They say necessity is the mother of invention, and that was certainly true for the Tempest Trophy 4, one of the more unusual engines ever produced by Pontiac.

A few months ago at Mac’s Motor City Garage, we told the story of the 1961 Pontiac Tempest and its unusual driveshaft setup (See “Secrets of the 1961 Pontiac Tempest Rope Drive” here). Though we barely touched on it then, the engine in the Tempest was fairly unusual, too. Long story short, it was essentially the familiar Pontiac V8 cut in half down the middle, creating an inline four with its cylinders leaned over 45 degrees to the right. A slant four, if you will. Pontiac called it the Trophy 4.

The oddball engineering was driven mainly by the Tempest program’s tiny development budget, and it was inspired by an earlier experiment led by Pontiac engine wizard Malcom McKellar and crew. They had deactivated four of the cylinders in a standard Pontiac 389 cubic-inch V8, and to their mild surprise it could push a full-size Catalina sedan to better than 90 mph while still delivering reasonable fuel economy. With a new cylinder block and crankshaft, this same basic setup became the production Trophy 4. The new four-banger shared more than 120 components with the V8, including one complete cylinder head assembly, and better yet, it could be produced on the same transfer lines.  According to Pontiac general manager Bunkie Knudsen, the engine’s startup cost was “practically nil.”

There was a downside, of course. With its 4.060-in. bore, 3.60-in. stroke, and 194.5 cubic-inch displacement, the Trophy was enormous for an inline four, which made it a shaker. According to the old industry rule of thumb, a four larger than 2.5 liters (153 CID) will typically need a balance shaft for satisfactory operation in a passenger car, but there was no funding for such luxuries in the Tempest budget.

Pontiac’s alternative approach was to allow the Tempest’s bent driveshaft to serve as a torsional damper, quieting the engine’s formidable torque reversals. (A four fires only twice per crankshaft rotation, with the crank decelerating the rest of the time.) Also, the engine was supported at the rear solely by the driveshaft and transaxle assembly, isolating it from the body. Meanwhile, the front of the engine rested on soft rubber isolation mounts. John Z. DeLorean, Pontiac’s 36 year-old assistant chief engineer, remarked that the Tempest was a car designed around an engine mounting system. Was it smooth? Not by contemporary standards, but it was considered smooth enough for an early-’60s Detroit compact.

The Trophy 4 was offered in five different horsepower ratings for 1961, from 110 hp (one-barrel carburetor, 8.6:1 compression ratio, regular fuel) to 155 hp (four-barrel carb, 10.25:1 CR, premium fuel.) For 1962-63, there was a four-barrel, high-compression package with 166 hp at 4800 rpm, but that would be the end of the line. When the Tempest was moved up to the intermediate class for 1964, Pontiac dropped the Trophy 4 and adopted a 215 CID version of the familiar Chevrolet inline six.