What is a Trans Am SD-455?

By Mike Sullivan · 1 min read · Updated Jun 2026

Quick Answer

The SD-455 is the Super Duty 455 V8 offered in the 1973-1974 Pontiac Firebird Trans Am, a race-bred big-block that was the last true muscle engine of the era. It is rare and powerful, which makes a documented SD-455 Trans Am the blue-chip second-generation Firebird.

The SD-455 is the high-water mark of Firebird performance.

Why it is special

The Super Duty 455 had a strengthened block, special heads, and serious output at a time when muscle was dying off across the industry. Production was small over 1973 and 1974.

Buyer's note

Demand PHS (Pontiac Historic Services) documentation. The SD-455 is among the most valuable and most faked Pontiac engines, so verify the codes before paying the premium.