Much has changed in the automotive industry since the beginning of the 20th century. Traditionally, the material trusted under the hood for engine blocks was iron. In fact, some brands like Dodge and Ram still use iron engine blocks in some vehicles. However, there has been a gradual move toward aluminum, dethroning what had been the go-to standard.
It’s not that aluminum is some new metal that manufacturers just recently started experimenting with; on the contrary, in terms of its use in engines, there have been several examples dating back to the 1960s. For example, Chevy’s RPO ZL1 – a 427 with an aluminum alloy block — was an early adopter. Others included Oldsmobile, Chrysler, and Plymouth, to name a few, during the same decade. The Buick 3.5-liter V8 (later sold to Rover) also featured an aluminum block, and was one of the smallest displacement production V8s ever made.
The big reason automakers were looking into aluminum so intently during the ’60s is that — although earlier versions of the metal didn’t hold up well against the brute strength of iron — engineers had made strides in the metallurgy process over in Europe. Before muscle cars rose to prominence, U.S. automakers wanted to be competitive in the compact market, where weight was a major consideration. And the weight advantage of aluminum over iron was substantial — iron is nearly three times the density of pure aluminum, significantly tipping the scales.
Weight is still a driving factor for aluminum blocks, as drivers expect greater fuel economy and the Environmental Protection Agency (EPA) has tightened emissions standards. One way to reduce fuel consumption and lower a vehicle’s CO2 output is to reduce its weight, requiring less energy from the engine.
Iron still offers some advantages
The robust density of iron not only makes for a durable block, even in industrial applications, but it also helps muffle mechanical noise under the hood. Essentially, sound waves can’t travel through denser material as easily, reducing transmission.
In addition, in high-performance applications, an iron block is much more forgiving if pushed too hard, such as during engine failure. Put an aluminum block through the same torture and it can deform, or require significant repairs following a mishap. One of the ways automakers are essentially getting some benefits from both metals is including iron cylinder liners within aluminum engine blocks. Wear within the cylinder can be mitigated with this addition. Without incorporating these cast iron components, the aluminum would degrade more quickly, leading to a shortened lifespan.
Designs under the hood continue to evolve as engineers dream up ways to potentially transform the automotive industry. Unfortunately, unlike some of the improvements made in the manufacture of aluminum engine components, not all ideas result in success. Take, for instance, the idea of an internal combustion engine that didn’t need oil, had no piston rings, and used only a very small gap between the piston and cylinder wall. Although amazing on paper, the concept proved exceedingly difficult to machine.
