Pontiac GTO Tri-Power 389

Pontiac GTO Tri-Power 389

The 1966 Pontiac GTO Tri-Power 389 represents the final year of the original GTO's most iconic engine configuration. General Motors' corporate decision to ban multiple carburetor setups after 1966 made this the last GTO to offer the legendary three-deuce (Tri-Power) induction system, ensuring its place as one of the most collectible muscle cars ever produced.

For 1966, the GTO graduated from an option package on the Tempest to a standalone model in the Pontiac lineup -- recognition of the car's enormous commercial success and cultural impact. The new status brought minor styling revisions including a revised grille design, new side trim, and updated interior treatments, but the fundamental formula remained unchanged.

The 389 cubic inch V8 with Tri-Power carburetion continued to produce 360 horsepower, the same rating as the 1964 and 1965 models. The triple Rochester two-barrel setup remained mechanically unchanged, with the center carburetor handling normal driving duties and the outboard pair opening progressively under heavy throttle demand. The result was a power delivery that combined docile everyday behavior with explosive acceleration when the secondaries opened.

The four-speed Muncie manual and two-speed automatic transmission options continued from previous years. The Muncie M21 close-ratio gearbox remained the enthusiast's choice, while the M20 wide-ratio version was more suitable for highway cruising. A Hurst shifter was available as a dealer-installed option.

The 1966 GTO benefited from continuous chassis refinement that had occurred since the model's 1964 introduction. The front suspension's unequal-length control arms with coil springs and anti-roll bar were tuned for improved turn-in response, while the rear coil-spring live axle arrangement provided a more controlled ride than the leaf-sprung competitors.

Braking remained the GTO's weakest area, with standard four-wheel drum brakes that were marginal for the car's performance capability. Front disc brakes were available as an option and are highly recommended for safe enjoyment today. Power assist was also optional.

The 1966 GTO's styling achieved a more refined, mature look compared to the 1964-1965 cars. The stacked quad headlights, revised grille pattern, and cleaner body lines gave it a sophisticated presence that matched its standalone model status. The available Rally II wheels with redline tires provided the perfect visual accent.

The interior received upgrades including improved materials, a new instrument panel layout, and available woodgrain trim. The standard bucket seats and floor-mounted shifter continued to create a sporting atmosphere.

1966 was the peak of GTO production, with 96,946 units sold -- a figure that demonstrated the muscle car market's explosive growth. However, the Tri-Power option was ordered on only a fraction of total production, making these cars relatively rare.

The 1966 Tri-Power GTO's status as the last of its kind has made it one of the most sought-after Pontiac muscle cars. The combination of the final Tri-Power engine, the mature 1966 styling, and the GTO's historical significance creates a car that resonates deeply with American performance car collectors.