In 1973, Pontiac released a limited production engine known as the Super Duty 455 (SD 455). The engine was optional in ‘73 and ‘74 on both Formulas and Trans Am’s.
The SD-455 was a race bred engine that featured a special heavy duty block, forged pistons, four bolt main caps, a provision for dry sump oiling, round port heads that were reported to flow better than Chryslers’ Famed Hemi, "header" style exhaust manifolds, and an 800 cfm carb. Original SD-455 cars are valuable collectibles today.
Image above: The 2nd Generation Pontiac Trans Am Fender Extractor relieves the build up of high speed back-pressure aero drag on the firewall and "extracts" hot air from the engine compartment . And yes - that is the infamous T/A Shaker Scoop with the SD-455 decals.
All SD-455 equipped Firebirds have an "x" as the third digit in their VIN. The blocks are either stamped "XD" (w/auto trans.) or "ZJ" (w/man. trans.). The heads show casting number "16" and have a "6H" stamped on them. The part number is 485216. The carburetors carry part numbers 7043270 (‘73 w/auto trans.), 7043273 (‘73 w/man trans.), 7044270 (‘74 w/auto trans.), or 7044273 (‘74 w/man trans.). The exhaust manifolds are numbered 490802 for the right side and 492803 for the left. Formulas equipped with SD-455’s carried the Trans Am’s shaker hood instead of the Formula hood.
Trans Am 252 (180 w/ auto trans. 72 w/ man trans)
The Notorious 1973 SD 455 Trans Am (below).
Brewster Green SD 455 Shaker Scoop
Trans Am 943 (731 w/auto trans. 212 w/man trans)
In addition there were some SD-455 crate motors sold through dealers as factory 'Service Replacement' engines.
Image above: The infamous SD 455 Legend lives on in this Montreal trendy womens clothing store decoration titled "The Speeders Dusty days" is reminiscent of all of my favorite James Garner's - The Rockford Files episodes. You should have seen the look on the saleswomens' faces of me waiting on my lady while she was trying on her new cloths and me taking digital photos of this image next to their fitting room. Pontiac On!