Valve shimming is an essential maintenance procedure in many internal combustion engines, especially those with adjustable valve clearances.

The process involves adjusting the valve clearances using precision-engineered shims to ensure optimal engine performance and longevity.

Basics of Valve Clearance

Valve clearance refers to the gap between the valve stem and the rocker arm or camshaft. This clearance is critical in allowing the valve to open and close properly as the engine runs.

Over time, wear and tear on the engine components can cause the clearance to change, leading to decreased engine performance and potential damage.

Importance of Valve Adjustment

Adjusting valve clearances is vital for several reasons:

  1. Proper valve clearance ensures optimal fuel combustion and efficient engine performance.
  2. It prevents premature wear on engine components, leading to longer engine life.
  3. Incorrect valve clearance can cause excessive noise, reduced power, and poor fuel efficiency.

The Process of Valve Shimming

The process of valve shimming may vary slightly depending on the engine’s design, but the general procedure remains the same. Let’s discuss the tools you’ll need and the steps involved.

Tools Required

To perform valve shimming, you’ll need the following tools:

  1. Feeler gauges for measuring valve clearances.
  2. A shim kit containing various shim sizes.
  3. A torque wrench for proper tightening.
  4. A valve cover gasket, if necessary.

Steps to Perform Valve Shimming

Removing the Valve Cover

First, remove the valve cover to access the engine’s valve train. This may require disconnecting various components, such as the ignition coil, spark plug wires, or hoses. Be sure to follow your vehicle’s service manual for specific instructions.

Measuring Valve Clearance

With the valve cover removed, rotate the engine until the camshaft lobes are facing away from the valves you’re measuring.

Using the feeler gauges, measure the gap between the camshaft or rocker arm and the valve stem. Record the clearance for each valve.

Selecting and Installing Shims

Based on the measured clearances, refer to the manufacturer’s specifications to determine the correct shim size.

Remove the existing shim and replace it with the appropriately sized shim. Ensure the new shim sits flush against the valve stem and camshaft or rocker arm.

Reassembling and Checking

Reassemble the engine components in reverse order of disassembly. Be sure to use a torque wrench to tighten bolts according to the manufacturer’s specifications.

Once reassembled, start the engine and let it warm up to operating temperature. Recheck the valve clearances to ensure they are within the specified range.

When to Shim Valves

Determining when to perform valve shimming depends on a few factors, including the signs of incorrect valve clearance and the manufacturer’s recommendations.

Signs of Incorrect Valve Clearance

Some symptoms that indicate it’s time to check and adjust valve clearances include:

  1. Excessive engine noise, particularly when the engine is cold.
  2. Reduced engine power and performance.
  3. Poor fuel efficiency.
  4. Difficulty starting the engine.

H2: Manufacturer’s Recommendations

It’s always best to follow the manufacturer’s recommendations for valve adjustment intervals. For most vehicles, this is typically around 15,000 to 30,000 miles, but it can vary depending on the engine type and usage.

Check your vehicle’s service manual for specific guidance.

Common Challenges and Tips

Valve shimming can be a complex procedure for those unfamiliar with engine maintenance. Here are some tips to help you overcome common challenges and achieve accurate results.

Ensuring Accurate Measurements

To obtain accurate valve clearance measurements, always:

  1. Use high-quality feeler gauges.
  2. Clean the gauges and contact surfaces before measuring.
  3. Hold the gauges perpendicular to the valve stem and camshaft or rocker arm.

Selecting the Right Shim Size

When selecting shim sizes:

  1. Always refer to the manufacturer’s specifications.
  2. Use the measured clearance to calculate the required shim size.
  3. Keep in mind that it’s better to err on the side of slightly larger clearances than too tight.

Avoiding Common Mistakes

To avoid common mistakes when shimming valves:

  1. Ensure the engine is cold before measuring clearances.
  2. Rotate the engine to the correct position for each valve.
  3. Double-check your measurements and shim selections before reassembling the engine.


Valve shimming is a critical maintenance procedure that helps ensure optimal engine performance and longevity.

By understanding the importance of valve clearance, following the proper procedure, and knowing when to perform this maintenance, you can keep your engine running smoothly and efficiently.


Can I perform valve shimming myself, or should I take my vehicle to a professional?

If you’re comfortable with engine maintenance and have the necessary tools, you can perform valve shimming yourself. However, if you’re inexperienced or unsure, it’s best to take your vehicle to a professional mechanic.

How often should I check my valve clearances?

Check your vehicle’s service manual for the manufacturer’s recommended valve clearance intervals. Generally, this ranges from 15,000 to 30,000 miles.

What happens if I don’t perform valve shimming?

Ignoring valve clearance maintenance can lead to reduced engine performance, poor fuel efficiency, increased noise, and potential engine damage.

Can I use any shims for valve shimming?

It’s essential to use shims specifically designed for your engine. Using incorrect shims can lead to improper valve clearance and possible engine damage.

Is valve shimming necessary for all engines?

Valve shimming is required for engines with adjustable valve clearances. Some modern engines use hydraulic valve lifters that don’t require adjustment.

Always consult your vehicle’s service manual to determine the maintenance requirements for your specific engine.

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