Trans Am Cars Second generation (1970–1981)
Picture Of Trans Am CarsA distinctive, slant-nose facelift occurred in 1977, redone somewhat in 1979. From 1977 to 1981, the Firebird used four square headlamps, while the Camaro continued to retain the two round headlights that had previously been shared by both Second Generation designs. Curb weights rose dramatically in the 1973 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 Cars weighed in at 3,850 lb (1,750 kg).
Picture Of Trans Am Cars
The 455 engine available in the second generation Firebird Trans Ams was arguably the last high-performance engine of the original muscle car generation. The 455 cu in (7.5 L) engine first made its appearance in 1971 as the 455-HO. In 1973 and 1974, a special version of the 455, called the SD-455, was offered. The SD-455 consisted of a strengthened cylinder block that included 4-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 1967 GTO Ram Air camshaft with 301/313 degrees of advertised duration, 0.407 inch net valve lift, and 76 degrees of valve overlap was specified for actual production engines in lieu of the significantly more aggressive Ram Air IV style cam that had originally been planned for the engine (initially rated at 310 hp (230 kW) with that cam), but proved incapable of meeting the tightening emissions standards of the era. This cam, combined with a low compression ratio of 8.4 (advertised) and 7.9:1 actual resulted in 290 SAE net horsepower. Production test cars yielded 1/4 mile times in the 14.5 second/98 MPH range in showroom tune - results consistent for a car with a curb weight of 3,850 pounds and the rated 290 SAE net horsepower figure some sources suggest was "under-rated," High Performance Pontiac magazine dyno-tested an SD and gave it 371 SAE net rating. During a 1972 strike, the Firebird (and the sister F-body Camaro) were nearly dropped. Pontiac offered the 455 for a few more years, but tightening restrictions on vehicle emissions guaranteed its demise. Thus, the 1976 Trans Am was the last of the "Big Cube Birds," with only 7,100 units produced with the 455 engine.
Picture Of Trans Am CarsThe 455 engine available in the second generation Firebird Trans Ams was arguably the last high-performance engine of the original muscle car generation. The 455 cu in (7.5 L) engine first made its appearance in 1971 as the 455-HO. In 1973 and 1974, a special version of the 455, called the SD-455, was offered. The SD-455 consisted of a strengthened cylinder block that included 4-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 1967 GTO Ram Air camshaft with 301/313 degrees of advertised duration, 0.407 inch net valve lift, and 76 degrees of valve overlap was specified for actual production engines in lieu of the significantly more aggressive Ram Air IV style cam that had originally been planned for the engine (initially rated at 310 hp (230 kW) with that cam), but proved incapable of meeting the tightening emissions standards of the era. This cam, combined with a low compression ratio of 8.4 (advertised) and 7.9:1 actual resulted in 290 SAE net horsepower. Production test cars yielded 1/4 mile times in the 14.5 second/98 MPH range in showroom tune - results consistent for a car with a curb weight of 3,850 pounds and the rated 290 SAE net horsepower figure some sources suggest was "under-rated," High Performance Pontiac magazine dyno-tested an SD and gave it 371 SAE net rating. During a 1972 strike, the Firebird (and the sister F-body Camaro) were nearly dropped. Pontiac offered the 455 for a few more years, but tightening restrictions on vehicle emissions guaranteed its demise. Thus, the 1976 Trans Am was the last of the "Big Cube Birds," with only 7,100 units produced with the 455 engine.
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