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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.


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New Driver

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.

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.  

New Driver

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

Pit Crew

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.


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 

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?  

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.

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.

Intermediate 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.