Pros and Cons of Iron and Aluminum Engine Blocks

Pros and Cons of Iron and Aluminum Engine Blocks

August 9, 2021

Iron or aluminum? When it comes to engine blocks, that is the question. For years, engine blocks on most cars were made with cast iron. But more recently, aluminum and aluminum alloy metals have become a more popular choice when it comes to engine block composition.

When you look at iron vs. aluminum engine blocks, you’ll realize they both have their advantages and drawbacks. How you intend to use your engine will likely inform which material you elect to use. Let’s take a closer look at iron vs. aluminum engine blocks.

Iron engine blocks

Iron engine blocks were the standard material composition for many years, and it’s easy to see why.


  • Strength: Cast iron blocks are typically stronger than aluminum engine blocks, and they can stand up to higher internal pressures.
  • Power: On balance, iron engine blocks are going to produce more horsepower than aluminum engine blocks.
  • Easier to customize: Certain cast iron engine blocks can be upgraded without having to alter the engine’s internal components.
  • Cost: Typically, iron engine blocks are significantly cheaper than aluminum engine blocks.


  • Weight: Iron engine blocks weigh more than aluminum engine blocks, which hurts fuel economy and performance.
  • Easier to replace than to repair: Because iron engine blocks cost less, if one of the cylinders or components needs to be repaired, that can cost nearly as much as a replacement block.
  • Rust: Iron is prone to rusting, which can be a factor when considering the stress and pressure the engine block is going to be put through.

Aluminum engine blocks

Most new vehicles use aluminum engine blocks, as they are a viable alternative to cast iron.


  • Lighter: Aluminum engine blocks are lighter than iron blocks, and this not only helps with gas mileage, but reduces excessive wear on the tires as well. It’s also less stressful on the vehicle’s brakes because there’s less weight for it to stop.
  • Simpler to repair: As we discussed above, it’s usually not worth it to repair a cast iron engine block. That’s not the case with aluminum blocks. It’s easier to fix aluminum blocks if there’s an issue with the cylinders.
  • Superior heat dissipation: Aluminum rejects heat better than iron, and this can prevent overheating and extend the life of the engine block.


  • Price: An aluminum engine block will almost always cost considerably more than a cast iron engine block.
  • More pliable: Aluminum isn’t as rigid as cast iron, so it’s more subject to warping when it’s put under stress and heat.
  • Weaker power: If you’re looking for peak horsepower, you might want to pass on an aluminum engine block.
  • Might require sleeving: Oftentimes people will use cast iron sleeves to line the cylinders of the engine. This can present a problem because you have two different types of metals being heated and cooled at different heat retention rates, and that could lead to uneven wear and eventual damage.

Call for engine block repair today

Now that you’ve seen the pros and cons of iron vs. aluminum engine blocks, give Auto Truck Service Inc. a call for engine service and repair. We have over 40 years of auto repair experience, and we can repair any vehicle you have, from a commercial truck to your own personal fishing boat.

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