Feast your eyes on an engine that was never produced: a 1960s Cadillac V12 prototype. Here’s the story behind the story.
One great thing about publishing on the web is the ability to circle back and revise stories as more info and photos become available. This feature originally ran on June 27, 2012 and the time has come for an update. Thanks for reading. –MCG
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 in future products, with a approximate target date of 1967. Meanwhile, the Cadillac styling studio worked on design proposals with fabulously long hoods to accommodate V12 and V16 engines. MCG has seen two examples of this oddball V12 over the years and photographed this one on his regular visits to the Heritage Collection.
GM stylist Chuck Jordan with a Cadillac proposal
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. The block is cast aluminum, as are the cylinder heads. There’s a single overhead camshaft on each of the cylinder banks, which are split 60 degrees. Three Rochester 2GC two-barrel carburetors 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 1930-31, 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 General Motors LS V8 family.
The prototype V12 featured here never made it to production, obviously. When the 1967 Cadillacs appeared in the showrooms, they were powered by the standard Cadillac 429 CID V8, upgraded to 472 CID in 1968, then to a whopping 500 CID in 1970. And that ought to be big enough, one presumes. The slide show gallery below features original factory photos of the prototype V12 engine, details of the engine currently in the Heritage Collection, and some other items of interest.
Cool looking motor, although, I’d bet it gets 2 gallons per mile on gas. V-12’s were nothing new at GM in the 60’s, as I’m reminded of the Thunder 702 c.i. V-12 truck motor from GMC. At first glance, it looks like 2 V-6’s grafted together, but is also a one piece block with spark plugs down the top. It got pretty lousy mileage and was dropped after a few years, as diesels were coming of age. They are now a hit with rat rod builders, if you can find them, that is.
http://hooniverse.com/wp-content/uploads/2009/11/GMC-Twin-Six.jpg
I remember those GMC gas V12s well, worked on them as a tyke. As you say, there was a small market for such engines among those who just didn’t want diesels for whatever reason — fire depts, etc. Would make an interesting rat rod engine, must weigh 1500 lbs. Don’t know this but maybe (?) one of the Blastolene cars runs one.
I understood that 12 and 16 cylinder motors became redundant when technology allowed eights to be as powerful and reliable as the larger units.
The pictures show two different motors. Would that be the two different sizes?
The period studio photos are of a wood model, it appears.