Mechanics

Cylinder Head

Step by step explanation of how an automotive engine cylinder head works. This information pertains to most internal combustion engines.

Step 1 - An automotive engine cylinder head performs many tasks such as holding and controlling the combustion process while allowing intake and exhaust gases to enter and exit the cylinder head. Featured in the image below is a cross section of a cylinder head that incorporates intake and exhaust ports and valves. Fastened to the engine block using a head gasket that is tightened (torque) with head bolts, a cylinder head also accommodates the intake and exhaust manifolds. These manifolds are sealed to the head using intake and exhaust manifold gaskets.


Cylinder Head Cut-Away

Step 2 - A cylinder head also holds the camshaft (OHC engines only) timing chains with guides while accompanying the camshaft phaser-acuator.


Camshaft Phaser-Actuator Cut-Away

Step 3 - Engine oil pressure is used to activate the camshaft actuator which is control by the computer.

 
Camshaft Actuator Control Valve


Step 4 - A head gasket is used to seal the cylinder head to the engine block which completes the engine mechanism. The head gasket seals combustion, coolant and engine oil ports.


Cylinder Head w/Engine Block and Piston Cut-Away

Step 5 - The combustion chamber is made up of three items, the piston, engine block and cylinder head. This area is where the combustion process is transformed into thrust once the fuel air mixture is ignited by the spark plug.


Combustion Chamber Cut-Away

Step 6 - A rocker arm and valve spring is used to open and close intake and exhaust valves via the camshaft. The valve spring retainer uses valve keepers which hold the spring to the valve. The rocker arm is used to transfer force from the camshaft to the valve spring.


Rocker Arm and Valve Spring Cut-Away

Step 7 - The lifter is controlled by oil pressure which is used to adjust the gap between the camshaft and the rocker arm. A camshaft timer is used along with sensors to send feedback data to the computer.


Camshaft Timer and Lifter Cut-Away

Step 8 - Camshaft position sensors are used to sense the rotation and position of the camshafts. This data is then used by the main computer to adjust the system for optimal performance.


Camshaft Position Sensors

Step 9 - Ignition coils are used to ignite the combustion mixture and are mounted onto the cylinder head which are connected to the spark plugs.


Ignition Coils

Step 10 - A valve cover is used to control oil and internal crankcase pressure fumes. This cover is sealed to the cylinder head using a valve cover gasket.


Valve Cover and Engine Vent Cut-Away


Helpful Information

A cylinder head is constructed of cast aluminum or iron which are designed to operate at a particular temperature range. If this range is exceeded (overheated) the head can become cracked or the head gasket could fail causing a malfunction such as coolant in the engine oil. An automotive engine depends on the cylinder head operating correctly for example, if intake valve has become worn or damaged, it can cause the engine to idle rough due to leaking gases contaminating the combustion process.

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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