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Bryan
Hagerty Employee

Why GM’s V-12 “Engine of the Future” never made it to production

Sixty years ago, General Motors was nothing like the company you know and (maybe) love today. In the 1960s, the firm was well-stocked with the industry’s smartest designers, engineers, sales experts, and division managers. No technical hurdle was too high, no engineering feat too far-fetched, for the colossus that bestrode more than 50 percent of the market and had no Asian competitors to fear. So when someone raised a hand and suggested that a nice, fresh V-12 engine would add luster to Cadillac’s prestige, there was broad consensus and no fiscal concern.

 

Read the full article on Hagerty.com:

https://www.hagerty.com/media/automotive-history/why-gms-v-12-engine-of-the-future-never-made-produc...

33 REPLIES 33
Stepwilk
Pit Crew

I suppose you could also consider as precedent the tens of thousands of V-1710 Allison V-12s built before and during World War II by GM's Allison Division, though of course they were in an entirely different displacement and horsepower class.

TrustyRusty
Intermediate Driver

Ah yes, the wonderful Allison V-1710.  It had a 5.25-inch bore and a 6.0-stroke, displacing 1710 cubic inches.  After World War Two, they could be had for pennies on the dollar.  A few adventurous long-haulers put them in semi trucks, but the fuel consumption made them prohibitive to operate.  They excelled, however, in unlimited hydroplanes and were used until quite recently in those speedboats.  A young, Art Arfons, built his original "Green Monsters" using Allison engines.  The WW2 P-38 Lightning used two contra rotating, TURBOCHARGED Allison V-12s in the enigmatic fighter.  The first aerial "kill" of the Korean War was made flying a Twin Mustang P-82, which was powered by an Allison V-12 in each of its two fuselages.  In addition, WW2 "PT Boats" used three Allison V-12 engines, housed in a lightweight, plywood hull...VERY FAST!  Eventually, Detroit Diesel (GMC) built truck and marine versions of the 12V71 and -91 series of engines.  So, General Motors has a ton of experience with building V-12 engines.

35-709
New Driver

My '73 Caribou (Coupe de ville) has a "501" 472 engine.  "501" is the engine SERIES, not the cubic inch measurement!  Many uninformed think they have a "rare" 501 cu. inch engine in their Cadillac because the emissions sticker lists it as a "501" but, again, that only refers to the engine "series".   The late '70s Cadillac 425 is also a "501".
Some other of today's auto uninformed think that Cadillac was using a Chevrolet engine back then (as we find today) and believe it is a 502 Chevy engine --- not so.

Sorry to see a Hagerty writer perpetuate the 501 myth.  

Michbc3
New Driver

According to Wikipedia the S code engine is listed as having 500 cubic inches of displacement in 1975.

Oldimpala
Intermediate Driver

I've laid hands on and worked on many 500ci Caddy motors. They're Cadillac 5200-series motors, and still fairly common (great torque, meh breathing, few performance parts) around junkyards.

They exist, along with the 472 and 425. Unless you're restoring a Cad (or want something odd), though, they're a tough sell.

Jos72st1
Passenger

Im wondering how much the block casting process and alloy share with the 215 buick v8 . Back in the day few people modded that engine to get over 300 hp ,Poston buick , and kenne belle offered speed parts . The heads flowed nice from the factory and headers really woke that engine up along with a longer run intake . I had a 62 special that would melt the pavement with a slightly modified switch pitch 300 trasmission . 
when I needed a head gasket it was impossible to find in 1980 . Finally someone looked it up in a Land Rover catalog !!! Turns out that block was used for many years by them 

Will
Intermediate Driver

It's not a myth. I've seen them labeled/badged as 8.2 liter as well, and that converts to 501 Cubic Inches.  1970 Eldorado, look it up. 

 http://www.1001moteurs.com/performance/view-Cadillac-Eldorado-8-2-8788.html

 

DougMeyer
New Driver

Don, Was the Acurad different from the Reynolds 390? As a CAN AM engine builder (Shadow) in the early 70's, we worked with Reynolds through GM. Alloy questions were always directed to Reynolds, not GM. But that work and subsequent work (Vega) came to the consumer via GM.  I guess I'm asking... Are Acurad and Reynolds 390 the same thing?  

GRSchultz1st
New Driver

I believe the Acurad process was finally put into a production engine for the 1971 Chevrolet Vega. While I recall that there were some cylinder wear reliability issues initially they did ultimately get it figured out. I had an early model Vega and when I blew a head gasket at almost 50,000 miles I was impressed that there was no ridge at the top of the cylinder at all.

DougMeyer
New Driver

 

Thank you. That's an interesting factoid. During the period 1971-74 I worked with the 390 blocks daily. Later, still working with the late Lee Muir, I worked with the alloy on an aircraft engine project for 7 years. Have a look at the April, 2019 issue of Victory Lane Magazine for a full description of that program- "When the Can Am flew".  Regarding the Vega, It had  (I think) a bad rap for sure. We felt the problem with the Vega was the open deck which precluded sufficient cylinder stability and allowed the cylinders to "move around", killing the head gasket and ring life. At the race team we had a Vega GT with the Cosworth head from GM as our parts getter. You can  imagine how that car was operated by a bunch of 24 year old Can Am mechanics. It never broke, and I remember it with a smile.  

 

 

GRSchultz1st
New Driver

Doug, Acurad was the name of the process GM created to improve the castings. Reynolds 390 was the aluminum used in the process.  I was a student at GMI at the time and recall watching a movie GM made about the process. Acurad stood for accurate + rapid + dense and IIR what it basically did was injected the aluminum at a much higher pressure than typical at the time.

OldCarMan
Advanced Driver

There was a place called M & R Salvage on Davison Ave. in Detroit that purchased leftovers and scrap from the Big 4 OEMs. About 1970, while looking for parts for my hot rod 32 Plymouth roadster. We saw an aluminum cylinder head that looked pretty cool. I was using a 1949 Cad engine with 57 heads and the clerk told us that this was a Cadillac cylinder head. That's when we noticed that there was 6 plugs in it and he said it was for a new  V-12 Cadillac engine. He didn't have the block or any other parts and wanted what seemed like a lot of money at the time for something you couldn't do anything with. It was many years later in a magazine article and later at the GM Heritage Center that I could actually see the real deal. This was an interesting dead end, but not at all surprising, given GM's market share and success at the time.  

35-709
New Driver

"The Caddy 429 was the last of the 50’s engine family, ending in 67. In 68 the 472 was introduced and was a totally new family, 1970 is when they increased the 472 to 501 inches, on Eldorados with the 501, the fender badge said 8.2 Litres. In 77 they decreased the 472 down to 425 and then again to 368 in about 1980." 

 

Once more, the 472 was increased to 500 cubic inches NOT 501.  The 501 number designates the engine series.  The 472, 500, 425, and even the 4-6-8 368 were all "501" series engines.  This mistake/misconception (whatever you want to call it) has been going on for years and I guess, like many old wive's tales, will continue.   

RustynutNbolt
Passenger

Hello, is M&R salvage still in business? I would love to check it out. 

stevecobb45
Detailer

A friend of mine, back in the early 60's, drove a GMC V12 powered semi truck. It was supercharged too. One night on main street in Shortsville, NY, he pulled out in the middle of the street (cab only) & proceeded to lay four streaks of smokin' rubber until nearly out of sight. Our jaws dropped & everyone said, "what's he got in that thing?".

wahip1
New Driver

While bragging rights offer some justification and the V-12 may have offere

wahip1
New Driver

While added smoothness, (debateable) and bragging rights may have justifed a V-12, there is little reason to add more weight and complexity to gain similar performance. Anyone who's ever driven both the six and twelve cylinder Jaguar XKE, immediately realizes that the six is both faster and better-handling. The extra 10 hp, being more than offset by the lighter car.

Punk
Detailer

Re: Jag's XK engine (6 cyl) and the V-12, the 6 WAS faster in the early 1960s. But by 1971 when the V-12 debuted, emission and other requirements made it really slow down. By contrast, the V-12 in 1971 was a very fast, turbine smooth engine with a huge increase in torque and hp over the 1970 XK engine, although not much more than the XK was producing in 1961 when the E Type debuted. I have owned both 12 and 6 cyl E's and I prefer my early car, but the 12s were fabulous and a huge step up at the time.

cammerjeff
New Driver

Interesting engine, last fall while visiting the Heritage center I was able to see 2 examples of this engine, one restored cosmetically, and the other looked like it was just unbolted from a dyno or test mule. No one working at the time could tell me anything about it other than what was printed on the restored engines Placard.

 

Thanks for posting it. I wonder if the cam followers were the same as used in the Pontiac OHC6 or maybe the Vega 2.3?

RoadTest
New Driver

Fact check:

The displacement of the FWD Eldorado (1967) was 429 cid. That's 7.0 liters. Not 8.2 liters (which equals 500 cid.) 

 

The 429 in the '67 Eldo was the standard 340 hp engine (except for the EPP special parts) that the rest of the Cadillac line used. 

 

In 1968, Cadillac's V8 was enlarged to 472 cid (7.7 liters) and produced 375 hp.  The Eldo shared it (minus the EPP components) with the rest of the line.

 

In 1970, it was enlarged again to 500 cid (8.2 liters) and 400 hp.  (It was an Eldorado-only engine, that year.) 

 

The rest of the division continued to use the 472 until 1975, when the 500 cid was installed in all Cadillac models.  Compression ratios were lowered across-the-board in 1971, leaving the 1970 Eldorado with a one-year-only high output of 400 hp. 

nope
New Driver

And the Toronado started it's life with a 425 cid engine, not a 455...

RoadTest
New Driver

UPP...not EPP.  Typing too fast. 

TwinHman
New Driver

The Caddy 429 was the last of the 50’s engine family, ending in 67. In 68 the 472 was introduced and was a totally new family, 1970 is when they increased the 472 to 501 inches, on Eldorados with the 501, the fender badge said 8.2 Litres. In 77 they decreased the 472 down to 425 and then again to 368 in about 1980. 

Dano1953
New Driver

Two other deadbeat GM engines that should have never been built:  GM diesel and the V8-6-4.  

RoadTest
New Driver

Cadillac engine history:

 

The Cadillac 331 engine that debuted in 1949 was eventually enlarged to 365 and 390 cid, and continued through 1962.

 

In '63, Cadillac redesigned the engine to be lighter weight, but kept the 390 cid displacement. 

 

In '64, they enlarged the engine to 429 cid.

 

That engine became the 472 in '68, the 500 in '70, and the 425 in '77. 

35-709
New Driver

"In '64, they enlarged the engine to 429 cid.

 

That engine became the 472 in '68, the 500 in '70, and the 425 in '77. "

 

The 429 absolutely did not become the 472 engine in '68.  The 472/500/425 (all 501 series engines) were a fresh design of new architecture and were a far better engine.  

DougL
Intermediate Driver

I own a Jaguar XJS V12. Most of what is said here applies to that engine also. No real power advantage over other engine designs, but a noticeable fuel mileage penalty. But the V12 is very smooth, more so than any V8 I have driven, and has a unique sound. Perhaps those are reasons enough. 

Steveduck
Passenger

Love to know what sort of MPG it takes to power these monsters.

SS 

TG
Detailer

It would be interesting to know some of the science behind why these V12s underperformed and drank more fuel

That thing would have looked very impressive under the hood of an Eldo

RoadTest
New Driver

Correction noted.  The 472 was more than a poked & stroked 429, but I would not refer to it as a complete redesign. Many maintenance items were improved and it was slightly smaller in exterior dimensions.  However, it also weighed around 80 pounds more than the 429. 

 

The 1964-67 429 was a plenty stout performer. I've owned five low-mile Caddys:  '61 CdV, '64 Eldo, '64 SdV, '67 Fleetwood, and a '70 Eldo.  They were all under 30,000 mile original cars, with the '64 SdV being a 14,000 mile one-previous-owner gem.

 

I owned these cars at the same time, so it was easy to make real-world comparisons.  The 1967's had the switch-pitch torque converter with the Turbo 400 that made rubber-peeling starts an easy feat. 

 

The 472 and 500 were torquier than the 429, for certain, but my '67 Eldo was very close in performance to the '70.  Both cars were completely stock, and properly tuned.  The '70 would smoke the tires a bit further, though!

 

I actually preferred driving the '67 Eldo, mostly because its interior was nicer. The dashboard and door panels were considerably cheapened in 1969-70. 

 

I grew up with Cadillacs of the '60s and '70s, and have logged a lot of miles in them.   

For my money, my favorite years of Cadillac are 1964, '67 and '68.

 

RoadTest
New Driver

Forgot one in my "Cadillacs owned" count. I had a black '67 Eldo with around 19,000 miles.
Brad
Hagerty Employee

I've got a thing for Big 'Ol Engines, and this was a great read- thanks, Don! I do love that old "twin six" GMC V12 truck engine, it's got a unique look!

FOG
Passenger

Because GM doesn't do ANYTHING cool or innovative today... Not Ultium batteries... Not muscle cars that run with sports cars... Not a Hummer SUV with removable body panels... Not a $200K, hand-built Cadillac halo... Not highly desirable supercharged and turbocharged Cadillac sedans... Not highly desirable trucks and SUVs... Not automated driving, or one of the world's first automated pods... Not bringing a mid-engine sports car to the masses.... The first affordable EV... But hey! They used to be innovative, because V12 prototypes! (insert eye roll here)