The Tempest compact helped make Pontiac the third best-selling U.S. marque of the 1960s, and the GTO confirmed its performance credentials: It was a real hot rod. Completely restyled intermediate models and an allnew 6-cylinder engine topped the news from Pontiac for 1966. An exotic (for the times) new Overhead Cam 6-cylinder engine was implemented as the base powertrain in the Tempest and LeMans lines.
This type of engine, normally found in for more exotic European models, had not been offered in a modern American car until now. The overhead cam design offered more horsepower from a smaller displacement engine. In fact, the power was equal to many smaller V8 engines, but it was more economical to operate. This engine also offered a 4-barrel, high-output variant that would be quite popular with budget-minded performance types. Elsewhere while still using many of the 1964-65 years parts underneath, the new Tempest, LeMans and GTO models now had styling that more closely resembled their big brothers. Body sides were smoothed and rounded, and the style-setting vertical headlamps were set into fenders that were now straight up and down at the leading edge, instead of canted forward.
This year also marked a significant landmark in the GTO history. For 1966, the GTO became its own model, no longer just an option package. The line consisted of the 2-Door Sport Coupe, 2-Door Hardtop and a 2-Door Convertible. The new marketing ploy worked, and sales of the GTO increased about 30 percent over the previous year. Unfortunately, this would be the best year the GTO would see for sales. In the other intermediate lines, a new 4-Door Hardtop model was added for the Tempest Custom and LeMans lines. In the LeMans line the Hardtop had replaced the 4-Door Sedan model.
In the full-size lines, styling changes included revised front ends and taillamp styling. Also the 2 + 2 was marketed as a separate model, but only for this year. The only other significant model change was made to the newly named Star Chief Executive line. In an attempt to revive sales in this mid-range model line, a 2-Door Hardtop was brought back, and the Executive name was added. This was done as a cross-over measure to give some continuity to the line, but it would be simply the Executive by 1967.
The Star Chief name had run its course and was the final link remaining in the Pontiac line to its pre-1957 days of Silver Streaks and chrome "star" body decorations. This was also the final year of production for the famous 389 CID V8. Putting this engine into the intermediate size platform and creating the GTO had set into motion the whole muscle car movement, and it would be a sad passing for many Pontiac enthusiasts. However, in its place was a similar engine with slightly more cubic inches, the new 400 CID V8, and it would prove to be just as legendary in the years to come.