All about the 1970-76 Firebird and Trans Am

[Trans Am Guru]

The second generation debut for the 1970 model year was delayed until February 26, 1970, because of tooling and engineering problems; thus, its popular designation as a 1970½ model, while leftover 1969s were listed in early Pontiac literature without a model-year identification. This generation of Firebirds were available in coupe form only; after the 1969 model year, convertibles were not available until 1991.

Models
Firebird Base
Firebird Esprit
Firebird Formula
Firebird Trans-Am

Special versions and appearance packages
Formula Appearance Package "W50" (1976–1981)
Black-and-Gold Trans Am Pontiac 50th Anniversary Limited Edition (1976)
Black-and-Gold Trans Am Special Edition (1977–1978, 1980–1981)
Sky Bird Esprit Appearance Package "W60" (1977–1978)
Gold Trans Am Special Edition "Y88" (1978)
Red Bird Esprit Appearance Package "W68" (1978–1979)
Black Trans Am Special Edition "Y84" (1979)
Trans Am 10th Anniversary Edition (1979)
Yellow Bird Esprit Appearance Package "W73" (1980)
Trans Am Turbo Indy Pace Car Edition (1980)
Trans Am Turbo NASCAR Pace Car Edition (1981)
Macho Trans-Am (a package offered by the Mecham Pontiac dealership in Glendale, AZ)

Replacing the "Coke bottle" styling was a more "swoopy" body style, while still retaining some traditional elements. The top of the rear window line going almost straight down to the lip of the trunk lid, a look that was to epitomize F-body styling for the longest period during the Firebird's lifetime. The new design was initially characterized with a large C-pillar, until 1975 when the rear window was enlarged.

1970
There were two Ram Air 400 cu in (6.6 L) engines for 1970: the 335 hp (250 kW) L74 Ram Air III (366 hp (273 kW) in GTO) and the 345 hp (257 kW) LS1 Ram Air IV (370 hp (280 kW) in GTO) that were carried over from 1969. The difference between the GTO and Firebird engines was that the secondary carburetor's throttle linkage had a restrictor which prevented the rear barrels from opening completely, adjusting the linkage could allow full carburetor operation resulting in identical engine performance.

For the 1970 and 1971 model years, all Firebirds equipped with radios had the antennas mounted "in-glass" in the windshield.

1971
The Pontiac 455 cu in (7.5 L) engine first became available in the second generation Firebird in 1971. The 455 engine was available in the L75 325 hp (242 kW) version and the LS5 335 hp HO version, which was the standard, and only engine option, for the Trans Am. The HO engine also included Ram Air IV.

1972
During a 1972 strike, the Firebird (and the similar F-body Camaro) were nearly dropped. Again the 455HO was the only engine available for the Trans Am. Starting in 1972, and continuing until 1977, the Firebird was only produced at the Norwood, Ohio, facility.

1973
Actual production cars yielded 1/4 mile results in the high 14 to 15.0 second/98 MPH range (sources: Motor Trend Magazine, July '73 and Roger Huntington's book, American Supercar) – results that are consistent with a 3,850 pound car (plus driver) and the engine equipped with a 4-barrel Rochester Quadrajet carburetor rated at a maximum power of 290 bhp (294 PS; 216 kW) at 4000 rpm and a maximum torque of 395 lb⋅ft (536 N⋅m) at 3600 rpm figure.[16] An original rating of 310 bhp (314 PS; 231 kW) SAE net had been assigned to the SD-455, though that rating was based on the emissions non-compliant "pre-production" engines, as mentioned above. That rating appeared in published 1973 model year Pontiac literature, which had been printed prior to the "pre-production" engines "barely passing" emissions testing, and the last minute switch to what became the production engine. The 1974 model year production literature listed the specifications of the production engine (290 SAE net horsepower).

In 1973 and 1974, a special version of the 455, called the Super Duty 455 (SD-455), was offered. The SD-455 consisted of a strengthened cylinder block that included four-bolt main bearings and added material in various locations for improved strength. Original plans called for a forged crankshaft, although actual production SD455s received nodular iron crankshafts with minor enhancements. Forged rods and forged aluminum pistons were specified, as were unique high-flow cylinder heads.

A production line stock SD455 produced 253 rear wheel HP on a chassis dyno, as reported by High Performance Pontiac magazine (January, 2007). This is also consistent with the 290 SAE net horsepower factory rating (as measured at the crankshaft). Skip McCully verified that no production SD455s released to the public were fitted with the 480737 cam. When asked about the compromises for the production SD455 engine, McCully responded, "Compression, camshaft, jetting, and vacuum advance." He followed by stating that he would have preferred a compression ratio of 10.25:1, a camshaft with 041 valve timing, slightly richer carburetor jetting, and as much vacuum advance as the engine would tolerate. However, that proved to be impossible due to the emissions regulations of the era.

The 480737 code cam (identical grind to the RAIV "041" cam) was originally specified for the SD455 engine and was fitted into the "pre-production" test cars (source: former Pontiac special projects engineer McCully), one of which was tested by both Hot Rod and Car and Driver magazines. However, actual production cars were fitted with the milder 493323 cam and 1.5:1 rocker ratios, due to the ever-tightening emissions standards of the era. This cam and rocker combination, combined with a low compression ratio of 8.4:1 advertised (7.9:1 actual) yielded 290 SAE net horsepower. Production SD455 cars did not have functional hood scoops, while the "pre-production" test cars did.

Pontiac offered the 455 through the 1976 model year, but the engine could not meet tightening restrictions on vehicle emissions. A total of 7,100 were produced with the 455 engine.

1974
Curb weights rose dramatically in the 1974 model year due to the implementation of 5 mph (8.0 km/h) telescoping bumpers and various other crash and safety related structural enhancements; SD455 Trans Ams weighed in at 3,850 lb (1,750 kg) in their first year of production (1974 model year; actually 1973).

The 1974 models featured a redesigned "shovel-nose" front end and new wide "slotted" taillights. In 1974, Pontiac offered two base engines for the Firebird: a 100 hp (75 kW) 250 cu in (4.1 L) inline-6 and a 155 hp (116 kW) 350 cu in (5.7 L) V8. Available were 175 to 225 hp (130 to 168 kW) 400 cu in (6.6 L) V8 engines, as well as the 455 cu in (7.5 L) produced 215 or 250 hp (160 or 186 kW), while the SD-455 produced 290 hp (220 kW). The 400, 455, and SD-455 engines were offered in the Trans Am and Formula models during 1974.

A 1974 Firebird was driven by Jim Rockford in the pilot movie and the first season (1974-1975) of The Rockford Files, and every following season, Rockford would change to the next model year. However, in the sixth season (1979-1980), Rockford continued to drive the 1978 Firebird from season 5, as James Garner disliked the 1979 model's restyled front end. The cars in the show were badged as lower-tier Esprit models, but in reality were Formulas with the twin-scoop hood replaced with a scoopless one. Another hint was the twin exhausts and rear anti-roll bars that were not used on Esprit.

1975
The 1975 models featured a new wraparound rear window with a revised roofline and the turn signals were moved up from the valance panel to the grills which distinguished it from the previous year model. The Super Duty engine, Muncie 4-speed, and TurboHydramatic 400 automatic were no longer available in 1975. Due to the use of catalytic converters starting in 1975, the THM 400 would not fit alongside the catalytic converter underneath the vehicle. The smaller TurboHydramatic 350 automatic was deemed enough. The 400 was standard in the Trans Am and the 455 was optional for both 1975 and 1976 models.

1976
Pontiac celebrated its 50th anniversary year in 1976. To commemorate this event, Pontiac unveiled a special Trans Am option at the 1976 Chicago Auto Show. Painted in black with gold accents, this was the first "anniversary" Trans Am package and the first production black and gold special edition. A removable T-top developed by Hurst was optional, but proved problematic.