Aluminum vs Iron Heads
If we have similar iron and aluminum heads, they would look identical, only the material they are made from would be different. Externally, they both would look same, but internally, they would have different types of spark plugs. Aluminum heads use gaskets that are seat-style long reach, whereas iron heads have a tapered seat-style and short reach spark plugs. There is a famous old theory that aluminum heads have more compression ratio because they dissipate more heat, whereas iron heads are able to make more power since the chamber locks in the heat.
Tests have been carried out several times to prove this theory that aluminum and iron heads have any possibility to ensure that heat retention characteristics would require different ignition timing settings.
Other questions also rise, such as besides heat disbursement, are iron heads better than aluminum heads, and what are the other benefits if we use aluminum heads over iron heads, besides weight? Aluminum is lighter, more ductile, and can be machined rather than cast; iron is more brittle and susceptible to damage due to temperature changes. Aluminum has less weight than iron, and is easier to repair as well.
Many people prefer aluminum heads for their performance, and consider them inherently better than iron heads. However, no matter which material – iron, aluminum or cobalt – is used to build heads, their performance will almost be the same.
From the standpoint of difference between aluminum and iron heads, it would be torque, since the amount of torque makes aluminum win over iron heads. Aluminum heads have higher compression, are lightweight and have better ports when compared to iron heads. However, iron heads are usually preferred by daily drivers, since it does not develop problems like aluminum heads over time. Aluminum heads may have to be removed and repaired more often than iron heads. Iron heads are cheaper than aluminum, and durable as well, since they have fewer blown gaskets and less cracks.
Another reason why iron heads are preferred is that they do not transfer much heat during combustion like aluminum. Iron and aluminum heads have a difference in flow as well. Iron heads have the ability to make more horsepower than aluminum heads, since they have a slight difference in amount of torque. Other than that, there may not be any difference in power.
Summary:
1. Aluminum and iron heads may look the same externally, yet have different spark plugs internally.
2. Aluminum is lightweight and easy to repair.
3. Iron heads are heavier, but more durable.
4. Aluminum heads have a lesser amount of torque, but they release too much heat during combustion.
5. Iron heads store heat in its chamber, are preferred as they require less repairs, and they are also cost saving.