The 1964 Pontiac GTO’s V8 displaced 389 cubic inches. Pontiac built the GTO around its 389-cubic-inch V8, rated at 325 horsepower with a four-barrel carburetor and dual exhaust. The optional Tri-Power setup used three two-barrel carburetors and raised output to 348 horsepower.
The GTO was introduced as a $295 performance package for the Pontiac Tempest-based LeMans, rather than as a standalone model. It added heavy-duty suspension components, wider wheels, hood scoops, special badges and a floor-shifted manual transmission. Its combination of intermediate-car size and full-size-car V8 power helped establish the muscle-car formula.
A common mix-up is the 400-cubic-inch engine. Pontiac enlarged the GTO’s V8 to 400 cubic inches for 1967, while the 455 appeared later as a high-performance option. The 350 is also associated with later Pontiac and Chevrolet applications, but it was not the 1964 GTO’s engine displacement.