1974 GM Big Block Specsby John Willis
General Motors developed a line of large V-8 engines referred to as "big blocks" because they replaced a series of relatively smaller V-8 engines. The larger engine blocks accommodated larger combustion chambers, producing more engine power. Combustion chambers are measured by the total volume of a cylinder, measured from the lowest point of the piston's travel to the highest point. The resulting "displacement" is multiplied by the number of cylinders to calculate the size of the engine. Larger engines require larger blocks.
GM produced two big block motors in 1974: the 427 and the 454. While the 427 saw more glamorous applications such as power Camaros and CanAm racecars during its earlier production run, in 1974, it was used solely in commercial trucks. That year, the term "big block" most often referred to the Corvette and its 454-cubic-inch, big block V-8.
Corvette 454 LS4 Big Block
While Corvettes were available with small block V-8s in 1974, including a 195 horsepower model, the engine most often associated with the Corvette brand was the 454, also known as the LS4. The 454 had a lower 8.25-to-1 compression ratio than the 9-to-1 ratio of small block counterparts but made up for it in sheer size with a bore of 4.251 inches and a stroke of 4.00 inches. Size wasn't all that set it apart from the small blocks. The LS4 was fitted with a high performance cam and Rochester Quadra-jet, four-barrel carburetor; this package produced 270 horsepower at 4,400 rpm and a more impressive 380 foot-pounds of torque at 2,800 rpm.
Other 454 LS4s
Corvette was not the only GM car to use the LS4 in 1974. This engine was also used in the Chevrolet, Monte Carlo and Chevelle. These "standard" non-Corvette LS4s had smaller cam profiles and produced 235 horsepower at 4,000 rpm and 360 foot-pounds of torque at 2,800 rpm --- 35 horsepower less than the LS4 in the Corvette.