What is the correct valve clearance?

Valve clearance refers to the small gap between the valve and the camshaft in an internal combustion engine. Maintaining the correct valve clearance is crucial for optimal engine performance and longevity. In this article, we'll explore the importance of proper valve clearance and provide guidance on how to ensure it is set correctly.

What is Valve Clearance?

Valve clearance is the small gap that exists between the valve stem and the rocker arm or camshaft. This clearance allows the valve to open and close smoothly, preventing the valve from sticking or causing damage to the engine components. The specific valve clearance required varies depending on the engine design and manufacturer's recommendations.

Why is Proper Valve Clearance Important?

Maintaining the correct valve clearance is essential for several reasons:

• Engine Performance: Improper valve clearance can lead to reduced engine power, decreased fuel efficiency, and increased emissions.


• Engine Longevity: If the valve clearance is too tight, it can cause the valves to stick, leading to engine damage. If the clearance is too loose, it can cause the valves to slam against the cylinder head, also leading to engine damage.


• Noise and Vibration: Incorrect valve clearance can result in increased engine noise and vibration, which can be both annoying and potentially damaging to the engine components.

Therefore, it is essential to ensure that the valve clearance is set according to the manufacturer's specifications to maintain optimal engine performance and longevity.

How to Check and Adjust Valve Clearance

Checking and adjusting the valve clearance typically involves the following steps:

1. Consult the manufacturer's service manual to determine the correct valve clearance specifications for your engine.


2. Locate the valve cover and remove it to access the valves.


3. Use a feeler gauge to measure the clearance between the valve stem and the rocker arm or camshaft.


4. If the clearance is not within the specified range, adjust the valve clearance by loosening the locknut and turning the adjustment screw until the correct clearance is achieved.


5. Repeat the process for all the valves in the engine.


6. Once all the valves have been adjusted, replace the valve cover and ensure that it is properly sealed.

It's important to note that the specific steps for checking and adjusting valve clearance may vary depending on the engine design and manufacturer. Always refer to the service manual for your specific vehicle or engine for detailed instructions.

Conclusion

Proper valve clearance is essential for maintaining optimal engine performance and longevity. By understanding the importance of valve clearance and following the manufacturer's recommendations for checking and adjusting it, you can help ensure your engine runs smoothly and efficiently for years to come.

Is it better to have tight or loose valve clearance?

The proper valve clearance is preferred. The less clearance you have the less time you have to build compression, meaning less power. Also the less clearance the more prone to valve float you have at higher rpms. You are giving bad advice.

What is the proper valve clearance?

Measure the Gap Use a feeler gauge to measure the gap between the valve and rocker arm. Typical clearance: 0.10 to 0.40 mm (check your engine specs). Adjust If Needed Turn the adjustment screw or nut to either widen or narrow the gap. Lock it in place once the correct clearance is achieved.

How do you know if valve clearance is incorrect?

Symptoms of bad valve clearance include engine noise like ticking or clattering, poor engine performance such as loss of power, rough idle, or misfires, and increased fuel consumption. If the clearance is too loose, you'll hear mechanical noises, while if it's too tight, the valves may not close completely, leading to performance issues.
 
Symptoms of loose valve clearance (too much gap)

• Engine noise: A loud ticking or clattering sound, especially from the top of the engine, due to parts like the tappets hitting the valve stems. 
• Reduced performance: In extreme cases, components can wear out or even become dislodged, and the valve will take longer to open, leading to poor engine performance. 
• Increased wear: This can cause excessive wear on components like tappets, pushrods, and valve stems. 

Symptoms of tight valve clearance (too little gap)

• Engine noise: A ticking or knocking sound from the upper part of the engine. 
• Poor performance: The engine may have a rough idle, misfire, difficulty starting, or a loss of power because the valve cannot close completely. 
• Burning valves: A valve that doesn't close properly can be burned by hot combustion gases, which can lead to a loss of compression, increased emissions, and even backfiring. 
• Increased fuel consumption: With a constantly open valve, the engine's efficiency is reduced, leading to higher fuel consumption. 

General symptoms of both problems

• Reduced power and acceleration: The engine may feel sluggish. 
• Increased fuel consumption: The engine uses more fuel than it should. 
• Excessive smoke: You may notice blue smoke from the exhaust, especially if a valve is burning. 
• Misfires or rough idle: The engine may not run smoothly. 

How to properly set a valve lash?

Valve lash adjustment involves setting the clearance between the rocker arm and the valve stem, typically using a feeler gauge. This is done when the engine is off and after positioning the engine so that the specific cam lobe is on its "base circle," meaning the valve is closed. You adjust the rocker arm until the specified feeler gauge has a slight drag between the rocker and the valve stem.
 
Tools and preparation

• Tools: You will need a set of feeler gauges and the appropriate wrenches or sockets for your engine's adjuster nuts. 
• Safety: Disconnect the spark plug wires and remove the valve cover(s) to access the rocker arms and valve stems. 
• Engine position: Rotate the engine by hand until the desired cam lobe is on its base circle. You can do this by watching the rocker arms: 
  • To adjust the intake valve: Rotate the engine until the exhaust valve just starts to open. At this point, the intake valve is closed and the cam lobe is on its base circle. 
  • To adjust the exhaust valve: Rotate the engine until the intake valve is fully open and then slowly let it close, or rotate until the intake valve is about two-thirds closed. At this point, the exhaust valve is closed and the cam lobe is on its base circle. 

This video demonstrates the process of valve lash adjustment: 1:00Resilient Automotive PerformanceYouTube · Jan 2, 2023
Adjustment process

1. Check the gap: Place the feeler gauge with the thickness specified by the manufacturer between the rocker arm and the valve stem. 
2. Loosen the lock nut: Loosen the lock nut on the rocker arm assembly so the adjuster can move freely. 
3. Adjust the clearance: 
   • Hold the adjuster with one wrench and tighten the lock nut with another, or tighten the adjusting screw. 
   • Adjust the screw until the feeler gauge can slide between the rocker and valve stem with a slight drag, but without being forced. 
4. Tighten the lock nut: While holding the adjuster with one wrench, tighten the lock nut to secure the adjustment. 
5. Re-check: Remove the feeler gauge and double-check the clearance. It should still have a light drag. A feeler gauge that is just 1-2 thousandths of an inch thicker should not fit. 
6. Repeat: Repeat the process for each valve in the engine, making sure to position the engine correctly for each one.