Cadillac turned the automotive world on its head with the introduction of the 1915 Model 51 V8.

Cadillac was not the first to produce a V8, of course: Its many predecessors included Ader, Darraq, and De Dion. When WIlfred Leland decided in 1912 that the novel layout might be ideal for Cadillac, engineers Charles F. Kettering and Edward Deeds acquired a De Dion automobile from France and a Hall-Scott aircraft V8 from the USA for study.

Analyzing the strong and weak points of these early V8s, they settled upon a basic configuration, which Scotsman D. McCall White, a veteran of Daimler and Napier and an expert on high-speed engines, developed into a final production design. When the 1915 Cadillac Model 51 was introduced in the autumn of 1914, it became the first V8 to be built in serious volume. The V8 was a sensation and more than 13,000 were produced that first year.

While some historians have assumed the Cadillac was a copy of the De Dion V8, actually it was quite a departure, and it’s also very different from the familiar V8 designs we know today. The connecting rods were fork-and-blade, with one rod nesting inside the other on each cylinder pair (above). Though it may look odd now, this setup was commonplace in early V-type automotive applications and also in large aircraft engines including the Rolls-Royce Merlin, as it eliminated the need for cylinder offset.

Each cylinder bank was a one-piece iron casting with integral cylinders and head. These were bolted to a cast-aluminum crankcase 90 degrees apart, where inside was a single-plane, 180-degree crankshaft with three main bearings. Detachable cylinder heads were adopted in 1918, and this basic L-head package remained in production through 1927.

Both the intake and exhaust mainfolding were tucked between the cylinder banks with a one-barrel updraft carburetor at top center, creating a compact package for the time. Bore and stroke dimensions were remarkably undersquare at 3.125 by 5.125 inches, with connecting rods a full 12.5 inches long, limiting their swing to only 22 degrees per crank rotation.

WIth a total displacement of 314 cubic inches, the V8 tested out at an impressive 70 brake horsepower at 2400 rpm, or .22 hp per CID. In that regard the Cadillac was worthy competition for the 12-cylinder Packard Twin Six, which developed 90 hp from 424 cubic inches (.21 hp per CID). While the Packard made the greater statement, the Cadillac was the more practical proposition, outselling the Packard by more than four to one. Packard had thrown a subtle jab or two at its rival when Cadillac responded with its famous “The Penalty of Leadership” ad in the Saturday Evening Post on January 2, 1915.

The Model 51 V8 was actually an inch or two shorter than the inline four that preceded it. It was that important feature, in part, that led to a flurry of imitators in the next few years from Cole, Regal, Willys-Knight, and many others, who saw that a powerful V8 could easily fit in a standard four or six-cylinder chassis. That fad soon passed in favor of inline sixes and eights, and the American V8 wouldn’t become ubiquitous until the ’50s. But at Cadillac the V8 has remained a mainstay for more than a century now, through the revolutionary 1949 overhead-valve V8 to the current 6.2-liter Blackwing with 668 hp.