Pontiac management decided not to retain it due to slow sales—six-cylinder Pontiacs had accounted for only around 10-15% of volume since 1951. The traditional "Silver Streak" appearance five-chrome strips running down the hood and trunk were updated with a twin-stripe design. The biggest change for 1956 was again in the engine. The new for 1955 V8 was drastically enlarged to . Horsepower made a considerable increase, jumping to 192 and 205 respectively. Otherwise, the 1956 model Chieftains received only minor updates. A padded safety dashboard was added as an option. Sales for 1956 fell off by as much as 20% over record-setting 1955, in part due to tighter credit guidelines instituted by American banks that year. New "Star Flight" styling graced the 1957 Chieftains. This new theme included missile shaped side trim, extended rear fenders with V-shaped tips, lower hoods and massive bumpers. A new Super Chief sub-series debuted within the Chieftain line. These were the meant to be the top-of-the-line Chieftain models. Sales were 58.02% of all Pontiacs in 1957. The first "Tri-Power" Pontiac engines were offered. Once again the Pontiac V8 was enlarged. The 1957 model year saw the engine increase to , with horsepower increasing to 290 for the Chieftain models. This generation didn't experience the popularity as much as the Chevrolet Tri-Five during the same years, even though the models were very similar. Australian production The 1957 Pontiac, badged as the Pontiac Super Chief, was also assembled in Australia, by General Motors-Holden. Third generation (1958) Chieftains went through another major styling change in 1958. All models were given honeycomb grilles, quad head and tail lamps, concave rear fenders. The Super Chief sub-series was promoted to full model status leaving just the standard array of Chieftains as the entry level Pontiac. The "Sportable" transistor radio became an option (a portable, removable radio), along with air-suspension and a limited slip differential. As in years past, the V8 engine was enlarged. For 1958 it grew to and made and depending on version. The 1958 models were the last Chieftains to be produced. It was replaced with the all-new Catalina in 1959. References Chieftain Rear-wheel-drive vehicles Full-size vehicles Coupés Convertibles Sedans Station wagons 1940s cars 1950s cars Motor vehicles manufactured in the United States