Big, Big Cadillacs: IMSA Cadillac Prototypes And The Biggest Cadillacs Ever

Greg Zyla
Q: Greg, I’m retired and a lifelong Cadillac fan. Can you give an update on their auto racing teams I see on TV? I’d also like if you could tell a little about the many historic Cadillac engines and the overall biggest Cadillac ever? Also, do you think Cadillac should receive some credit for today's variable deactivation engines as they were the first modern cars to introduce the V8-6-4 in early 1980s? Thanks, I enjoy your column very much. Jim L. Danville, Pa.
A: Jim, I’m happy to help so let’s get started.
As the brand did from the very beginning, Cadillac still builds some of the finer road cars in the world, and they indeed do compete on the world stage both with their road vehicles and racing cars.
I’m especially happy you are aware of Cadillac’s motorsports involvement, as their top flight Daytona Prototypes compete regularly on the IMSA WeatherTech Championship road racing series. Included on the IMSA schedule are the Rolex 24-Hours at Daytona; Sebring 12-Hours in Florida; Sahlens 6-Hours of Watkins Glen; and 10 other multi-day events. IMSA events appear at major venues like Lime Rock, CT; Mid Ohio; MotorSport, Canada; Belle Isle, Detroit; Road Atlanta; Virginia International; Laguna Seca, CA; and more.
In addition to the Daytona Prototypes and LeMans Prototype (the latter a smaller version), three more GT style classes featuring Acura, Corvette, Audi, Ford, Porsche, Aston Martin, Ferrari, Lamborghini and many more compete at the same time with the prototypes. Support races for smaller bore cars compete during three and four day events and are also top attractions. So, with numerous different cars and manufacturers taking the green for the feature event, it’s perhaps one of the best kept motorsport secrets currently being offered.
The mid-engine Cadillac prototype race cars are world class vehicles with roaring V8 Corvette/Cadillac style engines for power. I just attended the Sahlens 6-Hours of The Glen at Watkins Glen, N.Y., and highly recommend you check out this style of racing at If you want more info on these Cadillac prototypes and the entire IMSA series, check out for more. It’s today’s fastest growing sanctioning body and the races in New York and Connecticut are closest to you, geographically.
Now, on to some of the biggest Cadillacs and their engines.
Cadillac’s history is loaded with lots of big, bigger and biggest engines. Specifically, the biggest Cadillac engine up through 1970 was the 472-cubic-inch V8s that became available in the Deville and Fleetwood models from 1968 through 1974. However, Cadillac went even bigger when it introduced the gigantic 500-cubic inch V8 in the 1970 Eldorado line. In 1975 and 1976, the Deville and Fleetwood line also featured this same 500-inch V8 before downsizing occurred in 1977. They way things are nowadays, IE: smaller bore engines with more power; I doubt there will ever be a Cadillac engine in the future that exceeds that 500-incher.
Of course, Cadillac has always been an innovative, luxury car company featuring different engines. Back in 1930, Cadillac offered a 353-inch V8, a 368-inch V12, and a 452-inch V16 all in the same year. In 1936, two new V8s joined the V12 and V16 offerings in 322- and 346-inch designs. Then in 1937, only one V8, a 346, was available along with the larger V12 and V16. In 1938, Cadillac dropped the V12 and reduced the V16 to 431-inches. The V16 lasted through 1939, and was then replaced by V8 engines only.
As for wheelbase and large cars, those 1975 and 1976 500-inch V8 models carried the same 130-inch wheelbase that first appeared back in 1959. (See photos). However, the longest wheelbase standard Cadillac, (not counting Limousines, stretched Fleetwoods or Sixty Specials) was again the 1930 Cadillac, which arrived at dealer showrooms riding on a 140-inch wheelbase. To this day, it remains the longest standard size Cadillac ever built.
Let's finish with the V8-6-4, which Cadillac produced from 1981 through 1985 with not much success. These engines were 368-inch V8 designs, and as highway and freeway speeds were reached, the cylinders deactivated from 8 to 6 and then to 4. Today, this is exactly what modern cars do be it a V8 or a smaller engine. The difference is that today’s modern marvel engines do the deactivation trick with flawless ease, something Cadillac struggled with in ’81. There were several reasons for the misfortune, including software not being up to the task combined with the new fuel injection systems that replaced carburetors. These engines were trouble prone and eventually removed entirely from production by 1986. However, Cadillac sure did have the right idea, so I do give them credit for trying something different 38 years ago.
Hope this all helps, Jim, and thanks for the nice comments. Make sure you check out those IMSA Cadillacs. 
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