The engine is the heart of any vehicle, and one of its most crucial components is the cylinder head. While often overlooked by non-mechanics, the cylinder head plays a vital role in engine performance, efficiency, and reliability. Whether you’re a car enthusiast, a mechanic-in-training, or simply curious about how engines work, understanding the different types of cylinder heads can give you valuable insight into the inner workings of vehicles.
In this guide, we’ll explore the 4 main types of cylinder heads, how they differ, their uses, advantages, and what makes each type suitable for specific applications.
What Is a Cylinder Head?
Before diving into the types, let’s quickly define what a cylinder head is. A cylinder head sits on top of the engine block, sealing the combustion chamber. It contains passages for intake and exhaust gases, houses valves and spark plugs, and often includes the camshaft and other critical engine components. The cylinder head forms the top of the combustion chamber and works in tandem with the pistons and cylinder walls to facilitate internal combustion.
A well-designed cylinder head improves airflow, controls emissions, supports efficient fuel combustion, and contributes to overall engine performance.
The 4 Types of Cylinder Heads
Each type of cylinder head has a distinct design and purpose, often depending on the type of engine configuration and intended use. The four main types include:
1. Flathead Cylinder Head
Also known as a “L-head” or “side-valve” engine, the flathead cylinder head is the simplest type and was popular in early automotive history. In this design, the cylinder head itself is a simple metal plate with no moving parts. The valves are located beside the cylinder, within the engine block.
Key Features:
- Very simple and inexpensive to manufacture
- No complex valve train in the head
- Limited performance due to inefficient airflow
Pros:
- Durable and easy to repair
- Compact design with fewer moving parts
- Historically proven design
Cons:
- Poor fuel efficiency
- Lower power output
- Prone to overheating
Flatheads were common in the first half of the 20th century but have since been replaced by more efficient designs in modern vehicles.
2. Overhead Valve (OHV) Cylinder Head
Also called a pushrod engine, the OHV cylinder head features the valves located in the cylinder head itself, with the camshaft located in the engine block. The camshaft pushes rods that actuate rocker arms, opening and closing the valves.
Key Features:
- Valves in the head, camshaft in the block
- Compact vertical profile
- Pushrod design allows smaller engine size
Pros:
- Strong low-end torque
- Reliable and time-tested design
- Easier to maintain and repair
Cons:
- Limited high-RPM performance
- More moving parts compared to OHC designs
- Less efficient airflow than DOHC setups
OHV engines are still used today in various applications, particularly in V8 engines and American-made trucks where low-end power and durability are prioritized.
3. Overhead Camshaft (OHC) Cylinder Head
The OHC design improves upon the OHV design by moving the camshaft from the block to the cylinder head. This allows more direct control of the valves, improving timing precision and reducing the number of moving parts.
There are two main subtypes:
- Single Overhead Camshaft (SOHC) – one camshaft operates both intake and exhaust valves.
- Double Overhead Camshaft (DOHC) – two camshafts, one for intake and one for exhaust valves.
Key Features:
- Camshaft(s) directly control valves
- Improved timing and airflow
- Common in modern 4-cylinder and V6 engines
Pros:
- Better performance and efficiency
- Higher RPM capability
- Smoother operation and precise valve timing
Cons:
- More complex design
- Costlier to manufacture and repair
SOHC heads offer a balance of performance and simplicity, while DOHC heads are preferred for performance and fuel economy in high-revving engines.
4. Hemispherical (Hemi) Cylinder Head
Popularized by Chrysler, the Hemi cylinder head features a hemispherical combustion chamber. This dome-shaped design allows larger valves and better airflow, resulting in increased power and combustion efficiency.
Key Features:
- Hemispherical combustion chamber
- Angled valves for improved airflow
- Typically used in performance or muscle cars
Pros:
- Exceptional performance and power output
- Superior airflow and fuel combustion
- Reduced heat loss due to chamber shape
Cons:
- Complex and bulky design
- Costlier to manufacture
- Heavier than other head types
While not common in everyday vehicles, Hemi heads remain a symbol of raw engine power and are used in performance and racing applications.
How to Choose the Right Cylinder Head
The choice of cylinder head depends largely on your goals:
- For reliability and simplicity, OHV engines with pushrod cylinder heads are a good pick.
- If you’re seeking efficiency and smoothness, modern OHC or DOHC engines are ideal.
- For pure performance, a Hemi head or custom DOHC configuration might be the way to go.
- Flathead designs are more suitable for vintage car restorations or collectors.
Whether you’re rebuilding an engine, modifying for performance, or just learning, understanding these differences is essential.
Cylinder Heads in Motorsports and Custom Builds
Performance enthusiasts often invest in aftermarket cylinder heads to improve airflow, compression, and engine durability. Porting, polishing, and using lightweight materials like aluminum are common practices to get more horsepower and torque from an engine.
Websites like https://behindthe8.ca/ provide automotive insights, tuning advice, and parts resources for custom builds and motorsport upgrades, making them a great place to start for car enthusiasts.
Conclusion
Understanding the four primary types of cylinder heads — Flathead, OHV, OHC, and Hemi — gives you a better appreciation for engine design and performance. Each type offers unique advantages and suits different applications, from classic simplicity to modern high-performance engineering.
When choosing or working with cylinder heads, consider factors like engine layout, performance goals, maintenance ease, and budget. Whether you’re tuning a muscle car, upgrading a daily driver, or just expanding your knowledge, a solid grasp of cylinder head technology is key to unlocking engine potential.
