The Iron Duke engine (also called 151, 2500, Pontiac 2.5, and Tech IV) is a 151 cu in (2.5 L) Straight-4 piston engine built by the Pontiac Motor Division of General Motors from 1977 to 1993. Thereafter GM's 2.2 L OHV 4-cylinder replaced it across the entire lineup of vehicles that offered it. Although its original purpose was to serve as Pontiac's new economy car engine, it was later adapted for use in a wide variety of applications across GM's lineup in the 1980s.