When Chrysler developed the famous 1951 Hemi V8, did the automaker copy the 1949 Cadillac V8?
If you’re a hardcore car nerd and you enjoy poring over old technical materials as much as we do, you may have noticed something interesting about the original 331 cubic-inch Chrysler Firepower V8 introduced in 1951. Namely: A number of its dimensions and specifications are similar, even identical to Cadillac’s landmark overhead-valve V8 that came out in January of 1949.
For instance: The displacements of the Chrysler and the Cadillac are identical at 331.5 cubic inches. So are the bore and stroke at 3.815 inches by 3.625 inches. What’s more, the bore centers in the two cylinder blocks are also identical at 4.5625 inches. The connecting rods are exactly 6.625 inches long in both engines, and the crankshaft rod and main-bearing diameters are nearly identical as well. Also, both engines employ the innovative slipper-skirt piston design originated by General Motors engineer Byron Ellis, and we could go on. Hmm. That’s quite a stack of coincidences.
Of course, there’s one very obvious difference between the two V8s: the Chrysler features the company’s signature hemispherical combustion chambers, while the Cadillac employs the more familiar kidney shape, the setup we know today as a wedge head. And naturally, the Hemi’s combustion chamber layout requires a completely different valvetrain mechanism. From the cylinder heads up, the two engines are remarkably different. But in their lower ends, the Caddy and the Chrysler appear curiously similar, on paper at least.
We’re by no means the first to notice these striking similarities. There’s even a colorful bit of Motor City folklore that attempts to explain it. As the story goes, a group of Chrysler engineers allegedly borrowed a Cadillac ambulance from a Detroit funeral home one weekend early in 1949 and tore down the engine to reverse-engineer it. Allegedly. But as with so many tales of this nature, the original characters are never identified. There’s no first-hand info, or even second-hand. It’s a barber’s uncle of the neighbor’s second cousin kind of story. It seems more like urban legend than serious automotive history.
1948 Chrysler A182 Hemi V8 prototype
There are additional problems with the theory that the Chrysler V8 is a partial ripoff of the Cadillac. Officially at least, the 1951 hemi was the result of a well-documented development program within Chrysler that began in 1943-45 and produced a number of physical prototypes, including a 289 CID L-head V8 in 1945, a hemi inline six in 1947, and a 330 CID hemi V8 (above) in 1948. The process was detailed in SAE presentations and in a 2007 book by Chrysler engineer Willem Weertman, Chrysler Engines 1922-1998. It doesn’t seem credible that Chrysler, a company with proven expertise in engine development, would discard its own sizable investment in an engine program to plagiarize another automaker’s design.
Cadillac block at left, Chrysler at right
One more problem with the Caddy-Chrysler conspiracy theory: When you see both engines disassembled, it’s obvious that while the dimensions are similar, the physical components themselves are noticeably different. The Chrysler block, pistons, crank, and rods are not copies of the respective Cadillac pieces. They are novel designs. And it makes no sense to plagiarize an engine design and then redesign all its individual components. What’s the purpose?
So if the Chrysler hemi V8 is not a copy of the Cadillac, why are so many of its key dimensions identical? That’s a good question. If the Hemi’s short block was a knockoff of the Caddy, it would be a simple matter for Chrysler to cover its tracks by altering the specifications slightly. There seems to be something deliberate at work. The two engines differed in one key specification: While the Cadillac was rated at 160 hp, the Chrysler was rated at 180 hp. Were the Chrysler engineers giving a nod to their counterparts at General Motors? A shot across the bow, perhaps? We honestly don’t know. But we wish we did.
That’s a head scratcher fer sure.
According to some sources Cadillac began development of the 1949 engine back in the mid-thirties, however, introduction was delayed by WWII. So, there was plenty of time for Chrysler to get wind of Cadillac’s design elements long before the 331 hit the streets.
On the other side of the coin the similarities between the Cadillac 331 and the Chevrolet small block that came out in 1955 are remarkable due, no doubt, to the fact that the same guys who developed the Cadillac engine went on to bring the Chevrolet 265 into the world.
Having worked in the industry I can understand what happened.
A Caddy engine was selected due to what was seen as a target engine. It was evaluated on a dynamometer and a series of heads were made to evaluate the impact on output from the engine.
They found that the hemi chamber gave the biggest kick so they stuck with it and the block and components exhibited sufficient robustness that the stayed with sizes and components so the development time could be reduced. ($$).
Met a guy that was involved with the design and creation of the small block Chevy. He said the team was told to use existing parts where possible because of proven strength and low cast availability.
They used a lot of the parts from the existing straight 6 which reduced their expensive development time.
Personal opinion, but: the measurements are too close for coincidence, considering all the engines came to life in the densely-packed postwar Detroit manufacturing community, with suppliers on practically every corner, and many opportunities for loose lips.
In the immediate postwar era, overhead V-8s were the key to survival (to everyone but Packard, it seemed.) Chrysler had cylinder heads looking for a block, so, being able to shortcut the process a bit by cribbing some architecture proven in LeMans competition would be helpful to get the product in production ASAP.
Olds had its share of imitators as well, offering some dimensions and intake port design to Lincoln’s first V-8; Studebaker was copying homework at the time, too.
FWIW, TRJ had a few stories about vintage overheads, including the Hemi and Cadillac V-8s that are well worth seeking.
Obviously not a coincidence. That is the point of the story.
As an old paramedic, if the story about the Cadillac ambulance isn’t true, it should be!
I am a former auto executive from the 1980s and SAE auto engineers were always a “society” (I was an associate member with loads of contacts) …and news traveled about developments then. SAE engineers in the 30s, 40s and 50s certainly talked! It’s human nature. Each organization was aware of competitor’s engine development through competitive intelligence gathering.
BTW: The first Chevy 265 engines starved the camshaft of lubrication and had premature wear after 30,000 miles. Cadies, Olds, Studebaker, Chrysler hemi, and Dodge polysphere did not have such warranty issues on that magnitude. Engine programs tend to run parallel and development is a combination of study and testing.
Auto history is so interesting though!
What about the “ARDUN” conversion for the ford flat head. If I recall correctly, that was a “hemi” that sure looked very similar to the Chrysler setup.