GM’s Worst Engines: Why The 1981 V-8-6-4 368ci Engine Was a Failure

Learn more about Cadillac's one year only 1981 V-8-6-4!

[@johnh2514]

My uncle worked for a large Cadillac dealership in the early 80s. He told me for a time the service department each week did dozens of disabling jobs of the system. Once deactivated, the 368 was a solid and reliable engine.

[@scotttwombly6528]

Ours ran fantastic for years once it was deactivated, I really like that 1981 El Dorado

[@craigroosa9321]

Mine was also deactivated and ran beautifully ! Had the Seville Elegant .

[@93sundance]

I worked with an old Cadillac tech who told me once they were disabled it was a nice running engine.

[@MarinCipollina]

@@93sundance Yeah, but it was a still underpowered dog of an engine. I say that as a former 1980 Coupe de Ville owner

[@MarkWG]

@@MarinCipollina I owned a 1980 Seville Elegante' and a 1981 Eldorado, each with the 368 engine. It had loads of torque to pull that weight and 160hp. No problems cruising at 80 mph all day on the highway. 154,000 miles on the Seville, BTW.

[@zeon5323]

I had my Arco station back at this time and we had a number of customers with these engines. These people were not concerned about MPG, they wanted smooth. After many trips to the dealer with no improvement they came to see me. Disconnecting the brown wire at the transmission would keep it in V8. My customers were happy.

[@t.l.robinson2162]

You can put it in v-8 mode through the mileage display on the dash.

[@kaleb8518]

​@@t.l.robinson2162if it even wanted to work in the first place 😂🤣🤣

[@vinnyp3351]

I remember when I was a kid my aunt and uncle bought a brand new 1981 Cadillac Coupe Deville with that engine. After they picked it up at the dealer they stopped by our house to show us the car. And the car started giving problems in our driveway. They had to get it towed out of our driveway.

[@randyfitz8310]

The selling dealer should have given it a good break-in test drive prior to delivery.

[@BillofRights1951]

That happened a LOT. We knew the owner of Symes Cadillac in Pasadena Ca...they had customers who didn't make it home from the dealer picking their car up as new. The dealers didn't know how to fix them. The early 80's were a disaster for American cars. We bought our first Honda (a new 1983 Accord 4-Door ) in the fall of 1982...got us thru the next 8 years without a problem. Started buying American again in 1985 with a new Jeep Cherokee Chief....loved that car.

[@Edward-tp5nc]

It was an excellent engine… It was simply the computer that you unhooked and then it ran just fine.

[@michaelpfaff6009]

We had a 1981 Fleetwood Brougham; grey exterior and grey, button-tufted velour interior. The most beautiful car and the most comfortable car ever. We had a toggle switch installed that was mounted under the dash. We kept it in V8 mode while in-town use and flipped the switch to the V8-6-4 mode on the freeway. Ran like a top for 10 years. Absolutely no issues with that engine. The car was a delight. Too bad it wasn't just a V8-4 engine.

[@ericknoblauch9195]

A friend of mine bought one of these in a junk yard in the early 1980's for $1,000.00. He had a toggle switch installed too. He also said if you kept the engine oil changed and kept the filters changed the engine ran ok. He ended up with a practically brand new Cadillac at the time for practically nothing. That Cadillac ran for many years. He did say the only difference was his Cadillac had a salvage title because he bought it from a junk yard. He also said it ran ok when it was in the 864 mode. He stole that Cadillac, and had it for almost 20 years. People were jealous because he got a Cadillac for practically nothing.

[@brianhardy5926]

I bought a 1981 Fleetwood Brougham d'Elegance coupe with the V8-6-4. It had a grey exterior with a blue button tufted velour interior and a matching blue vinyl roof. The blue vinyl was colored at the dealer to change it from the factory grey. With that blue velour interior, I called it my "Pimpmobile". I had that car for 10 years until it got stolen from the parking lot of my wife's job. Its parts were stolen and it was vandalized and ditched by the side of the road. It felt like rape. I loved that car. The only time I had a problem with the engine was very early after having purchased it. After I took it to the dealer to have it fixed, I never had another problem.

[@t.l.robinson2162]

I had a '81 Sedan DeVille with a 8-6-4 368. I locked it into 8 cylinder mode and drove it 340,000 miles trouble free. It required just routine maintenance.

[@craigroosa9321]

Had the Seville ,,same engine and did the same ! No problems . Great car ,loved it.

[@GoonSquadLifeMember]

Those 368/6.0L weren't going to win races, but they were TOUGH engines overall.

[@mikemichaud5048]

Same. 187000 then developed an electrical problem and my mechanic started yelling at me to buy a new blank car! But I loved it!🙂

[@samholdsworth420]

​@@GoonSquadLifeMemberunderpowered v8s are recipes for long lasting engines😊

[@edwardpate6128]

The actor here is Don Matheson who is probably better known for his character Mark Wilson in Land of the Giants. He also guest starred in an episode of Lost in Space where he uttered the immortal line, "Crush, Kill, Destroy!

[@TheTussman]

Yep. Land of the Giant Pencils for comparative size.

[@seiph80]

So he was the IDAK guy?

[@jondoes7836]

Instant Destroyer And Killer. IDAK for short.

[@dosgos]

Great marketing pitch and (seemingly) great idea. Car makers still are struggling with cylinder deactivation, so it is not a trivial problem.

[@w.e.s.]

It's not a struggle anymore. They stay in 4 cylinder mode unless it's floored for 5 seconds straight then u get v8... even idles in 4 cylinder mode. They over done them

[@samholdsworth420]

​​@@w.e.s.correct but those lifters eventually fail prematurely.... So there's still a problem with the system 😊

[@johncocktoasten9228]

The current displacement on demand engines GM has now still SUCK! Oil changes are absolutely critical for these engines or they blow up.

[@unpopularopinion3158]

They'll blow either way, shutting fuel does more than just not powering that cylinder. The rings are actually lubricated by fuel as well!

[@joeapplebaum3763]

I lock my ‘20 Suburban to where it won’t go past 5th gear and it stays in V8 mode. The mileage is still decent. Hopefully this will help in the long run.

[@phantom0456]

@@joeapplebaum3763Does it have a ten speed or an eight speed? Just curious.

[@joeapplebaum3763]

@@phantom0456 it’s a 6 speed.

[@phantom0456]

@@joeapplebaum3763 Oh ok, I forgot they were still putting the 6 speed in the Suburban in 2020. That’s at least a decent transmission, unlike the 8 speed.

[@bigcrowfly]

More than 40 years later the advice to anyone buying any vehicle, new or used, is to avoid Cylinder Deactivation (or whatever name given it to hide its presence). Whether it is GM, Honda, Ford, Mazda, Mopar, VW, BMW. Mercedes Benz, Hyundai, or others, ... avoid high mileage versions with CD.

[@adamtrombino106]

In general, I would agree. I may have the exception in my 05 Acura TL 3.2 with the 6 speed manual. Even at 203k, it still gets 34mpg at 70 mph with the cruise on, on the highway with no trouble. AND that being said, I have always changed the oil at 3000 miles, so that might be why it still works. Car is getting pretty rusty now, so its days are numbered....

[@MostlyBuicks]

The time, money and energy to get a few more MPGs was counterproductive in so many instances.

[@bcubed72]

The old adage: "If you want economy, buddy, you gotta pay for it!"

[@mark_osborne]

I worked on dozens of these cars back in the day and even owned an '81 Eldorado that I drove for years. Wonderful vehicle. Yes, some computers suffered from RF interference causing the 8-6-4 feature to act strange at times. It was a isolation problem. Nothing to do with the functioning of the rocker arms or fuel injector, which BTW simply cut it's pulse-width in half (in 6 cyl) and shut off entirely (zero pulse width) in 4 cylinder. It worked excellent. As a test, I un-pluged the oil pressure (governor pressure) switch on top of the transmission ( you could easily reach it) causing it to remain in 8 cylinders all the time. The fuel economy at a steady 70 mph went from 16 mpg in 8 cylinder, to 26 mpg in 4 cylinder. It was wildly effective. It is my personal opinion these cars got a very unfair rap and were truly ahead of their time

[@davidpowell3347]

Should have had Manual control of the number of cylinders active. Except when cold (warmup mode cycle) when all cylinders should have been active. Actually all of the cars with this scheme today should have manual control over the cylinders active. Still giving problems and causing premature engine wear and cylinder scuffing to this very day. Should also rotate turns between active/inactivated to all the cylinders in sequence that the feature is used.

[@HighSierra1500]

It was an innovative idea for the 1980s. You only fail if you don't try and Cadillac tried.

[@cardinaloflannagancr8929]

I agree I think if it didn't get such a bad rep so quick they could have worked out the kinks in fairly short order. Not perfect but to where the drivability was still good most of the time. With cylinder deactivation and the gear hunting of the now up to 10 speeds after this many years it isn't that much better. Heck just having EFI fuel injection with the same 8-6-4 system wouldn't be any worse than new cars.

[@bradbergman9182]

​@@HighSierra1500yes, Cadillac tried and the customer paid for being a guinea pig. And they wonder why the Japanese took over so much of the market.

[@t.l.robinson2162]

The car was very easily locked into 8 cylinder mode through the mileage display on the dashboard.

[@DavidPysnik]

Basically CAFE helped wreck Cadillac. In just 9 years 5000+ pound cars with 8.2 liter engines became 3400 pound cars with 4.1 liter engines and lost as much as 38 inches in length and 8 inches in width to boot. Such a radical change took Cadillac from what it did best, making enormous luxobarges with reliable gas-guzzling engines, to having to downsize drastically while trying to maintain some semblance of power and prestige. The technology just wasn't there fast enough, and a whole bunch of bad engines along with tiny, cookie-cutter cars destroyed Cadillac's reputation. The more reliable 4.5, 4.9, and Chevy-powered Fleetwoods of the time were helping to dig them out of the hole, but it was too little too late, especially once the Northstar head gasket debacle occurred.

[@georgeburns7251]

GM didn’t need CAFE help to ruin cars. Do you wonder why they went bankrupt?

[@adamtrombino106]

CAFE and emissions stds of the late 70s early 80s hurt everybody. GM was shuffling between various Olds 307s, Buick 231s and 252s, Chevy 229s and 305s, Pontiac's 151, 267, and 301s, and Caddy's 368, then the whole HT4100 debacle. Don't forget the diesels. Ford was stuck with the smogged out 200, 300, 302s and a few 351s left. IMO, Chrysler was in the worst shape. For 79 you had a 225, 318, and in select cars until 81, the 360. From 81 until 89, if you wanted a RWD Mopar car, you were stuck with either a 90hp 225, ( until the 1985 model yr) or a 130 to 140hp 318 with a terrible rear end ratio. Adam did point out that in most cases, you could get better highway mileage of maybe 2 to 4 mpg, but in the real world, the loss of useable power hurt the cars so badly that 1 really did have to get used to driving much more slowly.

[@MrSloika]

The 4.1, 4.6 and diesel were all steaming piles but the engine used for V8-6-4 was based on the L61 which was a decent mill. The problem with this car was the engine management system which was not up to the task, the basic engine was fine.

[@johneckert1365]

C'mon, the later years of the diesel weren't so bad.....

[@adamtrombino106]

The 4.1 Buick should've never gone into full sized GMs. Rated at 125-135hp depending on emissions packages with a 4bbl carb, they were miserably slow and in the real world, got terrible mileage because you had to have your foot deep in it to keep it moving with 4 aboard. Maybe in a controlled experiment at 55 mph with the cruise set, it looked good on paper, but in the real world....

[@5litreho]

The 368 Cadillac V8 is in the same engine family as the ever so reliable 472 that was inroduced for the 1968 model year. The 368 is a good engine, but, the additional electronics with DOD gave it a bad rap. Cadillac should have kept the Olds Rocket 350 as their primary. That engine had MPFI, and was very reliable !

[@johneckert1365]

100% agree. Even the Olds 307 that they used through 1990 was a good carburated engine, but the Olds 350 probably would've gotten better fuel mileage, especially with EFI.

[@mbp2112]

I owned a '80 CdV with the carbureted 368, it was the sweetest running carbureted engine I ever had. I dailied it in and out of Boston for a while and it never missed a beat, never overheated. I thought the torque was adequate. Shame that Caddy tossed the baby out with the bath water, and rushed out the hideous Hook & Tow 4100, which maybe did more to damage their reputation than 8-6-4.

[@craigroosa9321]

I owned a 1981 Seville with that engine with it disabled . Not fast but smooth and trouble free , Two tone as you have pictured in video , silver and burgundy . Very elegant car. You either loved the look or hated it ,,I loved it .

[@myronfrobisher]

compared to the HT-4100 & the North Star the 864 was a bloody jewel !!! If I could find a 1981 Eldorado with the 864 I would snap it up.

[@HighSierra1500]

Back in 2011 I found a 1981 Cadillac Fleetwood with the 368 cubic inch V8 engine. I didn't buy it though. The seller was too shady. When he told me I had to pay cash because bank drafts can bounce, I ran.

[@johneckert1365]

Me too! Those 79-85 Eldos were BEAUTIFUL cars. Riviera/Toronado wasn't bad either, but the dumb looking Seville always gags me.

[@myronfrobisher]

@@johneckert1365 Gag is a perfect descriptor - after producing a complete winner in the 76 - 79 Seville to replace it with a copy of an out dated Daimler was suicidal - it was the beginning of the end for Cadillac - the damn things drove and road like a bucket.

[@joelyons3713]

I had an 81 Seville, at some point before I bought it, it had been converted to an Olds 307.

[@richbanducci7756]

In 1981, my dad bought a beautiful triple black Eldorado with the 8-6-4. After owning the car for several years, the 8-6-4 turned out to be one of the only things on the car that was NOT problematic. His Eldo was built without one of the crank bearings and it took the dealer nearly 3 months to find it!

[@johneckert1365]

WOW

[@B3burner]

I remember those being advertised when I was a teenager. Seemed like a great idea in theory, and I can’t fault them for trying it. However, the execution was just amiss. What a shame for a car brand I’ve always rooted for, since I was 7 years old.

[@wumpusthehunted2628]

I strongly suspect it was conceived as.a v12 to i6 converting engine, but management wouldn't spring for the v12 and the engineers were stuck with a recipe for failure Note: I have no idea if it would work, just that the i6 would never make driving down the highway feel un-caddylike, and it would allow cutting the displacement in half.

[@angryshoebox]

The Olds diesel, the V-8-6-4, the HT4100, and don't forget the Cimarron, LOL. Yes, Cadillac was really stumbling in the early '80s.

[@zlinedavid]

The Cimarron wasn’t necessarily a bad car, it just wasn’t a Cadillac. It was a Cavalier with leather. 😂

[@hurricane2649]

GM has always rushed things to market without proper R&D. They have been doing this for decades and still are to this very day.

[@mbp2112]

Somewhere a 3.6 just slipped a tooth on the timing chain. 😢

[@dustin_4501]

It begun with the Vega.

[@hurricane2649]

@@dustin_4501 Yes, it did. GOOD POINT. I forgot all about that.

[@DinsdalePiranha67]

I've said for years that their slogan should be "General Motors: Great ideas, poorly executed."

[@chrisxa1222]

If that was 'always' the case tell me an example before the vega

[@palmermccall7309]

My '77 Sedan DeVille with 425 was adequate, but seemed heavy and fairly slow compared to my '80 Sedan with 368. The '80 was light and responsive, and had terrific balance and handling. Later I had an '84 Fleetwood with HT4100 that was predictably a slug, and then an '86 Fleetwood with the Olds 307 was only mediocre. Dad had an '83 Seville with HT4100, not superb, but better than the RWD C-body. Friends of the parents bought an '81 Coupe new with the V8-6-4, liked it and had no problems until it was traded about 1986. My biggest lament about the V8-6-4 is that it basically meant the end for the fantastic 368. My 1980 Sedan now seems like it was a unicorn, and I seem to remember topping 20 mpg on highway trips!

[@adamtrombino106]

The Olds 307 was ok in traffic and city driving. Getting to highway speeds was a long chore, and passing? Not today. However, it was at least reliable. You can't say that about a HT4100. IMO, when the last batch of old school Fleetwoods were produced with the Chevy 305 and 350 TBI engines, you finally got some semblance of full sized American luxury with a bit of power to boot. And they got surprising highway mileage as well. GM finally got it right for a couple yrs, then blew it all up with the Northstar...Nowdays, again IMO, Caddys are a complete joke.

[@MostlyBuicks]

The Cadillac 4.9 is not too bad. The Northstar COULD have been great with hardened steel inserts in the block to anchor the headbolts and better gaskets in the skirt and oil pan. So, I declare the carbureted 425 was the last GREAT Cadillac V8.

[@moejr1974]

The Caddy 4.9 was the 4100 finally fixed

[@johneckert1365]

​@@moejr1974Even the 4.5 was decent.

[@adamtrombino106]

@@johneckert1365 The 4.5 and 4.9s continued to suffer oils leaks that just couldn't be fixed. That turned a lot of older repeat Caddy buyers off. If you have to throw a piece of cardboard down under your $50-60k Caddy to keep your garage floor clean, or park the thing in the street to spare your relatives' driveway, why buy another?

[@johneckert1365]

@@adamtrombino106 good point

[@chadakoin1]

When these were introduced I totally understood the concept. The ancient Olds 88 I was driving at the time practiced it's own form of cylinder deactivation, particularly in wet weather.

[@anthonyjackson280]

". . .if you can believe 429 CID was too small . . ." The Beast of Turin enters the chat - "EACH of my 4 cylinders is 427 CID" (1910 FIAT racing car. Has 4 cylinder 28L engine - still exists and is driveable)

[@loveisall5520]

One of my cousins bought a 1981 sedan Deville with the six cylinder option, white with a blue interior. I rode in it many times, and it was a most pleasant and reliable car for him. I guess it wasn’t overly fast, but certainly it would carry, several people in comfort and I never noticed it being overly slow.

[@claytoncherry3192]

I've spent a lot of time under the hood of my 1981 Eldorado working on one of these. It really fought me coming back to life. I finally got it reliable enough to take Certain Failure off the keychain and take it on a road trip to Vegas and the Hoover Dam. They can be good cars but they need a lot of love from an experienced mechanic.

[@corvetcoyote443]

It wasn't the engine,it was the fuel injection that failed,the 1980 had the same engine and it was a great car but GM thought that the HT 4100 would be the way to go, but I think that engine was crap.

[@2packs4sure]

We had some family friends who were big GM people,, we were Ford people,, and in the early 80's his wife had 2 bad Cadillacs in a row and he had 2 bad Corvettes in a row so the next thing we know she's got a Town Car and he's got an 85' Ford Bronco with the 5.8 HO 4 barrel and from then on he was a Ford guy,, and for the rest of his life...

[@1940limited]

The 80s were definitely not great years for GM.

[@ChristopherSay-qh4nc]

I’ve never met a Ford family that switched to GM. Never.

[@2packs4sure]

@@ChristopherSay-qh4nc Lol,,, I'm sure it's happened but the GM to Ford switch was happening A LOT in the 80's and 90's and with good reason.. I remember new truck shopping in 85' and it was absolutely going to be a Ford,, and it WAS,,, but I decided to test them all and MAN,,,,,,, there was no comparison !! I remember being totally shocked driving the Dodge especially,, it was weak,, sloppy steering,,, mushy brakes.. The Chevy was better but was a no go just on cab space alone,, felt like my nose was touching the windshield..

[@saltyreesescup3104]

My Cousin Bought One For $500 In 2000. Had 130,000mi. Ran Perfect. 8 6 4 Still Worked As Intended.

[@1940limited]

Definitely a rarity.

[@saltyreesescup3104]

@1940limited Ya, Thats What I Told Him.🤠

[@Sevenfeet0]

One of my grandmothers had the '76 Sedan DeVille and the other had a '77 Coupe DeVille. I briefly had the '76 car after she passed but it needed too much work and I couldn't keep it. My first Cadillac I drove as my own car was a '80 Coupe DeVille which I had in college in the mid 1980s. The '80 looked so much better in terms of proportions versus the '77-'79 cars. Cadillac kept the look of the '80 car all the way until it was discontinued in 1992! But Adam is right, the progression from the Olds Diesel, to the V8-6-4 and finally the HT4100, all within a period of five years was the most disastrous series of launches for just about any auto maker, especially for a prestigious brand like Cadillac that had in its past the Dewars Trophy, the V8, V12 and V16s of the 1930s, the OHV engine in 1949 and a steady progression of more and more powerful engines all the way up tp the 8.2L V8 in the '70 Eldorado. The 6.0L "Big Block" in my '80 DeVille wasn't fast but it didn't give me (or my brother who drove it into the '90s) any real problems. I remember reading something in a car magazine in those days that the V8-6-4 was developed in a short 10 months from concept to production because GM was so desperate to improve its CAFE numbers. It was a great idea that was more than two decades ahead of its time in terms of execution. It was so bad that the HT4100 that wasn't supposed to be introduced until the downsized full sized Cadillacs of 1985 got pushed ahead to production three years ahead of schedule. The result again was predictable. It was a poorly executed product that needed more time in development to get right. Despite the early teething pains of the Northstar V8 in 1993, it wasn't nearly as bad as the Olds Diesel/B8-6-4/HT4100 debacle of 1978-1982. You knew that GM was hedging its bets on the V8-6-4 in a major way when the Buick 4.1L V6 was offered alongside the V8-6-4 in 1981 and again as an option in 1982 versus the HT4100. Why on earth would a typical Cadillac buyer choose the V6 when the whole point of the V8-6-4 was that it could get V6 economy while still giving you 8 cylinders? Why is this option here at all....unless the V8-6-4 truly sucked and some folks at GM probably knew it. And of course the Olds Diesel V8 was on offer and literally could not get out of its own way. In addition to making their CAFE numbers better, I think Cadillac of that time was trying to woo Mercedes buyers who choosing their slow but generally better Diesel engines.

[@johneckert1365]

Once most of thr bugs were worked out of the Olds 5.7 diesel they really weren't so bad. With an aftermarket water/fuel separator and regular maintenance they were good for 200K+ miles.

[@Sevenfeet0]

@@johneckert1365 "with an aftermarket water/fuel separator". And here is the crux of what I was saying. Products introduced way too soon without either refinement or in this case, necessary stuff and destined to fail. And it still couldn't get out of its own way on an Interstate ramp.

[@johneckert1365]

@Sevenfeet0 I agree with you. The diesel ABSOLUTELY needed more R&D before it's release. Just like the TH700R4. Just like the Vega. At the end of it's run, the Olds diesel was alright. The TH200R4 behind the later models allowed for a better rear-end ratio, which made it much better suited for freeway on-ramps.

[@BugsBunnysBrother]

I had a limousine service that used the Fleetwood 75 as our corporate transportation vehicle. The cars were great as they could move 5 people comfortably on velour seats (in the rear) and leather in the front. The divider was manual, the rear passengers could control the a/c as well as the radio and there were 2 seats that you could open (un- fold) and you then had seating for 5 in the rear. This was called the formal limousine. The engine was an 8-6-4, and it was just the worst for gas mileage and dependability. In our fleet we also had a Sedan De’Ville with a 4100 engine in it and everyone preferred the 4100 to the 8-6-4. I was able to have the 8-6-4 disconnected to just run as an 8. I was able to buy 3 1984 ‘s with 3000 miles or less for 25k or less from an investment banking firm. Running them just as an 8 cyl. was great. No great mileage but lots of comfort and lots of room for luggage and people. It was also great to use around Wall Street . This was before the stretch limo became popular. I ended up selling them all and making a profit from them. Caddy came out with small limo that were awful and soon we converted to all Lincoln town cars. They were great. The best thing about the caddy was driving in lower Manhattan. You could make it around the tight curves which you could not do with a stretch limo. Also the FDR drive had a weight limit of 6000 lbs at 96th street going south. These cars were about the worst caddy ever offered.

[@MarkWG]

The V8-6-4, 368cid, was still a good, sound engine with torque and adequate power. All you had to do was reach under the hood and yank one plug. Problem solved. You got a true, Cadillac big block V8 that ran on all 8 cylinders. So, what's the fuss? I had one, unplugged the V8-6-4, done. Simple.

[@madmike2624]

Oh, The early eighties and the overreach with electronics by almost all manufactures!!!

[@HighSierra1500]

My dad and I were talking about the V8-6-4 and the HT4100 grenade. He joked that Cadillac went from "The Standard Of The World" to "The Terror Of The World"!

[@dustin_4501]

Props to your dad, that was funny.

[@JohnGruber-di3cw]

Cadillacs always seemed to be way overpriced!!! From 1970 on up they were no better & even worse than big Buicks or Olds!!! The 50's & 60's were Cadillac's best decades!!! Cadillac should have been eliminated instead of Pontiac & Oldsmobile because they made more affordable decent cars!!!

[@MarkJones-zg6si]

😂😂😂

[@davebittner822]

My father had one of these, and it was nothing but trouble.

[@dmandman9]

At least the base engine was solid. So if the engine was made to stay in v8 mode, it was solid

[@geyser3445]

When I heard Mazda had 2 cylinder deactivtaion, it remiinded me of this engine.

[@komradkolonel]

Even today I won't want an engine with cylinder deactivation. The fundamental problems are still there. I had a neighbor who was a mechanic and he worked on these. Or I should say he replaced these.

[@Paul1958R]

Everything Ive seen from MANY good automotive youtube channels shows that the current generation of GM AFM/DOD engines have horrible reliability and longevity. And just like the V864 of old the only real fix - after replacing crapped out lifters - is to disable the feature. Some things never change at GM.

[@user-zx8de8op9l]

Well done explaining this engine's failures. My uncle hated his 1985 with the 4.1 engine.

[@billycook2222]

I had a 1981 Eldorado Hess & Eisenhardt custom convertible with V864. I worked flawlessly and most time was spent in 8 and 4 cylinder modes. The 6 cylinder mode was more for transition. I guess I got a fluke since my Eldorado always ran well. Great video as usual Adam.

[@The_R-n-I_Guy]

Still better than the crossover garbage people drive today

[@HighSierra1500]

True. Back then you could disable the system buy unplugging it. Today, with one system tied into two other systems, you have to grin and bear it until the vehicle is paid off. Then you can dispose of the whole car all together.

[@maplemanz]

I agree.

[@maplemanz]

I hate crossovers

[@dozerm.4108]

It bugs the hell out of me when sources degrade this engine. In all honesty it was last Cadillac engine that was any good, being an all iron block and heads, and its roots were from the reliable 472, 500 and 425 engines prior. Just delete the cylinder deactivation and you have the same 368 from 1980. Cadillac was forced to do this to meet cafe standards, when they saw that it was a failed system, option B was even worse in 1982 by resorting to the HT 4100.

[@HighSierra1500]

One of my teachers in college referred to the 4.1L V6 as The Dreaded HT4100 Grenade. If coolant got between the aluminum block and the cast iron sleeve, it would make steam and blow a hole in the side of the engine.

[@kevineich5029]

@@HighSierra1500 The 4.1 L V8 was the engine that had issues. There was a warning label indicating the GM supplemental cooling system sealer MUST be used in these engines or severe engine damage may occur. Many owners did not heed this warning and treated the engine like any other engine and when it had problems, the engine was always blamed. We had two of the HT-4100 engine Cadillacs in our family back in the day - both went over 200,000 miles with no major engine work.

[@zlinedavid]

@@kevineich5029And by the time they introduced the Northstar, they had all the kinks worked out. The 4.9L is actually a pretty solid engine.

[@kevineich5029]

@@zlinedavid Also, by the time the 4.5 engine was out for the 1988 model year it was a very reliable engine. Improvements in gasketing and sealing technology continued when the 4.5 was stroked to produce the 4.9 engine.

[@zlinedavid]

@@kevineich5029 And the addition of port fuel injection helped a lot also.

[@rumplestilskin5776]

My uncle had one of them in his Fleetwood, what a hunk of junk.

[@garyruark9506]

Nice. There is a beautiful 1981 Eldorado for sale near me. It has the V8-6-4. Been for sale for months.

[@kevingavigan7883]

A common "fix" for this engine was that many people who bought it would disconnect the wiring, turning the V8-6-4 into a regular V8 engine. That's what I've heard anyway, not sure how true that really is. After all, one can't believe everything they hear.

[@MostlyBuicks]

People who do not change their oil on a regular basis, get what they deserve. Same goes for transmission fluid and filter (not talking about flushing).

[@jamesengland7461]

There is equal blame to be laid on manufacturers of modern cars with their false claims of very long oil change intervals. The average person doesn't know who to trust.

[@toddgiambruno]

Thank you Adam for this video! In the mid 90s i lived next to a fella with an 81 Coupe Deville with the 8-6-4. He loved that car and took great care of it. Oddly enough; he never had any trouble with his. I think he got very lucky!! Thank you again for your videos!!

[@adamtrombino106]

My uncle had 1. The 8/6/4 system kept giving him trouble. As he put it, it seemed to 'hunt' between power modes. The dealer simply told him to use the in dash button feature to turn the system off each time he started the car. No issues after that, as it was in V8 mode all the time and he claimed it actually got better mileage with the system turned off!. He traded it in for a 89 sedan DeVille, his 1st FWD car. What I will say is if you look at the valvetrain set up in an untouched 8/6/4, it was incredibly complex. Given how bad Delco electronics were in this era, I can't believe it even worked at all!

[@rickwitt5735]

Adam, I'm always impressed by how much detail you go into. This is a video that wears many hats, but the topic is spot on. I always wondered if this engine could be successful with better electronics; however, I didn't realize that their idea of fuel injection was basically a carburetor. There's essentially nothing you can do...

[@RareClassicCars]

Nope. Not with throttle body injection

[@dustin_4501]

The American car industry never was the same, once the government put their hands on it.

[@mikevale3620]

Or vehicle manufacturers can keep polluting our air, unrestricted all in the name of economics.

[@dmandman9]

Back then we were crying about 50 cent/gallon gas. Can you imagine if regular cars still got 14-16 mpg on the highway with fuel at today’s prices which hover between $3-$5 / gallon?

[@iluvcamaros1912]

@@mikevale3620 I get so tired of old dudes whining about the government. All they did was force Detroit to do what they already should have been doing. If you behave like a sane adult the government won't have to "tell" you to do anything -- you'll already be doing it.

[@nickc9224]

@@iluvcamaros1912 I get tired of people who are young and stupid and don't know or care about the politics and what was behind the gov interference.fools like you can never see the truth because you have been propogandized to believe gov talking points like a good little bolshevik. Get an education not the lies you learned in public school!

[@dustin_4501]

@@mikevale3620 I'm not saving they should keep polluting, but the government didn't help push them into this way, without giving them time to developt better cars and work out problems.

[@MrPoppyDuck]

It is tough to make a variable displacement engine that lasts. Have a friend who had an Oddessy with the V6 which shut off two cylinders in eco mode. He got rid of that van with only 60k miles due to it turning into an oil burner. Plugs kept fowling out.

[@ponchoman49]

A sound robust engine married to a technology that was introduced years before it was ready for prime time. What they should have done instead was make TBI std across the board on the 368 and installed a more robust version of the 200-4R automatic overdrive transmission which would have bumped highway mileage into the mid 20's and got them to 1984 when the new smaller FWD C-body cars were being introduced and more development time on the HT4100 V8

[@J.W.W.]

Displacement on demand is STILL a problem to this day 😂

[@thomastoler2397]

Adam, I’d like to hear you comment on something you may have mentioned before, that was that GM had been planning to reduce the size of their C-bodied cars, regardless of whether CAFE had happened. You, or whomever I heard speaking on this, said that the C-body’s dimensions were at the maximum size and that this was no longer tenable, or necessary in the market conditions of the 1970s. Thanks for all your excellent work; I check daily for your newest programming.

[@OLDS98]

Thank you Adam. I watched the video and I realized something. GM was successful with its downsizing in 1977-1979. They tried to do it again in 1985-1987 and it failed. They did it for the same reason fuel economy and government standards. I think the reason it failed the second time is they cars got too small and they no longer had divisional brand identity that stood out. GM then spent all that money correcting the downsizing in 1989-1992. That cost money, market share and time. It is interesting the 1977 new B and C bodies had the dimensions of the 1973-1977 midsized GM cars. They became the new definition of full size. Over time the engines and fuel economy got better. Cadillac however had a series of engine disasters from this engine in 1981, the HT 4100 and finally got on a good streak with the 4.5 and 4.8 liter V8 only to get back on another bad streak with the Northstar V8. The Oldsmobile diesel V8 is not winning awards and it did not help as it hindered adaptation of diesel V8's and it was under powered, and not reliable. The 1980's was not a good time for Cadillac. Thank you for talking about this engine and how this type of engine exists today.

[@ianjay5301]

We had a Seville with this engine. Going downhill, the fuel economy number would shoot up, but on the way back up, the opposite was true. I liked the bustle back styling but the engine didn't seem as nice as it should be. We had a 425 before this. Sadly, the Seville got traded in on a 4100 Fleetwood which was kind of underpowered. I had an 89 FWD Fleetwood with the 4.5 and it was much better in that configuration than the RWD Fleetwood. Today, Caddies have engines that are not unique to the models. So sad. I love the Lyriq, but again, it lacks the heart of a real Cadillac. I could have a dream car, it would be a 64 Cadillac Eldorado convertible.

[@Dac54]

And, lest we forget, to add to the misery in this time period, Cadillac also introduced a re-badged, dolled up Chevy Cavalier known as the Cimmaron. Dark days indeed for Cadillac. In the meantime, Lincoln overtook Cadillac in prestige and desirability.

[@moejr1974]

Yeah Cadillac whiffed a lot in the early 80's

[@TeeroyHammermill]

Everybody I talked to than owned these back in the day had the system unplugged. I'm not sure how the limos did it, but they were geared differently and didn't have a MPG sentinel to tell if the system was working or not. Maybe GM tricked the system on the Limos, who knows 🤷

[@danscott3880]

I was gonna Mention VICE GRIP Garage. Derek did get it running. He removed all the smog disco equipment and the throttle body and put a Holley carb on it. Ran smooth after that

[@paulwindisch1423]

That is not correct. He got a remanufactured ECM for it and ran it with the 368 cid V8-6-4.

[@MostlyBuicks]

The EPA was so concerned about the PPM, they failed to understand if you use LESS gas, you have less "M" for the "PP" to matter. It was the EPA that killed mpg in the 70s. Most American small block V8s BEFORE the EPA stepped in got 20+ mpg on the freeway. (Excepting the L79 or Boss 302, LT-1, and other HYPO engines or course).

[@ferdiepacheco923]

In 81 to best thing to do (I did with my mothers Seville); go to the dealer and disconnect that stupid 8-6-4 garbage-was only a plug on the transmission. Then, the engine went back to normal. The 82-85 HT4100 was awful and underpowered. At 90 k perfectly maintained miles my 85 Eldo dropped dead. Close to $4000 to redo the engine. In hindsight I should have replaced it with a V8 350.

[@jeffmiller3150]

Shoulda replaced in with a genuine Cadillac 8.2 litre V8, NOT some trashy Shivrotlet engine!!!

[@johneckert1365]

​@@jeffmiller3150He surely meant the Olds 350. I do agree though, a 79-85 Eldo would be awesome with a healthy 500 under the hood. Probably decent on gas with the later overdrive trans.

[@CarsandCats]

My Dad was a Cadillac man and owned a '76 Seville still in 1981. We went to look at the new Cadillacs and a salesman opened the hood on an 8-6-4 equipped vehicle. My Dad's response, "That looks like a whole lot that can go wrong." I'll never forget it as he shook his head and walked away. Way to go, Dad!

[@adamtrombino106]

My uncle was the same way. He had a '75 sedan DeVille that was starting to rust out, so he looked at an 81. When the salesman opened the hood, he was like "What is all that crap?" and the salesman tried his best to push how marvelous the system was. My uncle told me that he told the salesman to keep it. He spent the $ fixing up the old '75 and drove it another 7 yrs and it still looked good! But at 176k the engine was mighty tired, so he sold it to a private buyer. He had a Town Car for a couple yrs then bought a new Brougham with the 5.7 tbi Chevy which he loved, in 1990. That was really a good car and got passed down throughout the family long after he passed away in 1995.

[@timbullough3513]

1981 brought a brand new Ford LTD Crown Victoria 2 door to our house. What a bullet we dodged by getting a basic 302 ... even with the variable venturi and AOD being less than excellent versus the GM Diesels, V6s and oddball motors.

[@patrickburke7929]

My Dad bought the 1981 Mercury Marquis Brougham 2 Door that he absolutely Loved. Tho he had same complaints as You Describe. It was only a Few years ago I Found out that the Ford & Mercury's in 2 Door Versions where even at Brand New where Very Rare Birds. Ford built over 30.000 4 Doors as did Mercury. But in 2 Doors Ford & Mercury only Built roughly 2,700 in each Brand. Try & go online to find one just to look at & it's nearly impossible.

[@timbullough3513]

@patrickburke7929 Would that I understood the rarity at the time. It too was dad's car ... until some decade later it became mine. He loved it and I did too. Neighbor gentleman got the Olds 98 Regency Diesel that year ... oops. Family across street got a VW Rabbit Diesel in poverty spec rubber floors. That Ford was reliable, strong and beautiful inside. And it was near peak German car worship time ... I found it hard to worship with the automotive elite masses and found Detroit sedans to be my thing.

[@johneckert1365]

Those 79-up Full-size Ford 2doors were good looking cars too! It's a shame they stopped building them.

[@JohnAnderson-hr4qc]

Just another example of GM putting something out before it has been fully tested and developed. The computing power just wasn't ready yet.

[@codymoncrief8478]

My parents owned one of these in the early 2000's. My dad got it cheap and ripped the v8-6-4 out, slapped in a 400 sbc and never looked back... My mom said the car would idle itself up to 40mph. I don't know how we ever lived through my childhood.

[@RDEnduro]

It sounds great on paper

[@marcandrade4156]

This was GM handing the entire Limo/Livery business to Ford/Lincoln in the 80s 😢

[@MarinCipollina]

Thanks for this one, Adam.. I remember well watching in absolute horror as Cadillac proceeded to just completely self destruct as a brand during the early 1980s.. It was sad to watch, and it was a nadir that took decades for Cadillac to climb out of.

[@airplanes42]

I have a 2012 EXL-V6 Honda Accord that has turned cylinders on and off flawlessly for 12 years and 150,000 miles. How did any leader at GM keep their jobs during this time?

[@stormythelowcountrykitty7147]

Sounds like a good idea but not practical at least then.

[@antonchigurh981]

45 years later and GM still cannot figure it out.

[@cardiffchris]

IMHO 1977 to 1985 best looking Cadillacs of all time.

[@1940limited]

Agreed but the engine problems killed them.

[@pcno2832]

They should have gotten rid of the 6 cylinder mode and kept the V-4-8 until they had cars which were small enough for the 4100. They could have made up for the annoyances of the system with extended warranties and total deactivation for customers who insisted. Either would be better than an underpowered engine that won't stay in one piece. It could also have been a positive learning experience for GM and certainly a less painful one than the early 4100s. It must have taken an army of yes-men to get the 4100 approved when it was so obviously a disaster in progress.

[@The1cdccop]

Still better than the HT4100. You could at least deactivate the 8-6-4 problem, but the 368 was actually decent in its conception. The Aluminum block, cast iron head 4.1 was a disaster. Cadillac should have gone with the 350 Olds in all their models.

[@MarinCipollina]

They should have simply retained the 368 Cadillac engine

[@johneckert1365]

​@@MarinCipollinayes 👍

[@tombrown1898]

Cadillac sold a lot of Lincolns in those years.

[@avioncamper]

This engine did have the best GM transmission, the TH400. Cut the wire to the transmission, ran as a regular V8, after that was a great car. HT4100 that one was sad.

[@TheCarCrazyGuy]

They should have made a V8, 10, 12, lol

[@1940limited]

Yes!

[@EyesWideOpen61]

My buddy’s dad had a new one of these when we were in college, we used to love to screw around with it and watch the instant MPG readout go from 0 to 99 😁 That was a long time ago, but I still remember the six-cylinder operation was pretty crude.

[@Sedan57Chevy]

Ah yes, GM's favorite method for ruining an otherwise amazing, reliable V8- cylinder deactivation! The fact that this concept failed in 1981, and has continued to have so many issues even on the modern LS V8s, is really a major frustration to those of us who really typically like GM V8s.

[@zone47]

GM was amazing in the 50s and 60s. The 70s and 80s for GM was a mess thanks to our gov. I had to ditch them in 1980. The Japanese had an easy time taking over and I was pleased to finally drive a brilliantly engineered car.

[@RustyRench]

Just deleted my 2015 4.3 v6 in my silverado, it runs smoother and gets just as good of mileage maybe even better. It would shake and vibrate when in 4 cylinder mode, and will lessen the life of your engine.

[@earlanderson8245]

i think cylinder deactivation should be driver choice like a slap shift, both of those would be great in a vehicle.

[@maxr4448]

Our government should reward all companies who create efficiencies, at all methods of production and energy, instead Forcing Companies to Government standards. I never could understand why Our Federal government does this. Products like this cause problems for everyone. It still exists to this day. Just Crazy.

[@georgechambless2719]

Most Cadillac buyers back then wouldn't even consider a V6. Too bad it was the best engine available.

[@wavehogger]

Drove mine across the country both directions and averaged about 27mpg’s. It was a pain to keep working and the vibration in 6 cylinder mode didn’t feel great but it kept on going.

[@steveb7310]

I remember in 1980/81 on my short 10 mile commute to school, I would see about once a week a new Cadillac at the side of the road on fire. Also of course some very distraught individual standing as their beautiful new Cadillac burned.

[@unclerudy9797]

I was a Cadillac Master Craftsman when these were new... Mostly disabling the V8 64 systems... They failed regularly...

[@1940limited]

They only offered it 1 year. That should be telling. For the GM premier marque to have so many engine problems is pretty inexcusable. After 8-6-4 it was the disastrous HT4100 that couldn't be disabled.

[@kevineich5029]

The V8-6-4 continued on in the commercial chassis until 1984 or 1985.

[@AlexanderWaylon]

My mentor was a master collision tech refinisher, and was a used car man as a second form of income. He said he found that he filled his lot with Cadillacs in the mid 80s with engine issues. He said in the early 80s Cadillacs had devolved into merely a nice place to sit. Along with dozens of diesel Oldsmobile 88s and 98s, all of these bad Cadillac V864s HT4100s received used Oldsmobile 350s sourced primarily from rusted and crashed Cutlasses. They were a cash cow for him.

[@kroge007]

My Aunt and Uncle bought a 1981 Sedan DeVille. My Uncle complained so much about the engine (8-6-4). They would not keep it long before they traded it in for a Grand Marquis

[@Jeff_Pendleton]

On Vice Grip Garage, Derek did later get his 81 Cadillac running with a new ECM.

[@briancorreia2923]

Every current engine manufacturer that uses cylinder deactivation that I can think of has a problem with it. GM, Ram, and Honda. Not just drivability or vibration, but valve train longevity.

[@kalebbrown93]

Never understood why they did this goofy solution instead of just using that 350 olds gas engine out of the previous Seville. It made more power than this larger 368 and probably got better mpg than this silly solution.

[@deanstevenson6527]

To downgrade it's previously excellent Bendix derived Oldsmobile Electronic Port Fuel Injection to pi55 and Dribble Throttle Body Injection was the beginning of the problem for the 368. General Motors with the Cosworth Vega and 5.7 Olds and the 8.2 Liter, that Bendix system was successful on three different engine families, Chevy, Olds and Cadillac. Bendix merchandised Three different Port EFi systems starting, 1975. The roll out was on 121 cube 16 valve Vega(75), 350 Olds(76), and 500 Cadillac ( optional, 76 I think) and then as a continued option on the downgraded 425 Cadillac ( for 77-79). Somewhere, some one did a Budget cut move to TBi in the early 80's, and that continuous supply of fuel to disabled cylinders did the worst to the 368 Modulated Displacement V8. For GM to ruin the 368 ship, for a hapworth o' tar...tragic!

[@TeeroyHammermill]

That Bendix EFI wasn't really all that great. It was a crude analog computer that fired 4 injectors at 2 stages for a V8. Not very accurate and notably problematic. GMs digital TBI was far more reliable and lasted through the 1995 model year in light duty applications and maybe even longer or Medium duty trucks.

[@deanstevenson6527]

@@TeeroyHammermill 👍 The Old 5.7 had eight injectors, as did the 500 Cadillac. GM took charge, and replaced an external contracted 'Buy in' with its own Delco system. Eventually, with the 82 Cross Fire, a proven commodity that used the same basic ECM unit for TBi and Tuned Port EFi...but it was definitely a problem child in a modulated displacement engine, washing down the cylinder walls in redundant cylinders in 6 and 4 cylinder mode.

[@TeeroyHammermill]

@@deanstevenson6527 :Yea it was 8 injectors fired 4 at a time in 2 stages. Not very accurate at all.

[@deanstevenson6527]

@@TeeroyHammermill Duty cycle control. They fixed the ECM by 1979, the idle Fiddle Valve took a while to master, the sweep TPS injector enrichment sure caused a lot of no starts. GM did a lot better than the Bosch D-Jetronic that Citroën, Volkswagen, Volvo 164, early Mercedes Benz and Porsche 914, Saab 99, Toyota Crown and Jaguar XJ's were forced to use starting from 1967 to 1979. Those seven car makers fed massive amounts of information back into Robert L Bosch coffers, but they were even more difficult.

[@TeeroyHammermill]

​@@deanstevenson6527I've never drove a V864 car so I don't know what the problems were. There are a few videos posted on KZbin with owners driving them and they seem to be running fine. I've had 4 GM cars with the TBI, 2 were Cadillac DFI versions. The only problem I had was on my 88 DeVille with the ISC motor acting up setting a code E30. Other than that, the systems worked fine. Of course the fuel pump takes a dump between 75,000-90,000mi but that's just a GM thing that still persist to this day. Cheers

[@DSP1968]

A wonderful summary, Adam. I never had the joy of driving one and would have liked to just for the experience.

[@fomfom9779]

I have a V-6 3.5L engine in my Honda. And it switches between 3, 4, and 6 cylinders. Even though, it is all wheel drive, and weighs 4,000 pounds. It can cruise along at 70mph, with the AC blasting, and get 30 mpg. Stop and go traffic, is another story. It loves gasoline in those conditions. PS It has active motor mounts, and active sound control for the cabin, via the sound system.

[@Expatriate1977]

Ironically I’ll be daily driving a 1972 Cadillac DeVille soon. I don’t care the economy is not the best, I care about having something that is fun, comfortable stylish and cheap for parts and repairs. Being im a mechanic they are the best choice. If they were built to last 50 years then I would rather put in the time and money in them to last another 50 years. There’s no reason to buy a new car. They don’t last long and they cost a lot of money both in purchase price and repair costs. Automakers messed up. Bad

[@MarkWG]

I had a 1972 Sedan de Ville from 1977 until 1985. It had 21,000 miles on it when I bought it from an 80 year old lady. It was a daily driver from 1977 through 1980. Then, I bought a 1976 Sedan de Ville with 28,000 miles on it in 1979, that was a daily driver until 1985. I wish I had both of those Cadillacs back! The 472 and 500 engines were the best, reliable engines ever. In between, I also had a 1980 Seville, 1979 Fleetwood Brougham, and 1983 Eldorado. The 1983 Eldorado was a piece of pure shit with that horrific boat anchor, HT4100 lame engine.

[@cadillacnan]

I just returned home from being out all day ..1976 sedan DeVille. Runs absolutely perfect. Not a care in the world about fuel consumption. No computers,no bullshit in it. Just a big lump of heavy metal. God bless america

[@paulwindisch1423]

I love old cars, but I just don't agree with people saying new cars don't last long. Current vehicles last longer than ever before without much maintenance. Much longer than most old vehicles.

[@Expatriate1977]

@@paulwindisch1423 it’s because they are designed to die in less than ten years to force buyers to buy the newest car. Trouble is it’s backfiring and prices are out of control for new cars and they aren’t selling. In addition to this, they aren’t going to support cars after 8 years of production. Cars ten or more years ago were more supported and of higher el quality. They even made it so most new cars can’t have their engines rebuilt. Just too much to kill the bank account.