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Despite the gloom of a disastrous strike at the Norwood, Ohio assembly plant, the oil shock of
1973 and a looming auto insurance crisis Pontiac forged ahead with a rather daring plan to introduce a new version
of the 455, prefixed the 'Super Duty," for the 1973 Firebird, at a time
when big-displacement performance engines were becoming a rare sight in the
showroom. The Firebird V-8's displacement to 455 cu in. Two 455s
were planned for the Formula and Trans Am, and both were rated in gross and net
horsepower as the SAE net output formula gradually replaced the unladed gross
ratings that GM used previously. The
“Cooking” 455 was rated at 325-gross/255 net bhp, while the 455 HO
was good for an additional 60 bhp net!
Designed for the new realities of low-octane fuel and emission
controls, the engine was announced at 310 bhp, but was down rated to 290 when it
entered production.  That was still power enough to get so-equipped Trans Am’s
to 60 mph in less than 5.5 seconds. And, they would likely continue to perform
for years to come, thanks to the SD's robust construction, which included 4-bolt
main bearings with a provision for dry-sump lubrication just in case someone
wanted to take it racing, of course. Other tasty tidbits ranged from forged
pistons and connecting rods to large-port heads and a more generous Quadra jet
carburetor. The engine helped Pontiac retain the Firebird's position at the
upper end of the pony car performance spectrum.
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