Pontiac 421 engine
Pontiac 421 engine was a high-performance big-block V8 introduced in 1961, originally developed for NASCAR and drag racing before becoming available in production cars. Part of Pontiac’s “Super Duty” program, the 421 shared its architecture with the 389 and later 428 engines but featured a larger bore and stroke—4.09-inch bore and 4.00-inch stroke—for a total displacement of 421 cubic inches (6.9 liters). It was designed to deliver strong low-end torque and top-end power, making it ideal for both competition and street performance.
Early 421 engines were offered in limited production high-performance models with dual quad carburetors and heavy-duty internals, producing up to 405 horsepower in Super Duty trim. By the mid-1960s, Pontiac made the 421 available in full-size cars like the Catalina, Bonneville, and Grand Prix in both performance and high-compression street versions. It was a key part of Pontiac's muscle car legacy, laying the groundwork for future icons like the GTO. The 421 was phased out by 1967 in favor of the 428, but it remains highly respected among Pontiac enthusiasts for its torque-rich character and competition pedigree.
