The GM “Iron Duke” engine was built by the Pontiac Motor Division of General Motors from 1977 to 1993. It’s original purpose was to be Pontiac’s new economy car engine, but it was later adapted to be used in many more vehicles.
GM began to sell the engine to AMC starting in the 1980 model year. It was used in the Spirit, Concord, and Eagle model vehicles. It was also used in select Jeep CJ models. It was used in three Jeep models:
- 1981-1983 CJ-8
- 1980-1983 CJ-7
- 1980-1983 CJ-5
Oil Types and Capacities
|Viscosity||Above 40°F: 10W-30, 20W-30, 10W-40, 30W, 40W|
Above 0°F: 10W-30, 10W-40, 20W
Below 0°F: 5W-20, 5W-30, 10W*
|Capacity||3 qts (2.8L)|
|Oil Filter||WIX 51040|
|1978||85hp @ 4400rpm||123lb-ft @ 2800rpm|
|1980||90hp @ 4000rpm||134lb-ft @ 2400rpm|
|1981||84hp @ 4000rpm||125lb-ft @ 2400rpm|
Chipped Timing Tooth
The most common failure point of the 2.5L Iron Duke is the timing gear, which is known to chip a tooth around 80,000 miles. The replacement is laborious and requires the replacement gear to be heat-fitted onto the shaft.