This is a 1974 Pontiac Firebird Trans Am SD-455, it’s one of the last true muscle cars from the golden age, before emissions restrictions and the 1973 Oil Crisis almost killed off the genre entirely.
The SD-455 engine option got the buyer the Super Duty 455 cubic inch V8 that was good for 290 bhp and 395 lb ft of torque. It could be ordered with either a 4-speed manual or a 3-speed automatic, and it was one of the quickest American production cars of its time.
Fast Facts: A 1974 Pontiac Firebird Trans Am SD-455
- The 1974 Pontiac Firebird Trans Am SD-455 was among the last high-performance American muscle cars of its era. Its 455 cubic inch (7.5 liter) Super Duty V8 produced 290 bhp and 395 lb ft of torque, making it one of the quickest American production cars available despite tightening emissions regulations.
- Developed under Pontiac engineer Herb Adams, the SD-455 had a reinforced engine block, forged connecting rods and pistons, and high-flow cylinder heads. Originally rated at 310 bhp, its output was reduced to 290 bhp following camshaft revisions for emission purposes. Emissions certification problems delayed its introduction until partway through the 1973 model year.
- The SD-455 was offered with either a 4-speed manual or 3-speed automatic transmission. Pontiac built just 1,296 Super Duty Firebirds across 1973 and 1974, including 1,195 Trans Ams. The engine was discontinued for 1975 as stricter emissions standards, rising fuel costs, and changing buyer priorities affected the muscle car market.
- The 1974 Trans Am shown here was delivered new to Dave Waite Pontiac in Indianapolis, finished in Buccaneer Red with an SD-455 V8, TH400 automatic, and Safe-T-Track differential. It keeps numerous period features, has approximately 38,000 miles showing, and it’s offered for sale out of Arizona with its original build sheet and supporting documentation.
History Speedrun: Pontiac Firebird Trans Am SD-455
Pontiac introduced the Trans Am in 1969, initially it was an option package on the Firebird, and it was popular enough to get moved along to the second-gen body in 1970. By 1972 sales had fallen to 1,286 cars, in a year when a 174-day strike at GM’s Norwood assembly plant disrupted production. Compression ratios across Detroit were dropping to suit 91 octane fuel, power was dropping as a result, and this was before the 1973 Oil Crisis came along and ruined what was left of the muscle car’s golden age.
Special Projects engineer Herb Adams led the Super Duty 455 program with Skip McCully, Tom Nell, and Jeff Young. The plan was to build an engine that would meet emissions/compression ratio restrictions while still offering the horsepower and torque that big block V8 buyers had become accustomed to. Image courtesy of General Motors.
Special Projects engineer Herb Adams led the Super Duty 455 program with Skip McCully, Tom Nell, and Jeff Young. The plan was to build an engine that would meet emissions/compression ratio restrictions while still offering the horsepower and torque that big block V8 buyers had become accustomed to.
The engine they came up with was a 455 cubic inch (7.5 liter) V8 with a reinforced block, forged connecting rods and pistons, and new high-flow cylinder heads – its name revived the “Super Duty” label from Pontiac’s racing engines of the early 1960s.
Pontiac presented it in June of 1972 at its 1973 press preview, held at GM’s Milford Proving Ground, with a rating of 310 bhp at 4,000 rpm and 390 lb ft of torque at 3,600 rpm. The plan was to offer it in the Pontiac LeMans, GTO, Grand Am, and Grand Prix, as well as the Firebird.
A Year Of Delays
Ultimately, only the Firebird got the Super Duty 455, and even then not until later in the 1973 model year. The preview engine used camshaft timing taken from the Ram Air IV, with 308º of intake duration and 320º of exhaust. According to McCully, it met the federal 1973 emissions standard but not the stricter internal standard GM had set for itself.
Pontiac substituted a milder camshaft with 301º and 313º of duration, and on November 3, 1972 it published new ratings of 290 bhp at 4,000 rpm and 395 lb ft of torque. By way of a comparison, the Trans Am’s regular 455 V8 option was rated at 250 bhp.
The EPA (Environmental Protection Agency) determined that all of Pontiac’s 1973 V8s used a device that overrode EGR (exhaust gas recirculation) under certain conditions. It was a catastrophe, and the division had to re-certify every single one of them by mid-March 1973.
This is a 1974 Pontiac Firebird Trans Am SD-455, it’s one of the last true muscle cars from the golden age, before emissions restrictions and the 1973 Oil Crisis almost killed off the genre entirely.
Pontiac General Manager Martin Caserio considered canceling the Super Duty program entirely at this point. He eventually decided to keep it because Pontiac already had parts on hand and open purchase agreements with suppliers, his only condition was that it went into the Firebird alone.
The SD-455 Engine + Chassis
The SD-455 block had thicker bulkheads, four-bolt main bearing caps, and extra material in the camshaft and lifter area, along with provision for dry-sump lubrication. Pontiac used a cast iron crankshaft in place of a forging and pressure-rolled the journal fillets, a treatment that compresses the metal at the base of each journal so cracks are less likely to start.
The heads had round exhaust ports, compression was 8.4:1 for 91 octane fuel, and induction was by a single Rochester Quadrajet four-barrel. The bore x stroke was 4.15 x 4.21 inches.
The Trans Am chassis was a unit construction body with a bolt-on front subframe carrying unequal-length control arms and coil springs. The live rear axle rode on leaf springs, and there were anti-roll bars at both ends. Brakes were 11-inch vented discs in front and 9.5-inch drums in the rear with power assistance, and the steering was variable-ratio recirculating-ball, power assisted.
Buyers chose from a 4-speed manual or the 3-speed Turbo Hydra-Matic 400. In 1973 the SD-455 engine added $521 USD ($3,960 USD in 2026 dollars) to the Trans Am’s $4,204 USD ($31,940 USD in 2026 dollars) base price.
Performance Figures + Production Numbers
A pre-production automatic Trans Am built to the 310 bhp specification ran the quarter mile in 13.751 seconds at 103.56 mph at Orange County International Raceway on February the 7th, 1973 in a Car and Driver magazine test. It reached 60 mph in 5.4 seconds. A Hot Rod magazine test later the same year recorded 13.54 seconds at 104.29 mph, very much in the same ballpark as the first.
The SD-455 engine option got the buyer the Super Duty 455 cubic inch V8 that was good for 290 bhp and 395 lb ft of torque. It could be ordered with either a 4-speed manual or a 3-speed automatic, and it was one of the quickest American production cars of its time.
Pontiac built 252 Trans Ams and 43 Formulas with the SD-455 engine in what remained of the 1973 model year. Of the Trans Ams, 180 were automatics and 72 had the 4-speed. The 1974 cars got the Firebird’s redesigned front end, and production rose to 943 Trans Ams (731 automatics and 212 4-speeds) and 58 Formulas.
That made 1,296 Super Duty Firebirds over two model years, 1,195 of them Trans Ams. Total Trans Am production was 4,802 in 1973 and 10,255 in 1974, so the engine only went into about 5% of Trans Ams the first year and 9% the second.
It’s worth noting the fact that the 1973 Oil Crisis landed in October of 1973 and ran well into 1974, causing oil prices to rise as much as 400%, gasoline prices were similarly affected. This made cars like the SD-455 seem like a rather foolhardy idea, and it was almost certainly the main reason for the poor sales of the engine option.
Pontiac canceled the SD-455 for 1975, when emissions standards tightened again and fuel economy took priority. Surviving original examples now sell for well into the six figures.
The 1974 Pontiac Firebird Trans Am SD-455 Shown Here
This is an original 1974 Pontiac Firebird Trans Am SD-455, it was delivered new to Dave Waite Pontiac in Indianapolis, Indiana. It was finished in Buccaneer Red and factory-equipped with the 455 cubic inch (7.5 liter) Super Duty V8, paired with a TH400 3-speed automatic transmission and a Safe-T-Track limited-slip differential with 3.08:1 gearing.
The engine has a Rochester Quadrajet four-barrel carburetor and was factory-rated at 290 bhp and 395 lb ft of torque. The exterior keeps its Buccaneer Red finish and features a Shaker hood, Trans Am hood decal, front air dam, fender air extractors, rear spoiler, and black-finished bumpers.
It rides on 15-inch chrome American Racing wheels fitted with Goodyear Eagle GTII tires. It also has power steering, power-assisted front disc brakes, rear drum brakes, and a dual exhaust system with chambered mufflers. Inside, the cabin is upholstered in black cloth and vinyl, with a full-length center console, a Formula steering wheel, and an engine-turned dashboard.
This is an original 1974 Pontiac Firebird Trans Am SD-455, it was delivered new to Dave Waite Pontiac in Indianapolis, Indiana. It was finished in Buccaneer Red and factory-equipped with the 455 cubic inch (7.5 liter) Super Duty V8, paired with a TH400 3-speed automatic transmission and a Safe-T-Track limited-slip differential with 3.08:1 gearing.
Factory equipment includes air conditioning, a tilt steering column, an AM/FM radio, an 8-track player, and a rear window defogger. Instrumentation includes a 160 mph speedometer, tachometer, analog clock, and supplementary gauges. The five-digit odometer currently shows ~38,000 miles, with only a handful added since the seller bought the car in 2022.
It’s now being offered for sale out of Sedona, Arizona with the original build sheet documenting its factory specification and initial dealership delivery, a reproduction window sticker, owner’s manuals, and a clean Arizona title in the seller’s name. If you’d like to read more about it or register to bid you can visit the listing here.
Images courtesy of Pontiac + Bring a Trailer
Articles that Ben Branch has written have been covered on CNN, Popular Mechanics, Smithsonian Magazine, Road & Track Magazine, the official Pinterest blog, the official eBay Motors blog, BuzzFeed, Autoweek Magazine, Wired Magazine, Autoblog, Gear Patrol, Jalopnik, The Verge, and many more.
Silodrome was founded by Ben back in 2010, in the years since the site has grown to become a world leader in the alternative and vintage motoring sector, with well over a million monthly readers from around the world and many hundreds of thousands of followers on social media.
