The Corvette introduced a 427-cubic-inch big-block V8 for 1966. This Mark IV engine replaced the 396 offered during 1965 and gave the C2 Sting Ray a larger, more powerful big-block option for its final two model years.
The 427 was available in several forms, including a 390-horsepower version listed in the regular Corvette engine range. High-performance variants followed, most famously the L88, which was conservatively rated at 430 horsepower and built in very small numbers for racing-minded buyers. The 427 option also brought distinctive hood treatment to clear the engine’s taller hardware.
The 350 and 396 choices can cause confusion. The 350 was a small-block output rating rather than the new big-block displacement, while the 396 belonged to the 1965 model year. The 454 came later, becoming associated with the C3 Corvette in 1970. Thus, for a 1966 C2 Corvette, 427 is the canonical displacement answer.