The Iron Duke engine: an American interpretation of a European staple.
The Americans have a different approach to engines than do Europeans. First, they hold the view that bigger is better which means that for many decades the smallest engines were usually 6-cylinder units. 8-cylinder units were considered standard. When the oil crises of the 70s struck, the main US manufacturers were not so experienced with the 4 cylinder devices that were needed to cope.
That meant that when they arrived their small engines weren’t even all that small. GM’s offering in the smaller compact class was the Iron Duke, a 2.5 litre pushrod engine with power outputs of between 85 hp and 110 hp. Second, Americans had a preference to build engines for durability rather than refinement (which makes sense in the US context). So, when it came time for GM to develop a general purpose engine, it was not in a good position to make the small-capacity, 4-cylinder format work so very nicely.
The Iron Duke was a mainstay of GM’s 4-cylinder cars for nearly decades, adding that precious touch of roughness to all of them. The Duke was sold from 1977 to 1992 in the following cars: the 1977 Pontiac Astre, 1977-1979 Pontiac Phoenix, 1977–1980 Pontiac Sunbird, 1978–1980 Chevrolet Monza and Oldsmobile Starfire,1980–1984 Oldsmobile Omega, Pontiac Phoenix, 1980–1985 Buick Skylark, Chevrolet Citation,1982–1984 Chevrolet Camaro, Pontiac Firebird,1982–1989 Chevrolet Celebrity,1982–1991 Pontiac 6000,1982–1992 Buick Century, Oldsmobile Cutlass Ciera,1984–1988 Pontiac Fiero,1985–1987 Chevrolet S-10 Blazer, GMC S-15 Jimmy,1985–1993 Chevrolet S-10, GMC S-15/Sonoma,1985–1990 Chevrolet Astro, GMC Safari,1985–1987 Buick Somerset,1985–1991 Pontiac Grand Am, Oldsmobile Cutlass Calais,1986–1991 Buick Skylark,1990–1992 Chevrolet Lumina.
Now I have typed all that out I realise that the Iron Duke was closely related to some of GM’s least appealing cars. With the possible exception of the Chevrolet Lumina and the Skylark, all of those cars were below average. The Iron Duke, in its later days, was termed the Low-Tech IV by Car and Driver which was their way of saying it had outstayed its welcome by about the middle 80s.
Criticisms of the engine are centred on its roughness at the higher end of the operating range and its old-fashioned iron-construction, along with the resultant weight. But it was reliable and simple enough to repair. Questions for an engineer to answer relate to why it took GM USA 2.5 litres of capacity to produce the same or similar power outputs Opel was achieving with its 4-cylinder engines in Europe. And indeed, if Opel had been working on 4 cylinder engines for decades longer than GM USA, why was there a need for the Iron Duke at all? Was it a question of “not engineered here”? Or a question of not built to the right price?
The most inappropriate deployment of the Iron Duke was in the 1983-1988 Pontiac Fiero. What ought to have been under the bonnet of this handily-sized sports car was a small V6. But instead the accountants decreed the Iron Duke would do service too. What was just about appropriate for the commodity-car Citations and Phoenixes in GM’s stable really did not belong in a sports car aimed at enthusiasts.
This was yet another example of GM’s mid-80s death-wish. While being charitable to the Iron Duke on the basis that it ran quite well and did what little was asked of it, it was also an engine that added an important extra bit of dissatisfaction to the experience of owning too many of GM’s cars. Given the enormous production volumes involved and the necessity of having a good 4-cylinder, the least GM could have done was to make the engine less dreary to listen to.
That could have been done not only by the European methods of adding complexity and fragility but by throwing some brain-power in the form of engineering development. In typical GM fashion they didn’t bother and, possibly in so doing lost the small car market to Honda and Toyota who understood 4-cylinder engines better than almost anybody.
I am indebted to the Jalopnik website for some of the insights here. In particular, Murilee Martin, who penned the reference article, has to be commended.