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1973 Buick Century Gran Sport Stage 1 455
Buick carried the Stage 1 into the new Colonnade era as the strongest factory engine available in the 1973 Century Gran Sport. The XS-code 455 used an 8.5:1 compression ratio, a four-barrel carburetor, dual exhaust, a dual-snorkel air cleaner, larger valves, and a performance camshaft. Its published rating was 270 horsepower SAE net with 390 lb-ft of torque.
The Stage 1 could be ordered with a floor-shifted four-speed or Turbo Hydra-Matic 400. Registry records account for 728 cars: 92 four-speeds and 636 automatics. Most were conventional hardtops, while 45 were Sun Coupes fitted with a manual or electric roof. The same records preserve unusually detailed paint, interior, assembly-plant, and option counts.
Every Century received front disc brakes and Buick's new full-perimeter frame. Gran Sport trim added a blacked-out grille, headlamp surrounds, and exterior details. The regular coupe and Sun Coupe belong on this page because the roof was an option within the same model and drivetrain identity, not a separate performance model.
A real Stage 1 should reconcile as a complete car. The fifth VIN character is V, the engine production code is XS, and the paint and trim fields should agree with the body plate and supporting paperwork. Badges, wheels, a black grille, or an installed 455 do not establish factory Stage 1 identity by themselves.