How to Check Valve Clearance: A Comprehensive Guide

Valve clearance, or lash, is the small gap between the valve stem and the rocker arm or tappet that actuates it; checking valve clearance is a crucial maintenance task that ensures your engine runs smoothly and efficiently, preventing premature wear and costly repairs. CARDIAGTECH.NET provides the tools and knowledge you need to perform this essential task with confidence and precision, maximizing engine performance and longevity. Keeping the proper adjustment extends engine life, increases efficiency and maintains top performance.

1. What is Valve Clearance and Why is it Important?

Valve clearance is the small gap between the valve stem and the rocker arm or tappet, essential for proper engine function. According to a study by the Society of Automotive Engineers (SAE), maintaining proper valve clearance is critical for optimal engine performance and longevity. Inaccurate clearance can lead to reduced power, increased fuel consumption, and even engine damage.

Ensuring Proper Valve Seating: The gap ensures the valve can fully close, maintaining compression and preventing leaks.
Accommodating Thermal Expansion: Engine components expand when heated; the clearance allows for this expansion without causing valves to stay open.
Preventing Valve Train Damage: Too little clearance can cause valves to remain open, leading to overheating and potential damage to the valve train components.

2. Understanding Valve Clearance: A Deep Dive

Valve clearance, also known as valve lash, is a critical adjustment in internal combustion engines. It refers to the small gap between the valve stem and the rocker arm (or tappet) that actuates the valve. This clearance is essential for the proper operation of the engine, ensuring that valves open and close at the correct times and seal tightly when closed.

2.1. Why is Valve Clearance Necessary?

The need for valve clearance arises from several factors related to engine operation and design:

Thermal Expansion: Engine components, especially valves, undergo significant thermal expansion as the engine heats up. Without adequate clearance, the valves may not fully close when hot, leading to compression loss and potential engine damage.
Wear and Tear: Over time, engine components wear down. Valve seats recede, valve faces wear, and other parts of the valve train can change dimensions. Valve clearance provides a buffer that accommodates these changes, maintaining proper valve timing and sealing.
Valve Train Dynamics: The valve train is a dynamic system with rapidly moving parts. Valve clearance allows these parts to move freely without binding or excessive stress, which could lead to premature wear or failure.

2.2. Types of Valve Train Systems

The specific valve clearance requirements and adjustment methods vary depending on the type of valve train system used in the engine. The most common types include:

Overhead Valve (OHV) Systems: In OHV engines, the camshaft is located in the engine block, and pushrods and rocker arms transmit motion to the valves in the cylinder head. Valve clearance is typically adjusted using screws and locknuts on the rocker arms.
Overhead Cam (OHC) Systems: OHC engines have the camshaft(s) located in the cylinder head, directly above the valves. This design eliminates the need for pushrods, resulting in a more direct and responsive valve train. Valve clearance in OHC engines can be adjusted using shims, screws, or hydraulic lifters.
- Shim-Under-Bucket: Shims are located between the valve stem and the bucket-shaped tappet.
- Shim-Over-Bucket: Shims are located on top of the bucket tappet, between the tappet and the cam lobe.
- Screw-Type: Adjustment is made with a screw and locknut on the rocker arm.

2.3. Consequences of Incorrect Valve Clearance

Maintaining proper valve clearance is crucial for engine health and performance. The consequences of incorrect valve clearance can be severe:

Too Little Clearance (Tight Valves):
- Burnt Valves: Valves may not fully seat, allowing hot combustion gases to escape and overheat the valve, leading to burning and distortion.
- Reduced Compression: Poor valve sealing results in compression loss, reducing engine power and efficiency.
- Engine Damage: Over time, tight valves can cause significant damage to the valve train, including bent valves, worn valve guides, and damaged camshaft lobes.
Too Much Clearance (Loose Valves):
- Noisy Operation: Excessive clearance causes the valve train to be noisy, with a noticeable ticking or clattering sound.
- Reduced Valve Lift: The valve may not open fully, reducing airflow into and out of the cylinder, which decreases engine power and efficiency.
- Valve Train Wear: The increased impact and stress on valve train components can accelerate wear and tear, leading to premature failure.

2.4. Factors Affecting Valve Clearance

Several factors can influence valve clearance over time, necessitating periodic checks and adjustments:

Engine Wear: As engine components wear, valve seats recede, valve faces wear, and camshaft lobes degrade, all of which affect valve clearance.
Thermal Cycling: Repeated heating and cooling of engine components can cause changes in dimensions, altering valve clearance.
Component Manufacturing Tolerances: Even new engines can have slight variations in valve clearance due to manufacturing tolerances.
Fuel Type and Combustion Characteristics: Different fuel types and combustion processes can affect valve temperatures and wear rates, influencing valve clearance.

2.5. Symptoms of Incorrect Valve Clearance

Recognizing the symptoms of incorrect valve clearance is essential for timely maintenance and repair:

Engine Noise: Ticking, clicking, or clattering sounds from the valve train.
Reduced Engine Performance: Loss of power, poor acceleration, and decreased fuel efficiency.
Rough Idle: Unstable or erratic idle speed.
Difficulty Starting: Hard starting, especially when the engine is cold.
Increased Emissions: Higher than normal levels of exhaust emissions.

2.6. The Role of Precision Tools in Measuring Valve Clearance

Ensuring accurate valve clearance is paramount for optimal engine performance and longevity. High-precision tools are essential in this process, providing the accuracy needed to achieve the correct settings. Here’s why these tools are so important:

Feeler Gauges: These are thin strips of metal with precise thicknesses, used to measure the gap between the valve stem and rocker arm. Accurate feeler gauges ensure the clearance is within the manufacturer’s specified range.
Micrometers: Used to measure the thickness of shims in engines with shim-adjusted valve trains. A high-quality micrometer provides precise measurements, allowing for accurate selection of replacement shims.
Torque Wrenches: Essential for tightening the locknuts on rocker arms or camshaft bolts to the manufacturer’s specified torque. Proper torque ensures that the adjustment remains stable and prevents damage to the components.
Dial Indicators: Useful for verifying camshaft lift and timing, ensuring that the camshaft is operating correctly and that the valve train is properly synchronized.

Using high-precision tools ensures that valve clearance adjustments are made accurately, leading to improved engine performance, reduced wear, and enhanced reliability. Investing in quality tools from CARDIAGTECH.NET is a smart choice for any mechanic or serious DIY enthusiast.

3. Essential Tools for Checking Valve Clearance

To accurately check and adjust valve clearance, you’ll need a few specialized tools. CARDIAGTECH.NET offers a comprehensive selection of high-quality tools to make this task easier and more precise.

Tool	Description	Why It’s Important
Feeler Gauges	Thin, calibrated metal strips used to measure the gap between the valve stem and rocker arm.	Ensures accurate measurement of valve clearance. Different sizes are needed to match the manufacturer’s specifications.
Socket Set	A set of sockets and wrenches for removing and installing valve covers and other engine components.	Provides the leverage and grip needed to loosen and tighten bolts without damaging them. Metric sizes are typically required for most engines.
Torque Wrench	A wrench that measures and applies a specific amount of torque to fasteners.	Ensures that bolts are tightened to the manufacturer’s specified torque, preventing damage to the valve cover and ensuring a proper seal.
Screwdrivers	Both flathead and Phillips head screwdrivers for removing various engine components.	Useful for removing hoses, clips, and other small parts that may be in the way. A variety of sizes is helpful for different applications.
Micrometer	Used to measure the thickness of shims when adjusting valve clearance in engines with shim-adjusted valve trains.	Provides precise measurements needed to select the correct replacement shims. Digital micrometers offer the highest accuracy.
Magnetic Pickup Tool	A tool with a magnetic tip used to retrieve dropped parts from hard-to-reach areas.	Prevents lost parts from falling into the engine and causing damage. Essential for working in tight engine compartments.
Inspection Mirror	A small mirror on an adjustable handle used to inspect hard-to-see areas of the engine.	Allows you to visually inspect valve train components for wear or damage. Helpful for identifying potential issues before they become major problems.
Parts Tray	A container to hold small parts, bolts, and shims during disassembly and reassembly.	Prevents lost parts and keeps everything organized. Multiple compartments can help you keep track of parts in the order they were removed.
Service Manual	A manual specific to your vehicle’s make and model that provides detailed instructions and specifications for valve clearance.	Provides the correct valve clearance specifications, torque values, and step-by-step instructions for your engine. Essential for ensuring the job is done correctly.
RTV Silicone Sealant	Used to seal the valve cover gasket to the engine.	Prevents oil leaks from the valve cover. Ensure the sealant is compatible with your engine and follows the manufacturer’s recommendations.
Cleaning Supplies	Cleaning solvents, rags, and brushes to clean the valve cover and engine surfaces.	Removes dirt and debris that can contaminate the engine and prevent a proper seal. A clean working environment ensures accurate measurements and prevents damage to engine components.

For professionals and DIY enthusiasts alike, CARDIAGTECH.NET offers a range of diagnostic tools and equipment that will keep your garage operating at peak efficiency. Contact us at +1 (641) 206-8880 to find out more and make a purchase.

4. Step-by-Step Guide: How to Check Valve Clearance

Here’s a detailed, step-by-step guide on how to check valve clearance, incorporating best practices and safety tips. Always consult your vehicle’s service manual for specific instructions and torque specifications.

4.1. Preparation

Gather Tools and Supplies:
- Feeler gauges (various sizes)
- Socket set and wrenches
- Torque wrench
- Screwdrivers (flathead and Phillips)
- Micrometer (if adjusting shims)
- Magnetic pickup tool
- Inspection mirror
- Parts tray
- Service manual for your vehicle
- RTV silicone sealant
- Cleaning solvents, rags, and brushes
Safety First:
- Allow the engine to cool completely before starting. Working on a hot engine can cause burns.
- Disconnect the negative battery cable to prevent accidental electrical shorts.
- Wear safety glasses and gloves to protect yourself from debris and chemicals.
Prepare the Work Area:
- Park the vehicle on a level surface and engage the parking brake.
- Ensure adequate lighting and ventilation in your work area.
- Cover fenders with protective covers to prevent scratches.

4.2. Accessing the Valves

Remove Components:
- Remove any components that block access to the valve cover, such as the air filter assembly, hoses, or wiring harnesses.
- Carefully disconnect any electrical connectors attached to the valve cover.
Clean the Valve Cover:
- Use a brush and cleaning solvent to remove any dirt, oil, or debris from the valve cover. This prevents contaminants from entering the engine when the cover is removed.
Remove the Valve Cover:
- Loosen the valve cover bolts in a crisscross pattern to prevent warping.
- Once all bolts are loose, carefully remove the valve cover.
- Inspect the valve cover gasket. If it’s damaged or worn, replace it with a new one.

4.3. Setting the Engine to Top Dead Center (TDC)

Locate the Crankshaft Pulley:
- Identify the crankshaft pulley on the front of the engine.
Remove the Timing Cover:
- Remove the timing cover to expose the timing marks on the crankshaft pulley.
Rotate the Engine:
- Use a socket and wrench to rotate the crankshaft clockwise until the timing mark aligns with the TDC mark on the engine block. Consult your service manual for the exact location of the TDC mark.
Verify TDC on Cylinder 1:
- Remove the spark plug from cylinder 1.
- Insert a long screwdriver or dowel into the spark plug hole.
- Gently rotate the crankshaft back and forth. The screwdriver or dowel should rise to its highest point when the engine is at TDC on cylinder 1.
Check Camshaft Position:
- Ensure that the camshaft lobes for cylinder 1 are pointing away from the valves, indicating that both valves are closed.

4.4. Measuring Valve Clearance

Consult Service Manual:
- Refer to your service manual for the specified valve clearance range for your engine (both intake and exhaust valves).
Insert Feeler Gauge:
- Select a feeler gauge that is within the specified clearance range.
- Gently insert the feeler gauge between the valve stem and the rocker arm (or tappet).
Check the Fit:
- The feeler gauge should slide in with a slight drag. If it slides in too easily, the clearance is too large. If it doesn’t fit at all, the clearance is too small.
Record Measurements:
- Record the valve clearance measurements for each valve in a notebook or on a worksheet. Be sure to label each measurement with the corresponding cylinder number and valve type (intake or exhaust).
Repeat for All Valves:
- Rotate the crankshaft to bring each cylinder to TDC and repeat the measurement process for all valves.

4.5. Adjusting Valve Clearance (If Necessary)

Determine Adjustment Method:
- Consult your service manual to determine the correct method for adjusting valve clearance on your engine (e.g., adjusting screws, shims, hydraulic lifters).
Adjusting Screws:
- Loosen the locknut on the rocker arm adjusting screw.
- Turn the adjusting screw to increase or decrease the valve clearance as needed.
- Use the feeler gauge to verify the clearance.
- Tighten the locknut while holding the adjusting screw in place.
- Recheck the clearance after tightening the locknut.
Replacing Shims:
- Remove the camshaft(s) to access the shims (refer to your service manual for detailed instructions).
- Measure the thickness of the existing shims using a micrometer.
- Calculate the required shim thickness to achieve the correct valve clearance.
- Install the new shims.
- Reinstall the camshaft(s).
- Recheck the valve clearance.
Hydraulic Lifters:
- Hydraulic lifters typically do not require manual adjustment. If a hydraulic lifter is not functioning properly, it may need to be replaced.

4.6. Reassembly

Clean Mating Surfaces:
- Clean the valve cover and cylinder head mating surfaces with a clean rag and solvent to remove any old gasket material or debris.
Install New Gasket:
- Install a new valve cover gasket.
Apply Sealant:
- Apply a thin layer of RTV silicone sealant to the corners and along any seams in the cylinder head.
Reinstall Valve Cover:
- Carefully reinstall the valve cover, ensuring that the gasket is properly seated.
Tighten Bolts:
- Tighten the valve cover bolts in a crisscross pattern to the manufacturer’s specified torque.
Reconnect Components:
- Reconnect any components that were removed to access the valve cover, such as hoses, wiring harnesses, and the air filter assembly.
Reconnect Battery:
- Reconnect the negative battery cable.

4.7. Final Checks

Start Engine:
- Start the engine and allow it to run for a few minutes.
Check for Leaks:
- Inspect the valve cover for any oil leaks.
Listen for Unusual Noises:
- Listen for any unusual noises from the valve train.
Test Drive:
- Take the vehicle for a test drive to ensure that it is running smoothly and efficiently.

Following these steps carefully will ensure that you accurately check and adjust your valve clearance, maintaining the performance and longevity of your engine.

5. Common Mistakes to Avoid

Checking valve clearance can be a complex task, and it’s easy to make mistakes if you’re not careful. Here are some common pitfalls to avoid:

Skipping the Service Manual:
- Always consult your vehicle’s service manual for specific instructions, torque specifications, and valve clearance ranges.
Working on a Hot Engine:
- Allow the engine to cool completely before starting. Working on a hot engine can cause burns and inaccurate measurements.
Using Incorrect Tools:
- Use the correct tools for the job. Using the wrong tools can damage engine components and lead to inaccurate measurements.
Forgetting to Set TDC:
- Ensure that the engine is at Top Dead Center (TDC) on the compression stroke before measuring valve clearance.
Measuring Clearance Incorrectly:
- Insert the feeler gauge straight and apply slight pressure. The gauge should slide in with a slight drag.
Overtightening Bolts:
- Use a torque wrench to tighten bolts to the manufacturer’s specified torque. Overtightening bolts can damage the valve cover and cylinder head.
Reusing Old Gaskets:
- Always use a new valve cover gasket when reassembling the engine. Old gaskets can leak and cause oil consumption.
Neglecting to Clean Surfaces:
- Clean the valve cover and cylinder head mating surfaces before installing the new gasket.
Skipping Final Checks:
- Start the engine and check for oil leaks and unusual noises after reassembly.

6. The Role of CARDIAGTECH.NET in Ensuring Accurate Valve Clearance

At CARDIAGTECH.NET, we understand the importance of precision and accuracy when it comes to engine maintenance. That’s why we offer a comprehensive range of tools and equipment designed to help you achieve optimal valve clearance settings.

6.1. High-Quality Tools

We offer a wide selection of high-quality tools, including:

Feeler Gauges: Our feeler gauges are made from hardened steel and are calibrated to ensure accurate measurements.
Micrometers: Our micrometers are designed for precise measurement of shims and other engine components.
Torque Wrenches: Our torque wrenches are calibrated to ensure that bolts are tightened to the manufacturer’s specified torque.

6.2. Expert Advice

Our team of experienced technicians can provide expert advice and guidance on how to check and adjust valve clearance on your specific engine. We can also help you select the right tools and equipment for the job.

6.3. Comprehensive Service Manuals

We offer a wide selection of service manuals for various vehicle makes and models. These manuals provide detailed instructions and specifications for valve clearance, as well as other engine maintenance tasks.

6.4. Convenient Online Ordering

Our online store makes it easy to purchase the tools and equipment you need to check and adjust valve clearance. We offer fast shipping and competitive prices.

7. Maintaining Valve Clearance: How Often Should You Check?

Regular maintenance of valve clearance is vital for engine health and longevity. The frequency of these checks can vary based on several factors, but adhering to a consistent schedule helps prevent major issues.

Manufacturer Recommendations: The best guide for how often to check valve clearance is your vehicle’s service manual. Manufacturers specify intervals based on the engine’s design and expected wear.
Driving Conditions: Severe driving conditions, such as frequent stop-and-go traffic, towing, or high-speed driving, can increase engine wear and the need for more frequent checks.
Engine Type: Some engines are more prone to valve clearance changes. For example, engines with solid lifters typically require more frequent adjustments than those with hydraulic lifters.
Symptoms: If you notice symptoms like engine noise (ticking or clattering), reduced performance, or rough idling, it’s time to check the valve clearance, regardless of the regular schedule.

Typical Intervals:

Vehicle Use	Check Interval
Normal driving conditions	Every 20,000 – 30,000 miles
Severe driving conditions	Every 15,000 – 20,000 miles
High-performance/racing engines	Every race or event

By following these guidelines and staying attentive to your engine’s performance, you can maintain proper valve clearance and ensure optimal engine health.

8. Benefits of Maintaining Proper Valve Clearance

Maintaining proper valve clearance offers numerous benefits for your engine and vehicle.

Improved Engine Performance:
- Proper valve clearance ensures that valves open and close at the correct times, optimizing engine performance and power output.
Increased Fuel Efficiency:
- Correct valve timing improves combustion efficiency, resulting in better fuel economy.
Reduced Engine Noise:
- Properly adjusted valves reduce valve train noise, such as ticking or clattering sounds.
Extended Engine Life:
- Maintaining proper valve clearance prevents premature wear and damage to valve train components, extending the life of your engine.
Reduced Emissions:
- Optimized combustion reduces harmful emissions, helping your vehicle meet emissions standards.
Prevention of Costly Repairs:
- Regular valve clearance checks can prevent minor issues from escalating into major repairs, saving you money in the long run.
Smooth Idling:
- Correct valve timing ensures a smooth and stable idle, enhancing driving comfort.
Optimal Valve Seating:
- Proper clearance allows valves to seat correctly, maintaining compression and preventing leaks.

9. How to Troubleshoot Common Valve Clearance Issues?

Troubleshooting valve clearance issues involves recognizing symptoms, pinpointing causes, and applying effective solutions. Here’s a detailed guide:

1. Identifying Symptoms:

Engine Noise: Ticking or clattering sounds, especially when the engine is cold.
Reduced Performance: Loss of power, poor acceleration, and decreased fuel efficiency.
Rough Idle: Unstable or erratic idle speed.
Difficulty Starting: Hard starting, especially when the engine is cold.
Increased Emissions: Higher than normal levels of exhaust emissions.

2. Preliminary Checks:

Review Maintenance Records: Check when the valve clearance was last adjusted.
Inspect Valve Train Components: Look for visible signs of wear or damage on rocker arms, valves, and camshaft lobes.
Listen Carefully: Use a stethoscope or long screwdriver to isolate the source of the noise.

3. Diagnostic Steps:

Measure Valve Clearance: Follow the step-by-step guide in your service manual to measure the clearance for each valve.
Compare Measurements: Compare your measurements to the manufacturer’s specifications. Note any valves that are outside the specified range.
Assess Wear Patterns: Look for patterns of wear that could indicate specific problems.

4. Common Issues and Solutions:

Issue	Probable Cause	Solution
Tight Valve Clearance	Valve seat recession, valve stretch	Replace the affected valves and valve seats.
Loose Valve Clearance	Worn rocker arms, worn camshaft lobes	Replace the worn rocker arms or camshaft.
Worn Shims	Normal wear and tear	Replace the worn shims with new ones of the correct thickness.
Hydraulic Lifter Failure	Dirty oil, mechanical failure	Replace the faulty hydraulic lifter and ensure the oil is clean.
Bent Valves	Over-revving, improper timing	Replace the bent valves and address the cause of the bending. Ensure the timing is correctly set.
Valve Spring Issues	Fatigue, breakage	Replace the worn or broken valve springs.
Camshaft Issues	Bearing failure, lack of lubrication	Inspect the camshaft bearings and replace them if necessary. Ensure the engine is properly lubricated. Replace the camshaft if it is damaged beyond repair.

5. Additional Tips:

Use Quality Parts: When replacing components, use high-quality parts from reputable suppliers like CARDIAGTECH.NET.
Follow Service Manual: Always adhere to the procedures and specifications outlined in your vehicle’s service manual.
Cleanliness: Keep the engine clean during disassembly and reassembly to prevent contamination.
Proper Tools: Use the correct tools for the job to avoid damaging engine components.

By following these troubleshooting steps, you can effectively diagnose and resolve common valve clearance issues, ensuring your engine runs smoothly and efficiently. Remember to consult your service manual for specific guidance and torque specifications.

10. FAQ: Frequently Asked Questions About Valve Clearance

What is valve clearance?
- Valve clearance is the small gap between the valve stem and the rocker arm or tappet that actuates it. This gap ensures proper valve seating and accommodates thermal expansion.
Why is valve clearance important?
- Proper valve clearance ensures optimal engine performance, fuel efficiency, and reduced engine noise. It also extends engine life and reduces emissions.
How often should I check valve clearance?
- Refer to your vehicle’s service manual for the recommended interval. Typically, it’s every 20,000 to 30,000 miles under normal driving conditions.
What are the symptoms of incorrect valve clearance?
- Symptoms include engine noise (ticking or clattering), reduced performance, rough idle, difficulty starting, and increased emissions.
Can I adjust valve clearance myself?
- Yes, if you have mechanical skills and the right tools. However, it’s essential to follow the instructions in your service manual carefully.
What tools do I need to check valve clearance?
- You’ll need feeler gauges, a socket set, a torque wrench, screwdrivers, a micrometer (if adjusting shims), a magnetic pickup tool, and a service manual.
What happens if valve clearance is too tight?
- Tight valve clearance can cause burnt valves, reduced compression, and engine damage.
What happens if valve clearance is too loose?
- Loose valve clearance can cause noisy operation, reduced valve lift, and valve train wear.
Where can I find the correct valve clearance specifications for my engine?
- The correct valve clearance specifications can be found in your vehicle’s service manual.
How can CARDIAGTECH.NET help me with valve clearance?
- CARDIAGTECH.NET offers high-quality tools, expert advice, comprehensive service manuals, and convenient online ordering to help you check and adjust valve clearance accurately. Contact us at +1 (641) 206-8880 for expert assistance and to purchase the tools you need.
Is it better to have slightly loose or slightly tight valve clearance?
- It’s generally better to have slightly loose valve clearance than slightly tight. Tight clearance can lead to valves not fully seating, causing overheating and potential damage. Loose clearance may result in some noise but is less likely to cause severe damage. Always aim for the manufacturer’s recommended range for optimal performance.

Valve clearance is a critical aspect of engine maintenance that should not be overlooked. By understanding the importance of valve clearance, using the right tools, following the correct procedures, and avoiding common mistakes, you can ensure that your engine runs smoothly, efficiently, and reliably for years to come. Trust CARDIAGTECH.NET to provide the tools and knowledge you need to keep your engine in top condition.

Are you ready to ensure your engine’s optimal performance? Contact CARDIAGTECH.NET today at +1 (641) 206-8880 for expert guidance and premium tools that guarantee precision and longevity. Located at 276 Reock St, City of Orange, NJ 07050, United States, we’re here to help you achieve the best results. Don’t wait – invest in your engine’s health now!