Back around 1990 I put a 478 gasoline in a GMC dump truck that had a blown up 305 in it. A guy I knew showed up im my shop and said "Hey I've got one of those engines" Next day he showed up with it in the back of his pickup and sold it to me for 200 bucks. I started looking and saw the dual thermostat housing and knew what it was. Damn that thing was a torque monster. You hardly ever have to shift. Funny thing about it was the exhaust had a low deep rumble that set off car alarms of cars parked on the street

Being a Stealership Mechanic in the Oldsmo-Buick days was a lot of fun. If those things made it past 50,000 miles without the heads flying off, they'd go 200,000. The ones that didn't got a Target Motor, Hecho En Mexico with thicker decks, larger head bolts, and a stronger fire ring design head gaskets. Did I mention Warranty Work Flat Rate sucks?

Among other things I have a running surviving Olds diesel with 230,000 on the clock. It is one of my summer drivers. I also have a 478 Toro Flow that I acquired years ago for $67.00. Might make a good pickup truck engine lol.The dump truck in my avatar has a 478 Magnum gasoline V6.

As the former owner daily driver of a 351 gmc V6 which acted like a 4.3 performance wise with 454 mileage with a stromberg carburetor using a unique carburetor pattern and a floor pivoting mechanically sprung throttle, I must admit this was a depressing engine to find service parts for. It was hard to maintain it really was. I was lucky to have the help I had from the likes of my surrogate father a brilliant body man who held a GM license whose career and financial success peaked in the mid 1980s. That engine line was good but bad because it was ghosted and abandoned.

Adam, I'm really enjoying your engine video series. I've been learning a lot! Thank you.

Great info. The first I heard of these engines was on Steve Magnante’s channel. I never knew that some of those old GMC medium duty trucks and buses had V6 engines, albeit large ones.

It is worth noting that, while the initial Toro-flow diesels were normally aspirated, GMC did offer turbocharged versions of the 478 and 637 later on.

I remember some of these engines. My father worked for Coca Cola at my small town bottling plant and used these GMC trucks in delivery fleet. I recall adjusting overhead lash on the older engines with solid lifters and cam with the engine running and oil flying all over the place. Those were the days.

GM made a huge mistake not putting a water separator in the Olds 350 diesel.

Thank you for covering these heavy-duty V-6s from GMC again. Somewhere, a person called them the 'Hercules' series of engines because of their durability. I particularly like the V-6 478...hitting its maximum torque of about 440 at 1400 rpm....think about that. You reach your maximum pulling power in a truck not many revs above pulling away from the stop sign..

I like your engine video series.

I've been around, and drove a lot of the GMC V6 gas engines, but have only ever seen 1 of the V6 Toro-flow diesels, and it wasn't running at the time. I wasn't even aware that they had a V8 version of that engine. Pretty cool stuff!😉

I live for learning about engines I've never heard of. Just rebuilt my first two stroke last year and it's making me money but only because of people sharing knowledge on KZfaq. Thanks

THAT GIANT V12 WOULD PULL THA GATES TA HELL DOWN THE TORQUE THEY PRODUCED WAS NOTHING LESS THAN INCREDIBLE

I always thought "Loathsome Diesel Stench" would be a great grunge band name. I'm odd.😊

Thank you again, Adam, for sharing these engines with us.

Lots of memories here, from a time when GM was still a very innovative company, sometimes making huge mistakes, sometimes minor ones, but all very interesting. I've loved the sound of these since I was a kid riding to school behind one !! Thanks for sharing. You now need to talk about GM medium / heavy duty trucks with independent torsion bar front suspension in the 1960-1966 period. Really interesting stuff !!

Nothing like the smell of Diesel in the morning.

I got my first GMC V6(a 305 c.i.) while serving in the Navy back in 1985. I bought a former Washington State Forest Service 1963 GMC longbed/stepside. I found probably the last tire ship in Washington(Tacoma to be exact) that would mount new tires onto the original split-rims. I drove that truck from Washington down to California when my ship(USS Belleau Wood) came out of the drydock in Bremerton to return to San Diego. I eventually gave it to my Dad, who drove it form many years up in Northern California The next was a 351 c.i. in a 1962 GMC utility longbed I rescued from a junkyard in Oxnard California in 2000. I ended up finding a fleetside bed for it and even found an early '70s camper that I put on. Whenever I had a long weekend that old beast and I would head east from NAS Pt. Mugu and disappear into the mountains or desert for a few days. Very early I was given a great education in these V6 GMC engines; I learned how NOT to mistreat them and how to keep them running well. The most important thing I learned was not to 'over-rev' these motors. They were designed for low-rpm/high-torgue applications. That made them great for work-trucks. Because of that education I never once had a problem with either engine. I replaced the old points ignition on my '62 with a Pertronix electronic ignition. I also found a nice Holley 'Economaster' 2-barrel carberator. The combination allowed me to get a stable 15mpg with this old beast. I'd love to find another someday.

Sounds! What a treat. That's the first thing to go away forever. Thanks Adam. 👍

Those were low rpm commercial engines when gasoline was still common in big trucks.

Oh the stench of the Olds 350 diesel disaster. It still lingers to this day!! And as a friend of mine calls them, the GMC Toilet Flows

Knew two guys that had the Toroflow in a couple of their trucks they seemed to like them. One of the guys said the difference in fuel cost almost made the truck payment. Having talked with a few mechanics that worked on the Olds diesels the big reason for the head gasket failures was due to the poor grade of bolts used for the head bolts meaning the head bolts would stretch. The quality of the head gaskets was also suspect.

Wow Adam, this is AMAZING info that is not known by anyone, except U...So much to learn for all of us Adamites😮😉👍👏

Thanks for showing such unique engines that I had no idea of! Very interesting.

Adam, your videos are very informative, and your delivery of commentary is perfect. A true "find" on youtube these days. No fancy introductions, just the facts. Thank you!

Would LOVE for you to do a presentation of a hearse. They are a unique and necessary component of vehicle history. Most are Black, some are White, others are Silver, some are even Green. Have seen Red one, which I view as beautiful!!!! Hope you will take the challenge.

I'm really enjoying this engine series. Keep it up. Thanks!

Really interesting great content and presentation.

I have only seen one of these running so far. It was a 478 diesel in a new idea uni system it is a self propelled power unit you could put a corn picker, forage harvestor, and a combine attachment that went onto it. Also if an old mechanic friend of mine is to be believed any auto/truck have more injector pump issues than the same diesels used for ag or marine as you mentioned do to more consistent rpm use.

Direct-Injection was the exception back then, not the rule. Modern diesels almost all have the bowl in the piston because of the DI. Very interesting.

Had a Chevy Caprice station wagon with the Olds 350 diesel, bought it new in 1981, I guess that by 81 GM had worked out the problems with that engine because I had no issues with the engine or for that matter the rest of the vehicle. would give 33 MPG on a trip, with only 105 horsepower you did have to exercise patience on a hill however. Ran great until I traded it in with 90K miles.

I have a number of original shop service manuals for these very GM & Detroit engine from my dad, who, after years of being a heavy equipment operator & OTR truck driver, went into being a diesel engine tech back in the late 70’s… myself from end of HS into college, went into construction/framing, followed suite by the mid 90’s, working as a cert’d auto tech for gas & diesel, performing repairs for anything & everything.. then, power tool repair/rebuilding to machining. By oh, ‘07, went to OTR and local trucking, then plumbing, then HVAC, then HAZMAT fuel tanker trucking.. since covid, back to auto tech, gas/diesel & all things electrical… I have auto/truck service tech literature from oh, 1903 to early 2000’s, when most of that went to digital. I too really enjoy all of these engine vid series &, anything else you’ve put together/uploaded for us! One of my top 5 sub YT channels! 👍🏻👍🏻

Thank you Adam This was interesting. It answered my questions about the Oldsmobile 350 5.7 liter diesel V8. I had often wondered why didn't they consult with someone with expertise and develop over time. I understand now. I know Ford got BMW diesel in Lincoln for a minute. I guess no one has learned anything because Volkswagen and all those European carmakers got in trouble. and so many people paid for that mistake. Thank you. I like that name of that engine "Toroflow". It should have bused used on the Toronado in some capacity for a feature or something. Thank you again. I guess I realized no matter what Oldsmobile did it was not going to get that diesel right.

I had a really strange motor in a GMC truck. It started life as a V8 Toroflow. Somewhere along th line, th heads and intake manifold was swapped out with gas motor parts. I remember that it used th same starter as a John Deere tractor. I sure was glad when that thing finally blew up.

I remeber GM teuck and bus in Pontiac. The place was huge. Gm leaving Pontiac really hurt that place.

thanks for the video man :) well done

I remember when gas was .58 cents a gallon ! We just burned that up like it was nothing ! My buds 73 buick 454 got 20 mpg and we would cruise all night long with gas to spare !

Putting the "General" in "General Motors".....😎

7:52 that piston / head combustion interface is typical of almost all CI engines. Some Dieselized SI would be an exception. I think the Olds CI had SI type cylinder heads.

I was a mechanic in the 70s, it was a mechanics, in joking recommendation that the car owner should purchase and carry a spare crankshaft because the original would usually break. The breaking part was no joke, because they did on several occasions.

Not sure what problems the 6.2l had which you referred to. I knew quite a few that had long lives.

Alright! Thanks for another interesting video. Interestingly enough I personally drove a 1968, GMC 6500 straight truck with a 21’ refer box, with a 351 Toro Flow Diesel engine. With a 5 speed low hole 1st, wide ratio w/OD, and a 2 speed rear. We used in a family trucking company. I was bottom man in seniority so I was stuck with “Shaker” as it was affectionately called. But it ran very well, used little oil to leaks not burned, plus it true that used half the fuel the same truck with a 305 V6 Gas used, plus was quicker if you knew how to split the gears, plus higher top speed at 74 mph, as apposed to 72, at the same rpm’s. Funny thing is Shaker looks just like the blue one in the video only with a big white refer box on the back. I personally put well over 200,000 miles over the 8 years I drove it. Then after the union forced us out of business, my Dad sold the truck to a cousin, that wanted that engine for an old tired GMC 2500 step side pickup that had a 305 V6! That had 180,000 miles and was tired. He was restoring it and figured might as well sell that gas engine and trans, then buy the Toro Flow truck off my Dad, rebuilt the TF and use in the pickup, being the very rare diesel powered all 1966 GMC truck around. He rebuilt it, added two air cleaners, one on each manifold and huge dual exhaust out the sides. That pickup was used to haul out dirt bikes and tow a trailer with 10 others for a group of riders following in their other vehicles. Before? With the tired V6 gas, three speed? It was a chore, waiting for it to keep up. But after that? With the rebuilt TF? with 5 speed? He had to add disk brakes in front! Because of the speeds it would easily reach so quickly, especially when towing the trailer! Plus got more than twice the mileage, like 26 highway, 18 towing! With a wonderful sound! Everyone wanted that truck.

I bet Detroit Diesel would have advised to install a water seperator :)

That diesel at the end sounded very nice Adam. 👌 Unintentionally much needed for me. Lol

I saw one of these in a marine application. I don't think it was kinder to it that the truck application. The boat was about as streamlined as a brick. Normal speed was about 7kts wide open was about 7.1kts.

I did not know that General Motors built the Detroit motors. Thank you Adam!

Awesome!!!

The non-cross flow head design looks like that of the typical domestic inline four or six cylinder engines of the time.

Saw many of these in old dump trucks used to haul fish guts on the warf

Woah! I never noticed the valve covers being held on by screws on the V6 Jimmys, as seen in the opening photo!

I don't understand that GMC was using balance shafts in their 60 degree V6 & V8 engines. Why didn't Buick use a balance shaft since they worked in GMC engines in their 3.8L (231ci) V6?

They did not follow the normal formula for diesel engines in that the stroke is usually longer than the bore diameter because in truck type operation you are looking for torque more than top end power. Diesel internal components were generally much heavier so you wanted to keep the RPM down anyway. they are interesting engines that I have never come across. I have repowered 4x4 vehicles with the 350 GM diesel and found it not that good compared to other brands. I wonder if there are many used engines from this GMC series in breaker yards and the like? The pistons with the combustion chamber in them are called Herron chamber pistons and you find them in most diesels as it is easier to machine a piston than it is a head and diesel pistons usually have a thick crown on them because of the combustion pressures and to dissipate heat.

Nice!

Cool engine, never seen a non-crossflow V6 or V8 before

I had a 478M V6 gas in my 4900 Alison automatic GMC boom truck . Excellent motors. Truck was faster than diesel but burned alot of fuel . 8.1 pincher 366,427 replaced these later .

GMC 302 inline sixes are an older motor than most Adam has covered, but the 302 is kind of like an earlier version of the Ford 300 inline six. In the 50s aftermarket parts made the GMC 302 (1952 to 1960) a hot rodders favorite. The GMC 302 shares the bore with the Ford 300(4" x 4"), the stroke of the Ford is 2 thousands less than the GMC. The aftermarket once produced alloy 12-port heads for the 302 GMC, the newer Ford 300 always had 12 ports. It almost seems as if Ford engineers were an admirer of the hot rod history of the GMC 302 and reproduced their own version just as GMC adopted a new truck v6. The GMC 302 was so popular that more than one 12-port aftermarket alloy head was manufactured, now highly prized by collectors. The 302 is a great nostalgia motor, and when modified is still pretty powerful.

I've heard of all of them but I'm really into cars great episode tho

I would bet that this diesel version was the smokey and slow engine I had in my school bus in the early 70s! It had the same front end as that semi-tractor you pictured. On the other hand, these GMC engines were much tougher to begin with then the Olds Rocket 350, and would have been an easier conversion to diesel... One question, why would a 60-degree V6 need a balance shaft?

If you needed a ~150 hp diesel in 1964, I can't imagine picking one of these instead of a 4-71 Detroit - offered by the same corporation! Unless the price difference was extremely steep...

that's nice.

My neighbour , Gig, an old trucker, said the twin 6 would pass anything but a gas station...

I had a 1975 Monte and absolutely loved it other than it's lack luster performance. It was such a great car that I fully restored it in 1996 (rust had taken over) then finally sold it in 2002. I miss it a lot. 1978 to 1981 were meh, but 82 till it ended was nice. Then, my wife had the 2002 Monte Carlo SS Highsport. We had that for 10 years. Another beautiful car in Competition Yellow.

Looks like the OG 348 design.

My brother had an old red gmc 4x4 351 diesel on 40s back in the day! That thing was slow as fuck with the granny gears but man it would drag another truck through the mud hole like nobody’s business

I had a 63' GMC pickup w a V6. Loved that old truck

Cool 🤔👍🏾

New Idea put both the gas and diesel versions in their Uniharvester on the agricultural side. The gas engines were known to catch fire because caff would build up.

Being a ford guy hearing "351 V6" is definitely odd

The 6.2 was a great engine. It really did go a long time when taken care of. Even the olds 5.7 could be solid when not in a vehicle. They made excellent irrigation power units. The 8.2 Detroit was an absolute turd. It’s a shame the olds stuff wasn’t better because we would have a different American car industry today had they been able to prove themselves. Us Americans seem to have an obsession power output stats but all my 6.2/6.5 equipped trucks have had a good seat of the pants feel to them. Last forever when used for their purpose. Very low cost of ownership compared to other diesels.

Toro flow may have only had 150-190 hp but they had 600 ft lb of torque

I actually have the plaid valve covers for my 305c 😂. The thirfty V6 they called it

That fired up easier then my new dd5

Low HP numbers but big torque numbers.

Neat to see they were using direct injection back then. That would've made them noisier, but more fuel efficient than the IDI designs used in the 350, etc diesel engines. Direct injection also puts less load on the cooling system. The 2 stroke Detroits are also direct injection.

Now if they would of put a turbo or blower on it then it would of been a great engine

Those Toro flos would probably be good intercooled and turbo and more fuel

G m c gas v six lots of low end torque small stromberg 2 bbl carb spark plug location between intake manifold and valve cover and a sound that was like no other could hear it coming a block away!!

9:12 I always wonder why the fans of some of these old engines are not symmetrical?

Somebody who knows more than I can chime in, from what I read, they were also used in general motors coaches, the fishbowl.

Following Steve Mags KZfaq channel I know alot (or at least all I need to know) about Toroflows!

I always find this stuff so fascinating, but my question is always why did they produce so many odd low production, unknown engines? What was the point back then? Many mfg did this.

Al I hear is the Monty Python album in my head from childhood saying: "Wankel Rotary Engine"

Not sure I agree about the Detroit division not being able to help the design issue with the olds diesels. They seamed to figure out how to handle the increased compression and the injectors.

Isn't it a testament to GMC engineering that they could build a successful diesel off an original gas design with minor modifications?

..omfg i need one!... the motor around 1:05

Is this a rerun?

I do know that Pontiac nearly offered a hemi V-8 because Ed Cole wanted to drop the 6 pack from Pontiac because of environmental issues.

Wonder how they'd respond to a turbo?

I know a short run doesn't hurt them but it still bothers me when I see an engine started and running with no coolant flowing through it. So easy to drop a garden hose in there and keep it cool.

64' Wildcat 401 2dr great interior/bench 80,000 mi all chrome good little rust needs body wrk runs drives great 10k obo

I know about these because of steve mags

I suspect toro-flow refers to the supposed torroidal flow pattern of the charge air due donut shaped piston crown?....

1st spring is coming view!

Anybody want to see what one of those gassers would do with a pair of turbos? Kind of curious what the diesels would do with some turbos? It's difficult to get any real hp out of an NA diesel. I had a 7.3 IDI Ford and it was like 180-185hp so not really that much better than what these were doing 20+ years earlier.

The ecoboost v6 petrol stills runs divets in the pistons for the direct injection.....

Sounds like an old Mercedes diesel in their cars back in the 80's. Other than straight exhaust.

Thunderbolt Grease Slapper Is what it sounded like

Very loud hardly does a Detroit justice. So loud it will tear a hole in spacetime gets a little closer.

I’m guessing it’s called the toro flow because it has horns like a bull