If someone with no prior knowledge of General Motors were dropped into their Warren Tech Center somewhere between 1960 and 1964, in the manner of Hertz dropping a guy into a moving Impala in their old commercials, that someone would most likely think of GM as a trailblazing, fast-moving corporation with innovation as its cornerstone. It’s been well-documented here and elsewhere. The Corvair. The Tempest’s “rope-drive” with rear-mounted transaxle. The Buick aluminum V8. Turbocharging. The Buick V6. Left out of that conversation to some extent is the GMC 60-degree engine family, introduced for the 1960 model year. Like most of GM’s other innovations of this heady period, it took the primrose path to obsolescence, but what an interesting path it was.
The V6 was perhaps GMC’s final opportunity, at least in the light truck line, to show the world that it was not just some tarted-up Chevrolet, and early advertisements beamed with pride. Colorful illustrated ads and comprehensive text extolled the benefits of this truck-only engine, which also included a V12 “Twin-Six” for the heavier models. There are about a dozen ads in my collection that feature this engine family in some way.
I’ve been studying the 60-degree GMC for weeks now, watching rebuild videos on YouTube and reading articles, and I’m fascinated by just how overbuilt it is. The lightest V6 weighs over 700 pounds, the Twin-Six nearly 1500. The connecting rods and pistons are monolithic. The block is stout; even the front cover is cast iron and weighs a ton. The camshaft and lifters are oiled by their own separate trough high up in the block – the camshaft is basically swimming in oil. The valves feature positive rotation. The bearings are huge. By most accounts, these things were built to pull and outlast a house; unfortunately, a house might have gotten better fuel mileage if it had had a motivating force. By many accounts, poor fuel mileage was the engine’s main shortcoming.
The crown jewel of this engine family, as I mentioned above, was the “Twin-Six,” which displaced a staggering 702 cubic inches. A late effort to out-Diesel a Diesel, the Twin-Six was about the only thing to make the V6 look efficient.
The Twin-Six earned its own V12 badge (where can I find one of those?) and has found some moderate popularity as an off-the-wall hot rod engine. Wearing four cylinder heads and two carburetors, the Twin-Six produced a mere 275 horsepower at a low 2400 RPM, but a staggering 630 lbs./ft. of torque at only 1600-1900 RPM. Like the V6, the Twin-Six was not built for revving; according to 6066gmcguy.com, the maximum recommended engine speed was 2400 RPM – the power peak. Even the V6 was all done well before 4000 RPM.
The ads touted greater fuel economy. Compared to what? Anecdotes from the internet seem to agree that mileage was dismal. Regardless, the Twin-Six is a fascinating engine from a fascinating period.
Most advertising, however, focused on the V6, which was offered in 305, 351, 401, and even 478 cubic inch variations; later “Magnum” versions offered a few more displacement options. The 478 had a monstrous 5.125 inch bore, so the bore spacing was unreal, as you can clearly see in the picture below. GMC eventually converted the V6 to a 637 cubic inch V8 with a balance shaft (remember that a 60 degree design is not optimal for a V8) to replace the Twin-Six.
Another selling point of this engine family was the well-designed cooling system; this ad may not actually prove anything, because I’ve never seen another engine set up to resemble a fire hose, but GMC claimed that there was no more than four-degrees temperature variation anywhere in the cooling system. Minimum cooling capacity for any truck with a 60 degree engine was 32 quarts. Also notice that the narrow block necessitated a narrow valley cover, especially compared to the GMC’s interdivisional brethren such as the Pontiac V8.
This 1963 advertisement foreshadowed the move to the blander use of photography as the 1960s elapsed. The last great year for automotive advertising was, in my opinion, 1964 (Pontiac ads illustrated by Fitzpatrick and Kaufman notwithstanding).
The V6 (“ONLY GMC HAS IT!”) was available in the entire GMC line of light, medium, and heavy-duty trucks, with the little-loved Toroflow Diesel variation being offered in some models. I’ve read almost nothing good about those engines, but have no experience with them myself.
GMC still had a few colorful ads up its corporate sleeve in 1963 and 1964. This one illustrates nothing new, just repeating the same claims about superior cooling and oiling, although it does allude to the engine’s burgeoning reputation for durability.
This ad is one of my favorites in my GMC collection. Once again, little new is said, but one of the illustrations highlights the beefy crankshaft, which was cast instead of forged (except for, apparently, the Twin Six). The caption on the bottom right is illuminating: GMC offered “a new pickup at a low, budget price. Its thrifty inline engine has a simple design that assures economical operation.” This well-hidden nugget of information would become more overt the following year.
By 1965, things began to change in advertising and at GMC. First, the advertisements transitioned to photography almost exclusively, with bland backgrounds and copious text. Second, GMC began to pictorially advertise a standard Chevy straight-six. Apparently, dealers wanted a lower-cost alternative to the V6 that they could use as a “price-leader” to make them more competitive with the low-priced three.
Here’s another ad from 1965 discussing the merits of the inline-six.
Most ads, however, still highlighted the good qualities of the V6, including its durability. Also advertised was GMC’s use of a printed circuit dashboard, apparently the only one in its field.
I’d love one of these trucks simply for the emblem on the hood. There are still a couple of V6 diehards out on internet forums; some claim gas mileage up to 16 or 17 MPG, while others claim 4. Like anything else on the internet, your mileage may vary.
If nothing else, this ghost-like image of the GMC’s major mechanical components is interesting.
My personal advertising collection contains no GMC V6 ads for 1966 and 1967, and only one for 1968. This ad shows the V6 in the picture, but does not mention it at all in the text. Although GMC didn’t wind down V6 production until 1974, the writing was on the wall when Diesels and Chevy V8s became totally reasonable alternatives to GMC’s engines. The Chevy V8s (both big block and small) are without a doubt great engines, some of the best V8s in American history, but their proliferation ended a truly unique period for General Motors. The “Chevification” of GMC was but one step in the General’s eventual homogenization.
Although the 60 degree GMC is a somewhat forgotten and still controversial engine family, its quirkiness combined with the handsome styling of ’60s GM trucks has to put this truck high on my list of “someday” vehicles. I might have a hard time finding engine parts, but I’m sure that unique exhaust note will put a smile on my face, at least as long as I can afford the gas.
CC 1963 GMC Pickup: The Very Model Of A Modern Truck V6 Engine PN
Engine History: GMC Twin Six V12 – 702 Cubes, 275 hp @2400 RPM, 630 Lb.Ft. @1600 RPM PN
Great article. The first thing that caught my eyes: the short heavy V6 was entirely behind the front axle. Those pickups must have had superior traction and handling, and somewhat easier steering.
It weighed a bit over 700 lbs, which was significantly more than the Chevy six.
I guess the selling point must have been that the longevity would offset the poor fuel mileage. As long as you had the money to keep them fed, these beasts must have been tough to kill. A noble experiment to distinguish GMC from Chevrolet trucks, but easy to see why it ultimately failed.
I’d say V6’s primary target was the medium/heavy line. That Target was pretty well hit; V6 sure beat any “truckized” passenger car engine.
As to the pickup line, I would guess that was mostly about the prestige and especially economy of building engines in-house on a line that’s already being “paid for” by the heavier applications.
The pickup engine wasn’t such a hit as it might have been 10 years earlier. The target moved. The new ideal in pickup truck driving characteristics was about being “snappy” and nimble, with car-like performance, rather than the old emphasis on slow rugged hauling capability
The Corvair. The Tempest’s “rope-drive” with rear-mounted transaxle. The Buick aluminum V8. Turbocharging. The Buick V6. Left out of that conversation to some extent is the GMC 60-degree engine family, introduced for the 1960 model year. Like most of GM’s other innovations of this heady period, it took the primrose path to obsolescence,
I never really thought of the GMC V6 in this company, although the Buick V6 did go on to have a very long life. The GMC V6 was a rational and logical solution to the very real necessity of replacing GMC’s very elderly inline six gas engines. What were the alternatives, for an engine that could power a wide range of trucks from pickups to HD models. A V8 is of course the obvious one, but the V6 had a number of intrinsic advantages, for trucks, with a better torque curve and lower max. rpm.
As to the anecdotal remarks about its poor fuel efficiency, I question them. Sure it used a lot of gas, but that was the case for all gas truck engines. Are these objective comparisons, or just subjective impressions. I find it hard to believe that the V6 was somehow less efficient than other comparable sized and power gas truck engines.
As the the V12, it’s primary purpose for existence was not so much in trucks, but as a stationary engine powering irrigation pumps and such. That explains why it was tuned to run at a significantly lower max operating speed, and thus had less max. power. It was a much cheaper alternative to the very expensive Hall Scott engines in such applications, and as such, helped kill off the H-S engines.
A V6 seems to me like a slightly off-the-wall choice, which fit in with the general GM zeitgeist of the time. What other American vehicle had a V6 in 1960? I’m not sure when the 6V Detroit Diesel was introduced, but there couldn’t have been many more than that.
I’ve never understood why a six-cylinder is considered to be a lower RPM torque engine than a V8. I always think of the 300/302 in ’80s and ’90s Ford trucks, and it seems like the 302 always had more torque, although it might have come in at a slightly higher RPM (probably not much) Obviously, camshaft and cylinder head tuning have a lot to do with that.
All things being equal (which they hardly ever are) a six cylinder of the same displacement as a V8 will intrinsically have its torque peak at a lower rpm (meaning, it feels “torquier”). And a V8 of the same displacement as a V12 will have its torque peak at a lower rpm. And a V12 will have its torque peak at a lower rpm than a V16, and so on. And a four will have a lower torque peak than a six. And a John Deere two cylinder beats them all in terms of a fat low-speed torque band. 🙂
Here’s the ratings for 1969 Ford 300 six and 302 V8 (all in gross numbers):
300 six: 170 hp @3600 rpm 283 lb.ft. @1400-2400 rpm
302 V8: 210 hp @4400 rpm, 295 lb.ft.@ 2600 rpm.
Note that the 300 six is already at max. torque at 1400 rpm, and that its torque curve is flat all the way to 2400. Meanwhile the 302 V8 doesn’t peak until 2600 rpm.
I don’t have dyno charts handy, but there’s no doubt in my mind that although the 302 makes a bit more max.torque at its peak, at 1400 rpm (and thereabouts) the 300 makes significantly more.
This is a graphic demonstration why the 300 six is a much more suitable for truck use. I can’t find it now, but some years back we had a COAL series, and the author first had an F150 with the 302, and was very unhappy with its poor torque at typical engine speeds. he then replaced it with another F150 with the 300 six, and it was much improved.
As to the V6 being off the wall, as I said, it was a logical and pragmatic choice, since it was intrinsically more compact, stiffer and lighter than a big inline six, but maintained the superior torque and relatively low max. power peak of a six.
The reality is that the passenger car V8s used in trucks were always a bit of a compromise, as they were tuned for higher power peaks. I drove a Chevy C60 flatbed for a construction company; it had the 283 V8, and that thing had to be flogged/revved mercilessly when loaded. A big six would have been much more suitable.
And I can do the same comparison with the Chevy 283 V8 and 292 six, I’ll dig them up. Needless to say, the 292 had a much fatter, lower torque curve.
GMC had a long history of gas sixes, and they liked its intrinsic characteristics, and wanted to keep them. Configuring it into a V6 was a bit leading edge, but as I said, it was very rational. Why not? There was zero downside.
Here’s the stats and dyno charts of the Chevy 292 six and 283 V8:
170 gross hp @4000
153 net hp @3600
275 gross lb.ft @1600
255 net lb.ft @1600
283 V8 (two barrel)
185 gross hp @4600
150 net hp @4200
275 gross lb.ft. @2600
245 net lb.ft @2600
I can assure you that a 1000 rpm difference in peak torque makes a very real difference in normal driving in a car (quicker response at take-off) but particularly so in a truck, which needs to spend pretty much all its time between the torque peak and hp peak. The lower and fatter the torque band, the more effective the engine will be, as well as more pleasant to drive. And more economical too, as friction losses are much lower at lower operating speeds.
(The 292 six is the dyno chart on the left)
It would be interesting to see the difference in cam timing between the two engines. Since most six-cylinders used one-barrel carburetors and would therefore never rev that high anyway, I wonder if they used an even milder camshaft than the base V8, since even a 283 2-barrel had more lung capacity and could make more use of a slightly “hotter” cam.
Additionally, I would think that most six cylinders had longer intake manifold runner length, which would add torque as well.
As I said “all things being equal, which they rarely are”.
The very long established theory/science is that if you scale up any given engine design, then it will intrinsically have its torque peak at a lower rpm, due to its longer stroke. That’s the starting point. It’s perfectly logical, obvious and intuitive. And is the key reason why almost every big modern truck diesel engine has six cylinders.
Obviously there are some differences between a Chevy 292 six and a 283. Or any two engines of similar displacement but different number of cylinders. You’ve identified some of them.
And obviously, one could design and build a six with a higher torque peak than a V8 of similar displacement, but it would require some significant changes. Primarily a very large bore and short stroke. And then comparing that to a small-bore, long-stroke V8, yes, then the six might well have a comparable torque peak. But that’s not typical.
All things being equal, an engine with a greater displacement per cylinder will be a slower revving engine with a torque peak at a lower rpm. I can absolutely assure you that the intrinsic science behind this principle is valid, and has informed engine builders since the early days of the 20th century.
Try driving a 1.8 L Mazda V6 and a comparable 1.8 L four. The difference is stark. The switch to a Harley 1.8 L twin. Starker yet.
This was a real issue back when Henry Ford brought out his V8 in 1932. It was a well known fact that although it had 5 more hp than the Chevy six, it had the same torque (130 lb.ft) but that came in at 50% higher rpm. The Chevy six was actually a much better alternative for most normal driving, although the Ford’s lighter weight offset that some.
The 1933 Ford B four had only 200 cubic inches and made only 50 hp, but was well known to have its torque peak at a much lower engine speed, which made it very brisk at low speeds:
There was a real comparison in Rod&Custom Magazine in the ’70’s. Harrahs let them road test 2 ’32’s, I think a B roadster and a V8 Cabriolet, and they included some gentle acceleration tests and a drag race. The B came off the line best and then lost ground to the V8, and the B also showed a spurt forward gaining on the 8 at each shift, with the 8 then gaining at the higher revs in each gear. Pretty much what Fred suggested. I’ll try to find the date of that magazine…it was a real goody.
The same thing also applies to Ford’s flathead six that came out in 1942: it had less displacement than the V8, but more torque and at a lower engine speed. It was considered to be a much better performing engine all-round than the flathead V8 which required more rpm.
I could go on. The little Ford V8-60 was notoriously weak-chested when it came to torque, compared to say a Willys flathead four of the same displacement, as an example.
Another data set, from the 136 CID Ford flathead V8-60 and the 134 CID Willys Go-Devil flathead four:
60 hp @4000 rpm; 96 lb.ft. @ 2600 rpm
60 hp @3600 rpm; 105 lb.ft. @2000 rpm
Thanks for taking the time to post up the data and discussion. This is an argument that seems to come up every once in a while online – and it often turns into a “what oil do you use” type of argument, meaning there’s often a whole lot of posturing without much consensus. 🙂
I suppose the 305 GMC, with its huge bore and medium size stroke will inherently rev slower due to its comparably heavy reciprocating assembly (at least per cylinder, if not total weight), at least when compared to something like a 305 Chevy.
This is an argument that seems to come up every once in a while online – and it often turns into a “what oil do you use” type of argument, meaning there’s often a whole lot of posturing without much consensus
I beg to differ. It’s not a matter of opinion or belief.
It may be difficult to show convincingly with engines of relatively similar size. But take the extremes, and extrapolate from that:
Think about a small Honda 4-stroke motorcycle engine that develops its peak hp at some 13,000 rpm, and its max torque at about 8-9,000 rpm.
The think about a a really large gasoline engine, such as the 28 L Fiat S76, or any engine with very large cylinders. There’s absolutely no way that you can get a 28 L four to rev to 13,000 rpm, and have its torque peak at some 8-9,000 rpm. It’s simply impossible. And for two reasons:
One: the cubic volume of a cylinder determines how much potential power can be applied to it from combustion. And that is determined by how much air-fuel mixture can be admitted. The problem is that when you double the dimensions (bore, stroke) of a cylinder, the volume goes up eight-fold, but the surface area of the valves (and ports) go up four-fold. So the bigger the cylinder, the relatively smaller the valve and port size will inevitably be. That of course reduces power proportionately. Which is of course why bigger engines produce increasingly less hp as they are scaled up. And that means their torque HAS to be made at lower rpm. It can’t not be the case.
Now that assumes that a 28 L four could in theory be able to rev to 13,000 rpm without exploding. If it could, it still would make drastically less hp, and its torque would be at low rpm.
But of course realistically, a 28 L four can’t rev to 13,000 rpm,let alone 2,000 or maybe 2,500, due to the masses of its reciprocating parts.
On the other hand, the smaller the cylinder size, the greater its proportionate valve and port size, which is of course why racing engines favored many small cylinders. They are intrinsically able to be much more powerful per any given displacement.
And because the reciprocating masses are so much lower and because they breathe so much better , they can rev to high speeds, and make much more power. But that also means the torque peak HAS to be at a relatively much higher engine speed.
All of this should be massively self-evident and intuitive, and we can see the examples of it everywhere. Hi-rpm small-per-cylinder displacement engines invariably tend to have high power output and their torque peak occurs at high rpm. Large displacement engines are invariably lower speed engines, and their torque peak is at a lower speed.
I’ve spent too much time on this already. But yes, GMC really did know what they were doing when they designed a big six cylinder engine so that it would have a fatter and lower torque curve than a comparably sized GM V8 engine. It’s not by accident, or a matter of “opinion”. Facts and evidence trump opinion.
Just don’t even start about engine oil…:)
GMC was probably getting killed by International, which had two series of modern V-8s ranging from 4.4L to 9.0L. Ford had also come out with its Super Duty truck-only V-8s in 1958 ranging from 6.6L to 8.8L. GMC had been getting by with Pontiac,Oldsmobile and Chevrolet V-8s, none of which were designed for truck use.
International published a booklet that compared their “SV” V-8 gas engine family to the GMC V-6. Of course, International’s engine was designed “better” in every way than GMC’s.
GMC had been getting by with Pontiac,Oldsmobile and Chevrolet V-8s, none of which were designed for truck use.
That’s only in the pickups and some light duty trucks. In the medium and HD trucks, GM had two families of inline gas sixes, the smaller 228-302 CID family, and the big 426 and 503 CID units. The V6 (and later the V8 version) was designed to replace both families.
That’s true, and the V-6 was designed to replace all three of those engine families. And sire a 4 stroke diesel, but that’s another story….
I don’t know how common this was, but growing up, our church had a ’57 GMC chassis school bus that had a Buick engine in it. I can’t tell you if it was a 364, but I’m sure it came that way.
From my understanding, Chevy used the Buick 322 Nailhead in their larger trucks in the mid-’50s, and GMC used Pontiac and Oldsmobile V8s in some trucks from 1955 to 1959 (before the V6 was introduced).
I have written before about the International line of V8’s. They were designed for medium-duty use and dropped into light-duty chassis. Thus, they were “over qualified” workhorses. Thanks for you interesting and informative article, Aaron. I started selling GMC’s after the V6 was no longer available.
It sounds like you could write up some pretty interesting stories from the showroom, Thomas.
As I began reading I started to wonder why this engine didn’t see use in passenger cars as the V6 configuration became popular, but then I got to the part about it weighing 700lbs and stopped wondering.
I drove one of these once. Around the time he and my sister got married in the early 80s, my BIL’s father was still running their family farm. I was visiting one day and was asked if I could help out for a minute. My job involved driving a 1960 GMC grain truck from one location to where they needed it. It was the V6 and was a new experience for me. Somewhere along the line the original engine gave up and they bought a GMC pickup that donated its engine to the big truck. I don’t know what happened to it, other than that the old single axle grain trucks were already too small for modern ag by then. But that old V6 GMC hauled a lot of grain over the decades.
Cummins Westport offers big spark ignition engines. Spec’s for one of them:
6 cylinder, turbocharged, CAC
Engine Displacement 762.2 CU IN | 11.9 LITERS
Number of Cylinders 6
Operating Cycles 4
Net Weight (dry) 2,650 lb | 1,202 KG
Fuel Type CNG / LNG / RNG
Aftertreatment Three-Way Catalyst
400hp @ 1800
1450lb/ft @ 1200
Interesting history of the engines and advertisements. I agree that the pre-’65 ads are much more compelling. I’ve never thought of ads in terms of the peak of creativity coming in the mid-60s, so that’s something I’ll have to pay attention to more… however I do recall thinking that the rare examples of illustrated car ads from the 1970s & 80s were quite a treat to see, and certainly stood out from the crowd more (I seem to remember a bunch of illustrated Ford truck ads from the early 1980s, but can’t recall any similar GM or Dodge truck ads).
Regarding this era of GMC truck, I wonder what proportion of the light truck market that GMC held during this era… both in total, and it’s sales relative to equivalent Chevy truck sales. It’s a topic I’ve long been curious about, but have never dug into.
Anyway, thanks for the ad examples here — great to look at and read about them!
I worked on many of these V6’s and a couple of the V12’s back in the day. There were several odd details that caused some issues with these beasts.
The spark plugs are on the intake side of the cyl. head. Typical work trucks would have lots of grunge in the valley between the heads, needed to get the area cleaned out before pulling plugs lest you drop sand, dirt or pebbles down the hole into the combustion chamber.
Mechanical lifters, so get out your feeler gages.
The occasional dropped exhaust valve.
Carbs were pretty crude, the usual stumble and catch on acceleration.
Two PCV valves, located under the valve covers, screwed directly into the top of the intake port. Be careful you don’t break them off. Two styles used, the bigger of the two were aluminum and were usually easy to deal with. The black ones were slimmer and a very hard brittle material. Be very careful with these as they are prone to breaking and very difficult to remove if broken.
Last item was a medium-heavy duty problem. Engine governor used oil pressure acting on a diaphragm mounted on the carb. The oil was controlled by a “spinner” valve located in the oil pan on the bottom of the oil pump. What fun to work on if there was a problem.
The engine was pretty tough, oil leaks were fairly rare. It was more the idiosyncrasy’s
of the design that caused problems. Everyone “knows” how to fix a small block or big block Chevy, this strange animal was a bit baffling.
The big block Chevy was a good replacement.
Sounds like there was never a dull day in the office. 🙂
Water outlets must’ve been easy to break too. I recall they were frequently being hunted.
The 12 had two distributors driven by a common drive unit. At the engine’s rear there was an upright drive unit located where the usual type V6 distributor would be. That drive unit had two 6 cylinder distributors and caps mounted horizontal into it.
I was told by a pretty good GMC man that the distributors were Corvair based. The distributors looked like they probably were raided from the parts bin, so Corvair wouldn’t be surprising. I don’t recall the location of the contact points or how all this was kept synchronous.
I changed a 478 head “in chassis” on a LCF. Only have to do one to not forget it. Lol Then… a piston had to come out.
Another 12 story. I believe it was the owner of the truck who told me, there was a deep excavation going on and trucks were hauling dirt out of the pit via a steep ramp. He said the GMC 12 was the only truck that didn’t need a push up the ramp.
And now we’re in the wrong GMC topic but I just had a flashback. The same GMC service guy, once we were looking over a “fabricated frame” Cracker box, I don’t recall the model. Anyway, he commented that the airbags were prone to burst when loaded heavy and going into a corner, that was the air spring’s demise.
Thanks for this. These V6 engines are something I’ve heard about and that’s about it.
That said, I stumbled upon a YouTube video the other night in which somebody put one of the large displacement V6s from a road tractor in a half-ton ’67 or so GMC. No doubt that pickup had some punch to it.
A few things lead to the demise of the V-6 in light duty trucks. Fuel economy was quite poor, the engines were very expensive to produce, they were heavy, and they were not exactly pleasant over about 3000 r,p,m,’s (remember pickups were geared low in those days and overdrive was rare). GMC added the Chevy straight 6’s as a credit option in the light duty line in ’64 and the Chevy Small Block V-8’s as an option halfway though the ’67 model year. The Chevy engines became more popular than the V-6’s in the pickups, and the V-6 was dropped from the 3500 and lighter trucks in March of ’69. The majority of V-6 pickups used the smallest 305 V-6, but from ’66 to ’68 the 351 was available as an option. Known as the 351E, the light duty 351 featured larger valves, ports, manifolds and carburetor of the heavy duty ‘Magnum’ V-6’s used in the 7500 series and larger GMC’s. These features gave the 351E performance comparable to the larger V-8’s in competing pickups but with a very flat torque curve. Nonetheless, the 351E was replaced by the Chevy 396 in 1968. The V-6’s lasted in the medium and heavy duty trucks through the 1974 model year.
As for the 702 V-12, it was replaced in 1966 by a 637 cubic inch 60 degree V-8 also based on the V-6 family. The 637 was significantly lighter and shorter than the 702 but produced about the same H.P. and torque.
Thanks for the extra details, Bob!
Thanks for the great article! I am biased though, there’s a ’67 GMC V-6 pickup in my garage……
Glad to hear that Bob, now I don’t feel like a lone nut.
I’m the curator of a “final edition” 432 in a ’74 square cab. I don’t know why, just when it came along I thought it should be saved for old-time sake. Haven’t done much with it. I did take the opportunity to fill the tanks to the brim when gasoline prices plunged. lol
That ’68 ad with the “bucket” seats has me asking two questions: One, did GM have a bucket seat option in ’65 or ’66 to match Dodge’s Custom Sports Special or Ford’s Ranger package? And two, was GM the first to have a bucket/bench seat option, where the center seat folded down to become a “console” (albeit one with storage only under the seat and a rather low armrest)? I thought that sort of thing wouldn’t be around until the early ’80s.
I think 1967 was the first year for bucket seats in a GM pickup.
I would love to put buckets in my 1974 Chevrolet Custom 10 (with the 250 6 cylinder, the main draw to this truck for yours truly). Seems pretty impossible with the fuel tank location, so that will be a major project for another time (putting a fuel cell in the bed or where the spare tire is, cutting out and replacing the perfectly good, rust-free floor. I love my truck (which should mean something coming from a Ford guy), absolutely hate the seat.
Here’s my truck, for anyone interested in seeing it.
As someone who’s completely clueless about big trucks, and having read Johannes Dutch’s post on the 2018 Scania R650 and its 16.4 liter V8, why did Scania use a V8 configuration instead of an I6? Packaging? That is, would a >16 liter I6 just be too long for a cab over?
The Scania V8 dates back to 1969, back then with 14 liter displacement. Available in cabovers and conventionals for decades.
Big V diesels (both naturally aspirated and turbocharged) were once highly common, especially among German truck makers. Magirus-Deutz offered V6, V8, V10 and V12 engines (all air-cooled). Benz had V6, V8 and V10 engines. Not that long ago, MAN still offered a V8, and even a V10 at the end of the 20th century.
Scania is simply the last V8-man-standing in the western world of heavy, mass-produced on-highway trucks. Everything else is an inline-6 in that line of business these days (and note that Volvo offers a 750 hp, 16.1 liter inline-6 in their FH-16 cabover).
Thank you for that info, Johannes. On the light duty side, I noticed that GM just came out with a 3L inline-six turbo-diesel for use in their pickups and RWD utes. ‘Autoweek’:
“The new Duramax 3.0 will deliver a solid 277 hp in the Silverado and 460 lb-ft of torque. That peak torque is sustained from 1,500-3,000 rpm, and it hits 95% of that (437 lb-ft) at 1,250 rpm.”
“The Duramax 3.0-liter diesel uses a lightweight aluminum block and cylinder head to reduce mass, though the cylinder liners are iron. That’s still a 25% mass savings over a comparable cast-iron block. The main bearing caps are iron, as well, which protect the engine under high combustion pressures while a deep-skirt block (where the block casting extends below the crankshaft centerline) contributes to the strength. Also adding stiffness, an aluminum lower crankcase extension is attached to the main bearing caps.”
I wish them success and am looking forward to long-term comparisons from owners between it and Ram’s 3.0L EcoDiesel V6.
A 3.0 liter inline-six turbodiesel in a light duty truck, certainly interesting and rare.
VW, Mercedes-Benz and Ram offer a 3.0 V6 turbodiesel in light workhorses. And Ford has a 3.2 liter inline-five. As far as I know, everything else is an inline-four (in that displacement class).
Here’s hoping it’s reliable, in addition to being interesting. After reading MagnumSRT8 Brian’s “COAL: 2016 Ram 1500 EcoDiesel – The Bitter Taste Of Limone” last May I’d like to think that GM would have learned from Ram’s 3 liter diesel teething problems in US half tons. I’m also hoping Ram ironed out those reliability issues in the intervening four years.
The 3.0 EcoDiesel V6 (built by VM Motori, owned by FCA) isn’t available in light Euro-commercial vehicles. You can find it under the hood of Maseratis though…
I can only speak for Dad’s ’64 GMC 1/2 ton with the 305/4spd and power steering. Dad, my 2 brothers and I, uncles on both sides of the family, brothers-in-law and various friends over the decades all put a ton of hard miles on “the Jimmy” and the truck was an unbelievably-reliable beast. After 18 years of ownership, Dad passed the truck on to me, and after 14 more years I passed it on to my son. Making the 12 hour drive to Phoenix to drop it off in 2002, it cruised effortlessly at 70 MPH and got 17.5 MPG for the trip(best ever!), and didn’t use a bit of oil either. Legendary drive train, legendary truck.
17?!!! mpg? Wow, as a younger guy in the late 80’s early 90’s I had a ’60 half ton 8 foot step with the later 305E in it. 2V Stromberg carb 4 speed with a 3.73 rear limited slip. I always turned a steady 10 mpg. Great driving truck but the brakes were wimpy for serious hauling. Dual glasspacks that blew out in the first month gave that 6 an incredible low pitched rumble. No car alarm was safe, I left a trail of beeping, sirens and other assorted electronic noise. The 351 and 478 were also available as a diesel. Not the best diesel out there but I like them. I once worked on a D478 that had been stuffed into a pickup. Good times. I always wondered how the gasser would perform with a 4v carb and a lot more compression.
We were just as surprised as you, Erik. I would have never pushed it to 70 if I wasn’t being blown off the road by tractor-trailers. The truck always ran great, so reliable and that ride just capped it off for me.
another fun fact:
factory replacement crate V6 engines had plaid valve covers!
Yes, and they were factory on some pickup engines as well. Most plausible story I heard about those valve covers origin was in 1962 GMC engineers were working on improving the 305’s fuel economy, and their modified test engines were identified by adhesive plaid shelf paper applied to the valve covers. Evidently someone from marketing saw the test engines……
Seems like there was some other “thrifty” engines sporting plaid paint. Maybe 223 Ford? I’m not sure now, it might boil out yet. Lol
And there it is, final printing of the early style Hydramatic.
Back when I was in elementary through High School in the 1970’s and early 1980’s, the school district where I attended school had a fleet of GMC 6000 series school busses dating from the mid 1960’s through the 1973 model year.
The busses in the fleet older than 1970 were powered by the GMC 305 V6 with a 5 speed manual.
The 1970-73 GMC’s in the fleet were powered by the 351 V6 and 5 speed manual with a couple busses having the 4 speed Allison automatic.
These busses were eventually replaced by International S series busses powered by the International 345 V8 and allison automatic.
I have one for sale 305e and transmission runs 600.00