When the final 1954 Packard rolled off the line, it marked the end of the straight-eight epoch in the Motor City.

Packard didn’t invent the straight-eight engine, of course. The cylinder layout is obvious, natural, and nearly as old as the automobile itself. But it was a signature Packard feature for decades, starting with the 1924 Single Eight and its innovative two-plane crankshaft design. (Read about the Single Eight here.) While the automaker on East Grand Boulevard also offered a fine inline six and a mighty V12 Twin Six, among others, the inline eight was Packard’s most popular engine through most of the company’s history.

Through these years, most of the Motor City’s automakers, from Buick to Hudson, also offered straight eights in their premium car lines. (Cadillac and Ford were two rare exceptions with their V8s.) But by 1954, only two straight eights remained in the American car market: Packard and Pontiac. And for 1955, they were gone, replaced by the ubiquitous overhead-valve V8.

This 1938 120C, above, is a typical example of Packard straight-eight engineering.  Featuring a conventional cam-in-block, L-head layout like all Packard eights, the 120C displaced 282 cubic inches (3.25-in. bore x 4.25-in stroke) and developed 120 horsepower at 3800 rpm. Advantages of the inline eight include straightforward design, a narrow footprint, and natural smoothness, due in part to the eight firing impulses per operating cycle, four with each rotation of the crankshaft. Packard’s inline eights were renowned for their quietness and long operating life. It’s been said that the old chauffeur’s trick of balancing a nickel on an engine at idle originated with the Packard eight.

Along with the benefits, the eight-in-line layout had some natural drawbacks as well. The cylinder block and crankshaft were extremely long, and as a result, had to be massively constructed to maintain sufficient rigidity. So the straight eight was not just considerably longer than a comparable V8, it was also significantly heavier—by hundreds of pounds in many cases. And as time went on, these twin burdens of length and weight grew more problematic every year. Through much of the Classic Era of 1925-1948, the straight eight was a perfect fit for the long hoods then in style, but by 1954, a more balanced profile was was in vogue—for example, in the 1954 Corporate Limousine above. Even in this massive vehicle, the straight eight was not an efficient package.

For Packard’s final year with the straight eight, the company actually offered two distinctively different engine families. The smaller of the two, featuring a five main-bearing crankshaft, was offered in two sizes, 288 CID and 327 CID, and three output ratings: 150, 160, and 185 horsepower. The senior Thunderbolt straight eight, shown above, sported nine main bearings and a displacement of 359 cubic inches, and was rated at 212 horsepower.

With hydraulic valve lifters, a Carter four-barrel carburetor, an aggressive (for an L-head) compression ratio of 8.7:1, and better than 200 horsepower, the mighty Packard straight eight was, on paper at least, a competitive match with the new and advanced V8s from Cadillac, Chrysler, and the rest of the industry. But in truth, the Packard eight was at the end of its development life, and the high-compression V8s were only beginning to show their potential. For the 1955 car season, Packard retired its inline eights for good and introduced its own overhead-valve V8.