Cylinder Head

Functions of the Cylinder Head:

1. Seals the Combustion Chamber – Forms the top enclosure for cylinders, maintaining compression.

2. Houses Valves & Valve Train – Contains intake and exhaust valves, valve guides, springs, and often the camshaft(s) (in OHC engines).

3. Facilitates Air/Fuel Flow – Intake ports direct air/fuel mixture in; exhaust ports expel burnt gases.

4. Supports Cooling & Lubrication – Contains coolant passages (jackets) and oil galleries.

5. Mounts Spark Plugs/Injectors – In gasoline engines, spark plugs thread into the head; in diesels, fuel injectors mount here.

Key Components of a Cylinder Head:

• Valves (Intake & Exhaust) – Control airflow in/out of the combustion chamber.

• Valve Seats – Hardened rings where valves seal.

• Valve Guides – Tubes ensuring proper valve alignment.

• Camshaft(s) – Present in OHC (Overhead Cam) designs (SOHC/DOHC).

• Rocker Arms & Shafts – Used in OHV (Overhead Valve) and some OHC engines.

• Combustion Chamber – The shaped cavity where ignition occurs.

• Ports & Manifold Mounting Flanges – Connect to intake and exhaust manifolds.

Types of Cylinder Heads:

1. Flathead (Side-Valve) – Valves in the block (obsolete, simple but inefficient).

2. Overhead Valve (OHV/Pushrod) – Valves in the head, operated by pushrods and rockers.

3. Overhead Cam (OHC) – Camshaft(s) in the head:

• SOHC (Single Overhead Cam) – One camshaft for both intake/exhaust valves.

• DOHC (Dual Overhead Cam) – Separate cams for intake and exhaust (common in performance engines).

Common Materials:

• Cast Iron – Durable and heat-resistant but heavy (common in older engines).

• Aluminum Alloy – Lightweight, better heat dissipation (modern engines).

Common Cylinder Head Problems:

1. Cracking – Due to overheating or poor casting.

2. Warping – Caused by overheating or improper torque sequence.

3. Valve Seat/Guide Wear – Leads to poor compression or oil burning.

• Blown Head Gasket – Often due to overheating or improper installation.

• Carbon Buildup – Blocks ports or disrupts airflow.

Maintenance & Repair:

• Regular Inspection – Check for leaks, cracks, or warping.
  

• Proper Torque Sequence – Critical when reinstalling to prevent warping.

• Valve Lash Adjustment – Ensures proper valve operation (in OHV/OHC engines).
  

• Decarbonization – Cleaning intake/exhaust ports and valves.
  

• Pressure Testing – Checks for cracks or leaks in coolant/oil passages.

Performance Upgrades:

• Porting & Polishing – Smoothing airflow paths for better efficiency.

• High-Flow Valves – Larger or better-designed valves for increased power.

• Aftermarket Heads – Aluminum heads for weight reduction and cooling.

Specification Of Cylinder Head