This article is about the automobile engine. For the steam locomotive, see GWR Iron Duke Class.
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Reciprocating internal combustion engine
Iron Duke
Overview
Manufacturer
General Motors
Also called
Tech IV (1982-1990)
Production
1977–1993
Layout
Configuration
Straight-four
Displacement
150.8 cu in (2.5 L)
Cylinder bore
4 in (101.6 mm)
Piston stroke
3 in (76.2 mm)
Cylinder block material
Cast iron
Cylinder head material
Cast iron
Valvetrain
OHV 2 valves x cyl.
Compression ratio
8.25:1 (1977–1983) 9.0:1 (1984–1993)
RPM range
Max. engine speed
5000 rpm
Combustion
Fuel system
Carburetor Throttle-body fuel injection
Fuel type
Gasoline
Oil system
Wet sump
Cooling system
Water-cooled
Output
Power output
85–110 hp (63–82 kW)
Specific power
34.4 hp (25.7 kW)-44.5 hp (33.2 kW) per liter
Torque output
123–135 lb⋅ft (167–183 N⋅m)
Dimensions
Dry weight
375 lb (170 kg)[1]: 3
Chronology
Predecessor
GM 2300 engine
Successor
GM 122 engine
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 until 1993. Originally developed as Pontiac's new economy car engine, it was used in a wide variety of vehicles across GM's lineup in the 1980s as well as supplied to American Motors Corporation (AMC). The engine was engineered for fuel efficiency, smooth operation, and long life, not for performance.[2] Total Duke engine production is estimated to be between 3.8 and 4.2 million units.[3]
^Sawruk, John M. (26–30 September 1977). Pontiac's New 2.5 Litre 4 Cylinder Engine(PDF). Society of Automotive Engineers: Passenger Car Meeting. Detroit. Archived from the original (PDF) on 5 February 2018. Retrieved 17 August 2019.
^Hunting, Benjamin (May 26, 2021). "GM's Unkillable Iron Duke 4-Cylinder Engine Powered Dozens Of Trucks, Cars, and SUVs For Decades". DrivingLine. Retrieved January 20, 2023.
^Appel, Tom (September 12, 2018). "What Was The Iron Duke?". The Daily Drive by Consumer Guide. Retrieved January 20, 2023.
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