In the mid sixties, Cadillac gave very serious thought to replacing its aging V8 engine with an OHC V12. And blog.hemmings finally convinced Cadillac to send them some detailed pictures and more information. Looks mighty production ready, but that air cleaner sure makes it looks a lot less sexy than a Ferrari with a bank of Webers.
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 two-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.
The engines were planned to make their appearance in the new FWD Eldorado in 1967. Ironically, one of the main reasons they were canceled is because GM drivetrain engineers were still considering a transverse orientation for the FWD system. That would have made the V12 too long. In the end, a longitudinal FWD system was used, which would have accommodated the V12. So the V12 appears to be a victim of poor GM planning.
One of the prototype engines is now available for your viewing pleasure at the GM Heritage Center.