Working with Metals: Iron, Steel, Stainless

A prime example of where you might find a cast iron part is in the cylinder block or cylinder heads of older American automobiles. Tremendous horsepower and torque could be withstood by these iron parts with amazing reliability. Under heavy loads and stress the parts would retain their shapes, resulting in minimal wear. It is not uncommon to see cylinders that look almost new, even when the engine has over 100,000 miles.


What are the disadvantages of cast iron? The first and foremost reason that modern car builders shy away from iron is weight. Cast iron is very heavy and can weigh almost double that of the same component made out of a high-strength aluminum.


Another potential disadvantage of iron is brittleness. Since it resists deforming or bending, bad things happen when it finally does decide to move. That's right, it breaks like a potato chip. This is the big crux of metals. Sometimes a material's advantage in one situation can be a disadvantage in another. However, don't rule out cast iron as old technology. Many aftermarket and performance manufacturers still produce cast iron parts because of its extreme strength and durability.

The Steel Standard
Next in line are standard steels. Within this group is a dizzying amount of materials, but we will concentrate on the mild steels that you'll likely encounter in a standard restoration. Most steering and suspension parts are made from this type of steel. The reason it is used in such important load-bearing components is that it has some qualities that you can't find in iron, such as flexibility. When your teenaged son or daughter forgets about the curb in front of the mall because they are text messaging their friends on a new cell phone, mild steels could very well save their lives.


Even when mild steel is put under tremendous stress and is forced to deform, it just bends out of the way. Thus the wheels stay on the car, and the steering still works, albeit unlike new condition. In an accident the car can still be controlled because all of the steering and suspension parts are still attached to the vehicle, just bent out of shape. These steels are so resistant to breaking that they must be bent over and over before they finally crack and break in two. Other parts that see a wide array of mild steel are body panels, chassis and frames.