Automotive History: The OHC V12 Engine That Cadillac Almost Built

Cadillac V12 a

Imagine lifting the hood of a 1967 Cadillac, and seeing this alloy SOHC V12 nestled there. It’s hardly a far-fetched notion. In the mid sixties, Cadillac came very close to replacing its aging V8 engine with a modern OHC V12. There have been references to this program, but there was almost no photographic evidence of these intriguing engines. A while back, blog.hemmings finally convinced Cadillac to send them some detailed pictures and more information.

CadV12atHeritageCenter_1000this one is at the GM Heritage Center

Six prototypes were built in 1963 and 1964, all with a 60-degree bank, chain driven camshafts and hydraulic finger followers. The initial displacement was 7.4 liters, but an 8.2 was also built, which corresponds exactly to the size of the new V8 engine that eventually was built instead of the V12. Various induction systems were tried, including single four-barrel, dual four-barrel, and triple two-barrel carburetors, as well as fuel injection. Output was between 295 to 394 horsepower, and from 418 to 506 lb.ft. of torque.

CadV12_02_1000

According to historian Karl Ludvigsen, the V12 engines were planned to make their initial appearance in the new FWD Eldorado in 1967. GM drivetrain engineers at that time were considering a transverse engine orientation for the FWD system, and protested that the V12 would be too long. But supposedly they then relented, and switched to a longitudinal FWD system which could have accommodated the V12. But then the V12 program was killed, “due to the poor performance of the test engines and due to a predicted inability for the engine to meet anticipated emission controls”

What seems odd to me about that statement from Ludvigsen is that I have never heard of GM’s Toronado FWD program considering transverse engines, as Olds had been working on FWD prototypes since 1960 or earlier, and to the best of my knowledge, they were all longitudinal. Certainly Cadillac couldn’t have been considering their own FWD system; that just makes no sense.

As it turned out, the V12 died for other reasons. But it sure makes for fascinating speculation to think of a whole generation of Cadillacs with V12s under their hoods. It came mighty close to happening.

due to the poor performance of the test engines and due to a predicted inability for the engine to meet anticipated emissions controls. – See more at: http://blog.hemmings.com/index.php/2010/04/14/success-cadillacs-ohc-v-12-engine-photos-found/#sthash.NkfBMmh6.dpuf
the poor performance of the test engines and due to a predicted inability for the engine to meet anticipated emissions controls. – See more at: http://blog.hemmings.com/index.php/2010/04/14/success-cadillacs-ohc-v-12-engine-photos-found/#sthash.NkfBMmh6.dpuf
the poor performance of the test engines and due to a predicted inability for the engine to meet anticipated emissions controls. – See more at: http://blog.hemmings.com/index.php/2010/04/14/success-cadillacs-ohc-v-12-engine-photos-found/#sthash.NkfBMmh6.dpuf

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