Cylinder Head Showdown: Aluminum or Cast Iron?
Your vehicle's cylinder head (often referred to simply as just "head") seals the top of the engine's combustion chamber. It often serves three basic functions:
- It covers the cylinder bores.
- It holds valves and fuel injectors that determine how much air and fuel enter the cylinders.
- It lets the exhaust out.
Spark plugs and rocker arms are also mounted on the cylinder head. If you're shopping for a new cylinder head, one basic question is whether you should get a cast iron cylinder head, or one made of aluminum. We decided to break it down for you.
Cast iron cylinder heads
- Very durable
- Cheaper to maintain (suffer fewer cracks and blown gaskets)
- More affordable than aluminum cylinder heads
- Cause more heat to be retained in the chamber which may lead to higher power output
- Very heavy, making them less ideal for high-speed applications
- Not able to dissipate heat, leading to lower compression ratios
- While they are easier to maintain, any damage or mechanical problem will cost more and take longer to repair
Cast iron heads are more common and are often preferred by casual drivers.
Aluminum cylinder heads
- Weigh around 50% less than cast iron heads, making them ideal for racing
- Produce more torque
- Good at dissipating heat, allowing for higher compression ratios
- Although not as durable as cast iron, they are easier and cheaper to repair
- Not as sturdy as cast iron and thus more prone to cracks
- Susceptible to head gasket failure when used with iron engine blocks due to the differing expansion rates of aluminum and iron
Newer aluminum alloys have improved durability. Aluminum cylinder heads are ideal for racing and other high-performance applications.
- Many installation sets don't include cylinder head bolts. You will have to purchase the head bolts separately.
- See what kinds of gaskets are included in the cylinder head installation set. Some do not include the exhaust pipe to manifold gasket.
- Refer to your owner manual for specific information regarding which cylinder head will work best with your engine and what components you will need for installation.
How to Replace Your Vehicle's Cylinder Head
The cylinder head seals the top of your engine's combustion chamber. Your cylinder head acts as a gatekeeper, allowing air and fuel into the cylinders while letting engine exhaust escape. Because it is subjected to extreme temperatures and pressure and exposed to different fluids, your cylinder head may crack or corrode over time. It will take some serious mechanical tinkering, but you can spare yourself a lot of cash in repair expenses by replacing the cylinder head yourself.
Difficulty Level: Difficult
Here's what you'll need:
- Wrench and socket set
- Ratchet and ratchet extension set
- Standard and Phillips screwdrivers
- Pry bar
- Breaker bar
- Torque wrench
- Drain pan
- Gasket scraper
- New engine oil
- New antifreeze
- Cylinder head installation set
- New cylinder head bolt (if not included in the kit)
- Vehicle owner manual
NOTE: Make sure your engine has cooled over several hours before starting. It's also a good idea to disconnect the negative cable from the battery terminal.
Step 1: Place the drain pan underneath your radiator. Drain the coolant by opening the drain valve.
Step 2: Using your assortment of tools, remove the throttle body, steering pump mounting bracket, air cleaner system, and any other component that might get in the way of removing the cylinder head. As always, loosening anything involves turning it counterclockwise ("righty = tightey, lefty = loosey").
Step 3: Use your wrench and ratchet set to separate the intake manifold and the exhaust manifold from the cylinder head.
Step 4: Use your ratchet set to remove the valve cover/s.
Step 5: Use your wrench and ratchet set to remove the timing belt or chain.
Step 6: If your cylinder head has a rocker shaft arm, remove.
Step 7: Use your ratchet extension and socket to unscrew the cylinder head bolts. You can use the breaker bar if needed.
Step 8: Lift the cylinder head off your engine block. If necessary, you can use your pry bar to dislodge it.
Step 9: Remove the head gasket and scrape off any traces of it. Wipe the mating surfaces with a rag.
Step 10: Install a new head gasket (the one that came with the installation kit).
Step 11: Install your new cylinder head. Use new cylinder bolts if the old ones can't be reused. Apply engine oil to all the bolts.
Step 12: Put everything back together by following the reverse order of disassembly. Use the torque wrench to tighten the bolts as specified by your manual. Refill your radiator with a coolant mixture of 50% antifreeze and 50% water.
Refer to your vehicle's owner manual for specific details (torque specs, mounting order, etc.) that may require you to deviate from these general instructions.