Cylinder Head Valves Explained | Intake & Exhaust Valves Working in Car Engine

Описание: 🔧 Complete Information About Cylinder Head Valves

Cylinder head valves are critical engine components mounted in the cylinder head. Their main job is to control the flow of air-fuel mixture into the cylinder and exhaust gases out of the cylinder. Proper valve operation is essential for engine power, fuel efficiency, and emission control.


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1️⃣ What Are Cylinder Head Valves?

Cylinder head valves are mechanically operated poppet valves that open and close at precise times during engine operation. They seal the combustion chamber and ensure correct gas exchange during the four-stroke cycle.

Each cylinder generally has:

Intake valve(s) – allows fresh air or air-fuel mixture in

Exhaust valve(s) – releases burnt gases out



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2️⃣ Types of Valves in Cylinder Head

🔹 Intake Valve

Allows air or air-fuel mixture to enter the cylinder

Usually larger in diameter than exhaust valve

Operates at lower temperature

Made for smooth airflow


🔹 Exhaust Valve

Allows burnt gases to exit the cylinder

Smaller in size

Works at very high temperature

Made from heat-resistant alloy steel



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3️⃣ Valve Construction & Parts

A typical engine valve consists of:

🧩 Valve Head

Flat or tulip-shaped

Seals combustion chamber

Contacts valve seat


🧩 Valve Stem

Long shaft guiding valve movement

Slides inside valve guide


🧩 Valve Face

Sealing surface between valve and valve seat

Must be perfectly smooth


🧩 Valve Tip

Upper end of stem

Contacts rocker arm or cam follower



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4️⃣ Valve Operating Mechanism (Valve Train)

Valves are operated by the valve train, which includes:

Camshaft

Tappet / Lifter

Pushrod (in OHV engines)

Rocker arm

Valve spring


⚙️ Working:

1. Camshaft lobe pushes the valve open


2. Valve spring compresses


3. After cam lobe rotates away, spring closes the valve


4. Valve seals combustion chamber tightly




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5️⃣ Valve Timing (Basic Concept)

Valve timing ensures valves open and close at the correct crankshaft angle.

Intake valve opens before TDC

Intake valve closes after BDC

Exhaust valve opens before BDC

Exhaust valve closes after TDC


This improves volumetric efficiency and power output.


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6️⃣ Number of Valves per Cylinder

2-valve engine – 1 intake + 1 exhaust

3-valve engine – 2 intake + 1 exhaust

4-valve engine – 2 intake + 2 exhaust (most common today)

5-valve engine – Rare, high-performance engines


More valves = better airflow = better performance.


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7️⃣ Valve Materials

Valves are made from:

Nickel-chromium alloy steel

Stainless steel

Sodium-filled exhaust valves (for cooling in high-performance engines)



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8️⃣ Valve Cooling Methods

Heat transfer through valve seat

Heat transfer through valve guide

Sodium-filled hollow valves (exhaust)



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9️⃣ Common Valve Problems

Problem Cause

Burnt valve Overheating, poor seating
Bent valve Timing belt/chain failure
Valve leakage Worn valve seat
Valve sticking Carbon deposits
Tappet noise Incorrect valve clearance



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🔟 Valve Clearance (Valve Lash)

Valve clearance is the small gap between valve tip and rocker arm.

Needed for thermal expansion

Incorrect clearance causes:

Noise (too much)

Power loss or burnt valves (too little)




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1️⃣1️⃣ Importance of Cylinder Head Valves

Controls combustion process

Maintains engine compression

Affects power, mileage, and emissions

Essential for smooth engine operation



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🔚 Conclusion

Cylinder head valves are precision-engineered components that play a vital role in engine breathing and combustion efficiency. Proper valve design, timing, clearance, and maintenance are crucial for engine durability and performance.

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