The Iron Duke Pontiac engine VIN code A (also called the 2500, 151, Pontiac 2.5, and Tech IV, though the decal on the air filter assemblies actually reads "4 Tech") is a 2.5 L (150.8 cu in) I4 piston engine. All Iron Dukes were built by Pontiac beginning in 1977 and ending in 1993. After this time, the GM 2.2 L OHV 4-cylinder replaced it across the entire lineup of vehicles that offered it. This engine is not to be confused with the Chevrolet 153.