SO who came up with the GMC V6's???
 

I've been deep into research on these v6's and wondering....what made GM come up with such a different engine? I mean...the thing makes a SBC look like a briggs and stratton. lol And its slower than a 292 I6 by far, but sure has a ton more lugging power. Mine pulls pretty darn good with the 4 barrel and split exhaust, but my 292 with the same mods pulled 10 times faster which makes me wonder....did GM purposely make these to be luggers? Shifting my 292 at 4000 RPM was no problem, but 3000 on this is scary. haha I'm NOT downing the V6's in Any way....just curious as to the engineering behind it. I mean....loaded down with manure I could pull hills at 55 with my 305 no problem and that was with a plugged up 2 barrel. Just thought it would be an interesting discussion. I love my BB V6 and wouldn't trade it for any SBC, but the thing interests me. lol

Re: SO who came up with the GMC V6's???
 

Greetings TJ!

As to who at GM came up with the design of the big block V-6, well, that's information that I don't have, although I also would like to know who that person was. As to the comparison between the 292 I-6 and the various versions of the GMC Big Block V-6's, I'll take the Big Block V-6's any day of the week before I would take the 292 I-6. As many here know, I once owned a 1963 Chevy 30 Series (1 ton) pickup originally equipped with the 292 I-6 which I eventually replaced with a GMC 305 V-6. Now, there will be those here who will disagree with me, but my feeling is that the 292 I-6 was nothing more than a glorified car engine put in a truck, and not necessarily designed to be a truck engine, although GM engineers would differ with me on that point. I know, because my Dad and I had plenty of problems with the 292. When I replaced the 292 with the GMC 305 V-6, those problems all disappeared. Now, having said that, yes, the 292 would be faster on acceleration and rev higher than a BB V-6, but as you indicated, the GMC V-6 will outlug the 292 six ways from Sunday, and all in all is a much more durable engine than the 292 ever was or will ever be. I know you have several 292's in your collection, and that you are very pleased with them. My experience has been the 292 is an engine (along with a few other GM engines) that I do not strongly favor.

On a lighter note, Merry Christmas to all here in the 6066 GMC Truck Club!

Re: SO who came up with the GMC V6's???
 

Thanks for the reply! SO what problems did you have with the 292? The stock 292 that was in my C10 performed nicely even when towing, but I have now gone through and hotrodded it. lol So it doesn't count as a comparison anymore. But yes, I'm pleased with my 292's. But when I came across my GMC with the V6 I was even More pleased because I never had seen one in person before so I had to have it. lol I Love my V6 and like I mentioned...wouldn't trade it for a SBC or anything for that matter accept a bigger V6. But I'm interested to know what you didn't like about the 292's? GM engineers made the 230's and 250's to be more of a car engine and the 292 to be the truck engine of the bunch(not trying to start an argument). The 292 was made the truck engine because of how much taller the deck height was and the much longer stroke to get that added torque which for my experience in a light duty truck served nicely. But in a large C30 like you had that may have been a different story, but I can easily understand why you'd prefer the V6....they were made so bullet proof and durable its crazy. lol Merry Christmas to you to!

Re: SO who came up with the GMC V6's???
 

So GMC was married to GM sister division Pontiac in the 40's and 50's and shared Pontiac's design team for engines. GMC used Pontiac car V8's from 55-57 before Pontiac designed GMC its own variation of the 1958 Pontiac 370 V8 which was a smaller bore 336 V8. In 1959 when Pontiac went to the famous 389 V8, they gave GMC another version of the 336 V8 which had a shorter stroke and was based on the 389 V8's bottom end. This version of the 336 was slightly faster in terms of horsepower over the previous years' 336. During these years, Pontiac engineers developed the V6 as a means of giving GMC its own engine that would give the trucks a distinction from Chevrolet and give them the powerful low end torque they are known today for. You can see the Pontiac engineering influence in the power steering pump and fuel pump designs and the way the V6 intake still sits up on top, separated from the push rod valley vs a Chevrolet fully enclosed design. Everything about the GMC V6 design and appearance screams Pontiac when you compare to the early V8's Pontiac shared with GMC. The V6's are the last stand from Pontiac before GM fully aligned GMC with Chevrolet by say 1966 or so and started offering Chevrolet engines in GMC's. By 1969, the V6 was over with, and the Chevrolet V8 won out over the V6 for cost and efficiency reasons and maybe other things like fuel economy. Not sure if this answers your question any but I believe this to be correct unless Pete, Ed or some of the more knowlegeable and experienced V6 users have anything to add that might shed any more light on the subject of who came up with the V6 design

Re: SO who came up with the GMC V6's???
 

TJ, speaking of acceleration was there a noticeable improvement when you added the 4bbl? One of the drawbacks of the 305 is it has a poor power to weight ratio that's why I prefer the larger displacement V6's. The 305 shares the same block as the rest of the family of 60 degree V6 engines up to the 478, so that makes it really heavy for it's smaller displacement. If you would like to know more on the development of these engines go to Jolly's 6066 GMCguy website and check out the Sept 1959 issue of Popular Science. They actually tested a 1bbl 305 in a prototype 1959 Suburban, being that it was in a smaller and lighter truck the performance was more V8 like of that era.:thumbsup:

Re: SO who came up with the GMC V6's???
 

GMCNUT, for the most you are correct except for a few things. GMC was not married to Pontiac in the 40's & 50's nor did Pontiac engineers design the GMC V6. In the 50's since GMC didn't have their own V8 they chose the Pontiac V8 and of course the was an excellent choice since Pontiac had larger displacement engines, but the Pontiac V8 wasn't the only V8 GMC offered. Trucks that were larger than medium duty used Oldsmobile V8's because of their low end torque. With the introduction of the V6 that was GMC's remedy to be self sufficient by having their own powerplant, As bigger V8's came around the 305 definitely didn't cut it so the 351 was brought out in the light duty line in 1966, an improvement but demand was there for high horsepower V8's so in 67 they brought out the entire line of Chevrolet engines. That was GMC's downfall as it got much easier to produce trucks that were fully interchangeable with Chevrolet, too bad GMC didn't stick with the Pontiac V8's, It wasn't until around the mid 90's that GMC and Pontiac combined to be the same division and that lasted till 2010 when GM killed off Pontiac.

Re: SO who came up with the GMC V6's???
 

Greetings again TJ, and everyone else in the Club!

As to why I disfavor the 292 I-6, I'll try to be as brief as possible. My Dad bought that '63 Chevy C-30 in 1966 with 42,000 miles on the odometer, and at that time with three new pistons in the engine. After putting on another 3,000 miles, he came home with the engine knocking like crazy. This was in 1968, and I was in high school at the time, taking an auto mechanics course, and I diagnosed the problem (correctly I might add) as being a rod bearing knock. We dropped the oil pan, and it didn't take long to determine that the # 1 rod bearing was totally pounded out. We ordered a new (not rebuilt) short block from our local Chevy dealer, and installed it in an unheated garage in 20 degree below zero weather. Now let me tell you that you only worked on it for about 15 minutes at a time, and then had to go in and get warmed up before continuing to work on it on and off until it was completed. Now, as to problems with the new short block, the engine ran pretty much quietly except for the fact as more miles were racked up, and by the time there was 10,000 miles on that new block, that 292 developed a serious case of piston slap. Remember me mentioning earlier that the original engine had 3 new pistons in it when my dad bought the truck with 42,000 miles on it? It didn't matter whether the engine was cold, or at operating temperature, you could hear every piston in that engine slapping merrily away. Dad turned the truck over to me, and when there was about 70,000 miles on that 292 replacement engine, I knew at some point the dam* thing was going to leave me stranded high and dry somewhere. A neighbor had a 1962 GMC 3/4 ton pickup that he had retired mostly due to the body being pretty rusty. I bought that truck and took the 305 BB V-6 out of it and put it in my '63 Chevy. Putting that BB V-6 in my truck was the best decision I ever made, because it was an engine that I could count on getting me from point A to point B and back without the worry that I was going to be hoofing it for help because of an engine failure. So now you know why I have little faith in the reliability of the 292 I-6 and why I think they are best suited for use in a light (1/2 ton) truck, or better yet, a car. That's why I called it a glorified car engine.

Re: SO who came up with the GMC V6's???
 

All the Chevrolet engines whether small or bigblock V8 and sixes were nothing but passenger car engines. Chevrolet even converted the big block V8 into a truck engine by adding an extra compression ring to the pistons, adding an inch to the deck height and there the 366 and 427 trucks engines were born, truly over glorified passenger car engines and GMC was forced to drop their V6 for these junk piles in the mid 70's.:pullinghairout:

Re: SO who came up with the GMC V6's???
 

Big improvement for sure...and that's with the 4 barrel mounted on a 4 to 2 adapter. It should help even more when I have the intake machined to directly fit the carb. The split exhaust made for a nice improvement as well. I'll check out the sight for that issue! Thanks!

Re: SO who came up with the GMC V6's???
 

Man, you sure had some bad luck with that engine. Sorry to hear about that. I never had those problems with mine....at 147,000 and being 50 years old I was doing burnouts and reving my worn out 292 up to 5000 RPM. haha Never knocked and no piston slap, but after an extra 2000 miles put on it, it developed valve train problems. Had no power and would sputter on take off....then it would be fine.....valves were recessed in the head causing them to hang open. Also only had 95 psi in all cylinders and 5 psi oil pressure at idle, but it Never left me stranded anywhere....even with all the problems I encountered during my final drive...she still ran and then died in the driveway. I had to have the valves adjusted at .006 clearance just for it to run somewhat smoothly. lol So yeah, I haven't had quite the same issues, but for an old engine that had a 3600 rpm redline from the factory that could do 5000 rpm I'd say that was pretty good. haha But onto the V6 again, I've never had a smoother running 50 year old engine in my life. This thing never misses a beat! After giving this thing a full tune up and valve adjustment this motor gives me confidence while I'm on the road...which is a plus being that its 50 years old with almost 200,000 on it and only 5 psi lost in the cylinders. They're one heck of an engine. Only engine I have that could idle up a hill lugging down to 250 rpm. :thumbsup:

Re: SO who came up with the GMC V6's???
 

Thanks for all the knowledge guys! :thumbsup:

Re: SO who came up with the GMC V6's???
 

It will definitely make a bigger improvement once you machine the manifold. Many years ago I tried the 4 to 2 adapter and the results were abysmal, the idle would fluctuate and when the secondary's kicked in it would stumble for a couple of seconds.:pullinghairout: I suspect it was a very poor quality adapter that leaked vacuum. All in all there is only so much fuel that you can squeeze in a small opening.

Re: SO who came up with the GMC V6's???
 

Mine idles perfectly, but has the same problem when the secondaries kick in....In 4th if I stuff it to the floor the thing jerks and rattles then clears up. lol I suspected either no vacuum advance or to much fuel for a small opening. But if I quickly ease into full throttle it responds fine. So for now I've left it cause its running so good. But when I get my 66 done I'm gonna get into this one. The improvement was major over the 2 barrel. With the 2 barrel I couldn't even rev the thing past 2500 rpm to shift or it seemed to take a month of sundays to get there...hence why I'm sure that old carb was plugged up. Lugging it into 4th proved faster than reving it. It actually would accelerate faster when I had the truck loaded down, least it sure felt that way.lol But once the 4 barrel went on, shifting at 2500 has been the best rpm. And when I split the exhaust, 2700 is now a good rpm.

Re: SO who came up with the GMC V6's???
 

Talking about who at GM designed the V6, well about 14 years ago a GM engineer that was involved with the development of these engines stumbled into Jolly's site and was quite surprised that there were people that were interested in these engines. His last name was "Cleary" and that's what he went by. He had mentioned early prototypes let loose and scattered easily, more balancing was required. Also the reason for the spark plugs inside the "V" was because during testing one of the engineers went to change the spark plugs and ended up burning his hand on the manifold so spark plugs were relocated inside the "V". Cleary stepped away from that in 1960 or so, he mentioned at that time they were working on Diesel versions. I did save the emails in my old computer, if I get it hooked up I may be able to retrieve it to share with everyone. I also contacted Cleary once myself.

Re: SO who came up with the GMC V6's???
 

If you could find those that would be cool! By the way I read the article...Lot of neat info right there. On another note I've been driving my gmc around in the snow today. lol Even did a burnout! haha Headlights, windshield wipers, and heater all on and no problems. PO took the original heater cables and control panel out cause they were seized up so I settled for a select switch from Napa and manually set the vents so I get hot air. No fogged up windows now(hopefully). lol Need to drive it some more and see how well the defrost works, but it only took a couple seconds for that cab to get warm.

Re: SO who came up with the GMC V6's???
 

Greetings bigblockv6!

I can't help but agree with you, and I too am saddened by the fact that GM discontinued the Big Block V-6 engines. Their durability put all other engine designs to absolute shame, no matter who the engine manufacturer was. By the way, I failed to mention that my old '63 Chevy was traded in for a brand new Dodge one ton pickup. Apparently the original owner of my '63 Chevy was not too happy with the fact that he had to replace 3 pistons in the original 292 I-6, and the fact that they probably were not all replaced at the same time resulting in more than one engine tear down. I'm not sure what engine (V-8 or Slant I-6) the Dodge truck that he bought had in it, but I will go as far as to say that even the Dodge Slant I-6 was a better engine than the Chevy 292 I-6.

Re: SO who came up with the GMC V6's???
 

I found one email in the archives that Pete (referenced) YAY for the Archives and Jeannie.

http://6066gmcclub.com/forum/showthr...eary#post16253

Re: SO who came up with the GMC V6's???
 

That was neat! Thanks for sharing!

Re: SO who came up with the GMC V6's???
 

Thanks Funky61, you saved me the hassle from looking it up for now anyway. I do have one email to look up where I directly contacted Cleary with some more questions. For now though this is really good:upyes:

Re: SO who came up with the GMC V6's???
 

That was a sad day for me back in Nov 1974 when went over to our GMC dealer to pick up a new light switch for the 68 before my father found out I broke it to pieces, I was only 15. Anyway there was not one Medium duty truck or larger 7500 series truck on the lot with a V6.:banghead: I was quite surprised to see a J-7500 series with a 427 V8 for the first time. Some 6 months prior to that just about every medium duty( at least 25-30 trucks) all 7500 series trucks were V6 equipped, my impression then was the V6 was alive and well and they had no problem selling them off. Funny thing was in November there was still quite a few V8 74 medium duty trucks left over with the mix of 75 models.

Re: SO who came up with the GMC V6's???
 

Would have been nice if they kept the V6. But the problem is every darn person has to have that stinkin 350. And because of them, guys like us who want to keep the v6 almost can't because parts are getting more and more scarce by the day. It makes me upset when I see people on forums that have a really NICE gmc with a good running V6....and what's the First thing they say..."I'm gonna swap it for a 350 and th350" Its like Really? REALLY? You couldn't have bought a Chevy and gone cheap on that? I don't know, its just sad to see perfectly good engines go to the scrap yard cause people don't think they are worth anything.

Re: SO who came up with the GMC V6's???
 

I've always said that the sbc 350 is a major national obsession :pullinghairout: When these guys talk about doing this swap they think it's like something real special, there are so other many alternatives today like the newer GM LS engines. I like the idea of just going to a larger displacement V6 specially 401 and up and there you have a substantial power increase and something that's different than that ubiquitous generic bowtie powerplant:lolsmack2:

Re: SO who came up with the GMC V6's???
 

I hear ya! Lotta people are so stuck on "Best bang for the buck" "If it ain't cheap it ain't worth it" and all that stuff. Its like really....why do you need to go 0 to 55 in 2 seconds? My 305 pulls me to 55 no problem...not as fast as a 350, but it still does effortlessly. And sounds so dang good to! lol

Re: SO who came up with the GMC V6's???
 

The GMC V-6 family of engines was designed in the late 50's to replace the two series of GMC manufactured straight 6's along with the 'borrowed' Pontiac and Oldsmobile V-8's. The V-6 idea was actually very rational as the majority of truck engines at the time were 6 cylinders. A 60 degree 'V' design was selected for compactness, 120 degree firing intervals, and a short strong crankshaft. The engines were very 'oversquare' (large bore, short stroke) to provide flat torque curves and low piston speeds. Most every other feature of these engines was designed for maximum durability, like oversized water and oil pumps, large bearings, and high quality materials. For very large trucks and fire apparatus, the basic design could be stretched into a V-12 (later a V-8 as well). It would seem that the design was intended from the start to be made in a diesel version as well.

No question the GMC V-6 was far more durable than any contemporary passenger car/light truck engine, but I think it is interesting to compare the V-6 to contemporary medium/heavy truck gasoline engines. Again, the GMC proved superior to engines like the International Red Diamond and V-401/478/549, the Ford Super Duty 401/477/534, and the REO (later White) V-8's. The GMC's matched or beat those other engines in output but were more durable, lighter (I know, hard to believe!), more compact, and delivered better fuel economy.

Re: SO who came up with the GMC V6's???
 

WOW! Thanks the sharing! Has anyone dynoed these that you know of? I'd be interested in seeing the torque curve. A friend of mine said the main bearings on these were as big as a 7.3 diesel engine's main bearings. I know GM made the toro flow but from what I've been reading it wasn't a very good success? There is one for sale about 45 minutes from me for $500. Supposedly runs to. Wow...a GM V6 being lighter than something is surprising. lol Thanks.

Re: SO who came up with the GMC V6's???
 

The main bearing journal got even bigger on 73-74 478M V6 engines, bigger main caps, larger bolts ad just a lot more reinforcing in the main saddle area.

Re: SO who came up with the GMC V6's???
 

Any particular reason why that you know of? Like they weren't big enough already. lol!

Re: SO who came up with the GMC V6's???
 

Nothing that I heard of but in 73 the whole line of V6 engines other than the 305(the 305 originally was slated to be discontinued for 72 but they decided to keep it going) went through upgrades. The gas engines only used 2 bolt main yet the Diesel versions had 4 bolt mains, actually cross bolt mains. Possibly there may have been some bottom end failures with 478's in the 7500-8500 series trucks, I have a 73 478M and the main caps are so much larger and contour better with the bottom of the block. I'll takes some pics of both the new style caps and old caps for a comparison and post them sometime this week.

Re: SO who came up with the GMC V6's???
 

I worked at GMC Truck and Coach in Pontiac beginning in 1974 as a co-op student, but by that point in time, the area of Plant 2 along South Boulevard where the V6 and V12 were made was not being used much, maybe only for service parts. The part of the plant where the engine line was located was called building 29. All of the tooling was shipped out around 1977 to make room for the GMC Motor Home in building 29. The Motor Home had been built in Plants 3-4-5 on the other side of Woodward, and was relocated so the G-van could be built there. I don't know where the engine tooling went.

I reviewed the James Cleary email from 2004 and I only recognized one name from the list of people that helped design the engine. I have a friend who told me that his father is listed on one of the patents for the engine (last name is Sherrick).

Dave Boboltz, Waterford MI, 1964 K1002 305E

Re: SO who came up with the GMC V6's???
 

Dave, after the tooling was shipped out were service parts manufactured at a different plant or do you think that was just the final end of the GMC V6. Evidently GMC must of stockpiled a good amount of parts, back in 1984 I looked into buying a new 432 V6 and it was available through the dealer.

Re: SO who came up with the GMC V6's???
 

Big Block V6, that is a great question and I don't know the answer to that. I did send Cleary an email so maybe I can learn more. Or there is another guy who lives nearby who has some amount of historical information (Don Meyer).

I suspect that the tooling went somewhere that would be capable of making service parts. It would be interesting to know where that tooling is now.

Dave Boboltz, Waterford, MI

Re: SO who came up with the GMC V6's???
 

It would be interesting to know what became of the tooling. From what it looks like in the email, Cleary was no longer in the V6 development sometime in 1960. He was not aware of the 379,432 and 637 engines.

Re: SO who came up with the GMC V6's???
 

So here's a question....anybody know why a small single barrel and then two barrel carb were used on these engines? I'm assuming for low end power and fuel mileage? Might be a dumb question, but with the large bore I would have thought a bigger carb would have been used.

Re: SO who came up with the GMC V6's???
 

The one barrel did not work out well with the 305 engine by 1961 the 305D 2bbl engine came in to replace the 305A even though it was still available. 125 net horsepower to carry around that much weight was really underpowered for the 305. The 2bbl brought it up to 142 net horsepower then with more improvements for 1966 to 157 horsepower. Possibly mileage may have been why a 1bbl was used. Originally the prototype trucks used were lighter 1958-59 trucks and the 1bbl version was more than adequate.

Re: SO who came up with the GMC V6's???
 

Ah, Ok. I watched a video of a 305A running...man you could hear that thing Breath. lol I was like yeah....that carb is a bit small. You know what improvements were made in 66? I remember running the numbers on mine with a fellow forum member, and my 305 in my 64 looked to be a 67 series engine. Did the 305E ever come in medium duty trucks? Cause mine had the governed dizzy on it.

Re: SO who came up with the GMC V6's???
 

A new cam along with different count timing chain and sprockets were some of the changes, at some point up to 66 larger valves were used on the 305 engines as well. Medium duty trucks used 305 engines from their beginning in 1960 all the way up to the very last in 1974:thumbsup:

Re: SO who came up with the GMC V6's???
 

:lolsmack2: I should have included this in my previous response. Yes 305E engines they were used in 3500, 4000 and 4500 series medium duty trucks.

Re: SO who came up with the GMC V6's???
 

Light duty trucks too were available with governors.

Re: SO who came up with the GMC V6's???
 

Ah ok, yeah....I had to get a new dizzy cause the old was was frozen up....the governed vacuum pump was seized or something. Here's another question....any particular reason why the compression was made so low?

Re: SO who came up with the GMC V6's???
 

I'm not absolutely sure but from what I recall The idea of having low compression was for achieving low end torque.