Fortunately for performance buffs, Pontiac's Special Projects had one more trick up its collective sleeve before the catalytic converter came in and finished off the era. In the spring of 1972, Pontiac held a press conference at its '73 long-lead media event announcing the release of a limited-production, purpose-built race engine that was detuned somewhat for street operation, yet would give privateer racers a very solid basis for competition use. Known internally by such nicknames as "Hemi Hunter" and "Rat Eater," it was officially dubbed the 455 Super-Duty, calling to mind the legendary Pontiac factory racing program of 1960-1963. They even had cars at the event capable of low 13s at 105 mph.
To say that the enthusiast press was excited was the understatement of the year. In an age of tape-stripe performance and phony mag wheels, the 455 Super-Duty was like a bucket of cold water over the head-it was the real deal in a sea of poseurs.
Pontiac engineers had addressed the weak points of the Pontiac V-8 engine and corrected them. The block featured four-bolt mains, of course, and was reinforced with lifter bracing to prevent splitting down the middle. Forged rods and pistons replaced the weaker cast units used for years, and the crankshaft, while cast, featured rolled fillets for improved strength and crack resistance. Even the oiling system's shortcomings had been addressed, and there were provisions cast in the back of the block for a dry-sump to be added. As we said, it was a real race engine.
Like the short-block, the top-end received some critical improvements from the 455 H.O. The round-port heads were enlarged for a consistent cross-sectional area, this change coming from data acquired from the 303 Trans Am and 366 NASCAR programs. A cast-iron, big-port intake manifold was topped off with a special 800-cfm Quadrajet, and exhaust gases were expelled through high-capacity cast-iron exhaust manifolds.
After looking for the best combination of performance and emissions, a special version of the 301/313-degree duration Ram Air III camshaft (stamp "K") was eventually settled on, this one using a smaller distributor gear to coincide with the larger gear used on the distributor to reduce spark scatter.
The end result was an engine rated at 290 SAE net horsepower at 4,000 rpm and 395 lb-ft of torque at 3,600. While that figure might not sound all that impressive by today's standards, it was de-emphasized somewhat and rated at a lower-than-peak rpm level. Though it only had an 8.4:1 compression ratio, a myriad of emission control devices, and a fairly mild cam, it was still one of the most powerful engines of the classic musclecar era.
Timing is everything though, and the time wasn't right for the SD. With the cost of recertifying all of Pontiac's V-8s after the EPA found timers on the EGR valves that would render them inoperative after the duration of an emissions test, Pontiac limited the availability of the engine to the Firebird Formulas and Trans Ams. The widespread availability of the 455 Super-Duty in LeMans, GTO, Grand Prix, and Grand Am models was promised in early sales brochures, but never actually happened.
As it turned out, the '73 GTO was offered with the garden-variety 400 and 455 D-port powerplants, and production plummeted to 4,806 units. The aforementioned timing problems, as well as the internal competition from the new Grand Am, further reduced demand for the GTO.