Engine Cylinder Head

What Is an Engine Cylinder Head?

The engine cylinder head sits atop the engine block, sealing the combustion chambers and housing many of the components essential to the four-stroke cycle — intake and exhaust valves, valve springs, camshaft(s) on overhead-cam designs, and the passages that route fuel-air mixture in and spent exhaust gases out. It is one of the most structurally and thermally demanding components in any engine, and its design has a direct impact on power output, fuel efficiency, and long-term engine health.

Why the Cylinder Head Matters

Port shape, combustion chamber volume, valve sizing, and the overall flow characteristics of a cylinder head collectively determine how efficiently an engine breathes. A well-designed head allows the engine to ingest a larger volume of air and fuel and expel exhaust gases more completely — translating directly into torque and horsepower. Whether you are restoring a classic muscle car, building a dedicated race engine, or simply replacing a cracked or warped OEM head, choosing the right cylinder head for your application is one of the highest-impact decisions you can make during an engine build.

Key Considerations When Shopping for a Cylinder Head

• Material: Cast iron offers durability and is common on stock replacements; aluminum reduces weight and dissipates heat more rapidly, making it popular in performance builds.
• Chamber Volume (cc): Combustion chamber volume directly affects compression ratio. Matching chamber cc to your pistons and block deck height is critical for hitting your target compression.
• Port Flow (CFM): Airflow ratings measured on a flow bench indicate how freely air can move through the intake and exhaust ports — a key metric for performance applications.
• Valve Size: Larger valves improve flow at high RPM but can sacrifice low-end torque. Match valve sizing to your cam profile and intended RPM range.
• Bare vs. Assembled: Assembled heads come ready to install with valves, springs, and retainers installed. Bare heads give builders the flexibility to spec their own valvetrain components.

Top Brands in Engine Cylinder Heads

Speedmaster is the dominant name in this category, offering an extensive lineup of aluminum performance cylinder heads for popular small-block and big-block applications. Speedmaster heads are engineered to deliver meaningful airflow improvements over stock castings, making them a go-to choice for street performance and budget-conscious engine builders alike.

Airflow Research (AFR) is renowned in racing circles for CNC-ported cylinder heads with exceptional out-of-the-box flow numbers. AFR's meticulous attention to port geometry has earned the brand a strong following among serious engine builders chasing maximum power.

ARP brings its world-class fastener engineering to the cylinder head category, supplying the high-strength head bolts and studs that keep head gaskets sealed under extreme cylinder pressures. ARP hardware is a natural complement to any cylinder head installation, especially in boosted or high-compression builds.

S&S Cycle serves the powersports market with precision-engineered cylinder heads designed for Harley-Davidson V-Twin applications, combining improved airflow with reliability for street and performance riders.

ITM rounds out the category with a broad selection of OEM-quality replacement cylinder heads, providing dependable, cost-effective solutions for everyday repair and engine rebuilds across a wide range of domestic and import vehicles.