The Pontiac Firebird Trans Am SD-455 is a special variant of the second-generation Firebird muscle car.
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. 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.
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.
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. Overlooked however, is a June 1974 test of a newly delivered, privately owned SD-455 Trans Am. This appeared in Super Stock and Drag Illustrated. With an unmodified car and a test weight of 4,010 lbs the testers clocked 14.25 seconds at 101 mph. The car had automatic and A/C. Also, the factory rating of 290 hp was listed at 4,400 rpm while the factory tachometer has a 5,750 rpm redline.
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.
Asphalt Street Storm
The Pontiac Firebird was part of the original car roster but would not be available until the global launch of Street Storm in June 2017. It was first launched in a 3 day Champions Clash for 2017's Fourth of July. The car was given out as a reward for the top 10 players.