One Of GM's Most Hated: Why Chevrolet's Iron Duke Engine Is So Maligned
General Motors is responsible for some of the greatest engines to ever see widespread use. The Chevy Small Block is considered by some to be the single best engine ever made due to the sheer availability of parts and its uncanny ability to make huge amounts of power without rapidly disassembling itself. Similarly, the famed LS has taken on a life of its own as seemingly every vehicle in existence has undergone an LS swap at the hands of an enterprising gearhead. There's also the 454 big block, which threw down unholy amounts of power in cars like the Chevelle and gave many pickups enough oomph to get the job done.
However, for every Small Block and LS, there are engines that don't quite reach the same level of fame, and in fact, are so maligned and sneered at that they fall to the same automotive dregs as cars like the Pontiac Aztek. One such engine is the GM 2.5-liter "Iron Duke." Even hearing that name is liable to make hardcore General Motors fans break out in a cold sweat and competing acolytes of both Ford and Chrysler start laughing uncontrollably. No matter the affiliation of any gearhead, the Iron Duke will garner a reaction.
A thin gruel of an engine
At least on the surface, the Iron Duke wasn't really that strange. It was a 2.5-liter four-cylinder that first showed up in Pontiacs in 1977. In its first iteration, it made 87 horsepower, which seems just north of a few lawnmowers, but it was fairly average for the late 1970s. Eventually, it would be featured in the engine bay of everything from the Chevy Citation, to Jeeps, to the Grumman LLV mail truck you are likely familiar with. It even had a cameo appearance in some AMCs like the Concord. The Pontiac Fiero and Chevy Camaro even joined in on the four-cylinder fun.
The Iron Duke is hated to this day not because of what it was, but because of what it wasn't: an even remotely interesting engine. It wasn't fast, didn't sound particularly exciting, and didn't excel in any possible metric. "Vanilla" wouldn't describe it because vanilla has a perceptible flavor. The Iron Duke is more like a thin gruel. It will keep you alive, but it won't be an enjoyable experience. It's certainly possible to have fun with under 100 horsepower, but when the car you are driving is a Chevy Citation or a Camaro that can barely reach the speed limit, the capacity for fun is pretty limited.
Nothing to write home about
The Iron Duke wasn't even unreliable or plagued with issues that weren't already inherent with weak carbureted engines. According to many reports from people who owned one, it was fairly reliable, hence the use in mail trucks which will likely continue until after the heat-death of the universe. In some ways, the Iron Duke is like an old dryer you don't like: it's loud, ugly, and fiddly to use, but it keeps on running and it dries your clothes just fine. You also hope it will give up the ghost one day so you have an excuse to get a new one.
According to Driving Line, the most horsepower the Iron Duke would ever make was 110 before finally going the way of the Dodo in 1992. The Iron Duke was exactly "fine" as it was dependable and reasonably fuel efficient. MotorWeek, in its review of the 1984 Fiero with an Iron Duke, described it as "adequate." But when you're driving the latest Camaro or Fiero, you probably want something more than just "fine." The Iron Duke failed where it mattered most, getting customers to care.