Cast Iron Vs Aluminum Cylinder Heads

Cylinder heads play a vital role in the function of an internal combustion engine.  Often referred to by car enthusiasts as simply “heads”, the cylinder head is located above the cylinders which are on top of the cylinder block.  Cylinder heads house the spark plug that is needed to create the explosion necessary to move the pistons, creating mechanical energy for the engine.  There are several different types of cylinder heads on the market each with their own unique properties that affect engine performance.  A common question that is asked within the automobile industry is which type of cylinder head is the better performer, cast iron or aluminum.  This is a question that is not easily answered as it depends on a number of factors.

The difference between the two types of cylinder heads goes beyond the material used to make them.  Both cast iron and aluminum cylinder heads have their own benefits as well as drawbacks.  The question of which type of head is better really depends on the intended purpose of the  vehicle.

Cast iron cylinder heads have been around for a long time and some people will say they are better then aluminum heads.  In some situations they would be right, but not all.  Here we look at some of the differences between the two and why one might be better than the other in certain applications.

Cast Iron Cylinder Heads

Used for both racing and passenger vehicles, cast iron cylinder heads are generally considered more durable and believed to make more power due to the fact that the chamber holds in heat.  As one would guess from the material used in manufacturing, cast iron cylinder heads are heavier than their aluminum counterparts which usually weigh at least 50% less than the cast iron cylinder heads.  Cast iron cylinder heads are often preferred by day-to-day drivers who find them to be cheaper and less expensive to maintain as they tend to have fewer cracks and blown gaskets.  On the down side, when cast iron cylinder heads do require attention it can be not only time consuming but expensive to repair.  Despite being preferred by day-to-day drivers looking for an inexpensive and durable cylinder head, cast iron cylinder heads are also used in racing vehicles.  In fact, certain race tracks are mandated as “iron only”.

Aluminum Cylinder Heads

Aluminum cylinder heads are popular among much of the racing set as they are lightweight, and produce more torque than cast iron cylinder heads.  Despite the issue of dissipating heat, aluminum cylinder heads are usually easier (less expensive) to repair than cast iron cylinder heads.  Close attention must be paid to certain areas such as fastener tightening procedures and issues with valve lash that result from the expansion of aluminum under normal operating temperatures.

In general both types of cylinder heads can be beneficial depending on what type of performance you are expecting from your vehicle.  Understanding how each work and the benefits and drawbacks will help you better determine which type of cylinder head will best suit your needs.

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One Response to Cast Iron Vs Aluminum Cylinder Heads

  1. Adam says:

    I’m a muscle car car guy, but the BMW engines are magnesium and aluminum engine blocks which allows for lighter weight, and durability for the engine. Lets be honest these new cast aluminum engines last well past 100,000 miles. Back in the 60’s if you got an engine up to 100,000 miles, you did good.

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