Feast your eyes on an engine that never existed: the 1967 Cadillac V12.
This engine that never was is on display at the General Motors Heritage Collection in Sterling Heights, Michigan. (GM’s private museum is not open to the public but offers tours by appointment to car clubs and other organizations. Click here for an MCG feature about the collection.) Six of these prototype V12 engines reportedly were built in 1963-64 to test the viability of the concept for the upcoming 1967 Cadillac Eldorado. MCG has seen two examples of this oddball over the years and photographed this one on successive visits to the Heritage Collection recently.
As the story goes, both 7.4L (452 CID) and 8.2L (500 CID) versions of the V12 were assembled, variously tuned to produce roughly 300 to 400 hp and 400 to 500 lb-ft of torque. There’s a single overhead camshaft on each of the cylinder banks, which are split 60 degrees. Three Rochester 2GC two-barrel carbs and a pair of six-cylinder distributors, one at the front of each cylinder head, handle the fuel and spark. A great deal of hand fabrication is evident in the prototype engine in the Heritage Collection, including yards and yards of heliarc welding.
Of course, Cadillac first offered V12 and V16 engines in 1929, and the company has periodically revisited the multi-cylinder concept ever since in an apparent effort to recapture the magic of the Classic era. Most recently, the 2002 Cadillac Cien concept
sported a Northstar-based V12 (story here), and the 2003 Cadillac Sixteen concept employed a V16 powerplant based on the GM LS V8 family.
The prototype V12 featured here never made it to production, obviously. When the 1967 Eldorado appeared it was powered by the standard 429 CID V8, upgraded to 472 in 1968, then to a whopping 500 CID in 1970. And that ought to be big enough, one presumes. Shown here is the proposed 1967 Eldorado V12, probably a clay or fiberglass pushmobile, not an actual running prototype. Here’s a slide show gallery of the prototype V12 engine in the Heritage Collection: