Pontiac Trans Am 1970 to 1975
The second generation Firebird was late because of tooling problems; the car did not hit the showrooms until February 26, 1970. The sales literature from late ’69 early ’70 is unique because it has no date mentioned and a diligent collector will refer to the “Firebird 1969 ½” as a separate model.
The new generation Firebird has a swooping body style with a long rear window extending almost to the trunk lid. The weight of the car went up because of the newly integrated safety laws and structural changes to strengthen the body and frame. The 1970 had a different body style but the power options were the same as the previous years; however the 1971 model offers a 455 cu in (7.5L) V8 the – 455 H.O. option which is continued through 1973.
Two additional engines were added in 1970 – the Ram Air III producing 335 hp (250 kW) and the 345 hp (257 kW) Ram Air IV. Those horse power ratings are actually for the GTO version of the Rams and the Firebird can achieve the same ratings by bending the carburetor linkage and allowing the carb jets to open fully
The 1974 version of this engine, the SD-455 has heavier cylinder block with four bolt main bearings making a heavier but stronger cast block. The SD version is equipped with higher flow cylinder heads, forged push rods, and forged aluminum pistons. The prototype of the SD-455 was tested with functional hood scoops, a hot cam, and a different rocker- cam ratio than the engine that was offered to consumers. The marketed version had none functional hood scoops, a milder cam, and 1.5:1 rocker ratios with a low actual compression ratio of 7.9:1 however barely passed ever tightening emissions regulations but it still yielded 290 SAE net horse power measured at the crankshaft. The street ready engine can do the quarter mile in less than 15 seconds reaching 98 mph.
The body changed in 1974 with a “shovel-nose front end and wider slotted tail lights. The entry level engines are two in line six cylinder offers. The basic V8 is a 350 cu in (5.7 L) with a 400 cu in and depending on power options will produce 215 hp (160 kW) or 250 hp (190 kW). Next on the agenda is the 455 cu in (7.5 L) producing 215 hp (160 kW) or a 250 hp (190 kW) version as well the SD-455 was an option producing 290 hp (220 kW). The larger engines are stock equipment only on the Trans Am and Formula models in ’74.
The 1975 models featured a new wrap around rear window with a revised roof line and the turn signals were moved from the valance panel to the grill which distinguishes the ’75 from the previous model year. The Muncie four speed and the TurboHydramatic transmissions were no longer available in ’75. The 400 engine was the basic V8 for both 1975 and 1976 in the Trans Am. The 455 is the power option. With 7,100 units produced in ‘76 but ever tightening emission controls regulations meant that this was the last year for the “big cube birds”.