STUCK??
If you do it yourself you can do it for a fairly reasonable price, but it might take you months to years to collect the parts, you will have to find new old stock on just about everything as it has all long been discontinued. Find good junkyard parts. Or have parts custom fabricated. Usually the better option is just finding a used one in decent shape and swapping them out, even then I would look to get a 305E or 351 Magnum
Things like pistons and rings are almost impossible to find now. Gaskets and bearings still seem to be out there. I’ve been collecting the V6 stuff for over 20 years and have enough spare new parts to keep all of mine running until I quit running. I once bought a set of 305 V6 pistons (030″ over) for $10.00 when nobody wanted that stuff. I think the shipping was more than that lol.
One alternative if you need pistons is have them custom made but that will probably be $1000.00 by itself. See if you can get it free first and if you can it may run.