How to Measure Valve Spring Installed Height (Step-by-Step Guide)

Measuring valve spring installed height is one of the most important steps when setting up a valvetrain. Even a small change in installed height can significantly affect seat pressure, open pressure, and overall valve control.

If you're unsure what pressure your setup should have, check out our Valve Spring Pressure Chart & Guide or use our Valve Spring Calculator to estimate your numbers.

What Is Valve Spring Installed Height?

Installed height is the distance from the spring seat (on the cylinder head) to the underside of the retainer when the valve is fully closed and the locks are installed.

This measurement determines how much preload is on the spring at rest, which directly affects seat pressure and open pressure.

Why Installed Height Matters

• Controls seat pressure at closed valve position
• Determines open pressure at max lift
• Affects valve control at higher RPM
• Prevents coil bind and component damage
• Ensures proper valvetrain stability

Even a change of .010" in installed height can noticeably affect spring pressure, which is why accuracy matters.

Tools Needed to Measure Installed Height

• Installed height mic (recommended)
• Valve spring shims
• Retainers and locks (final parts you will use)
• Calipers (optional for verification)

Step-by-Step: How to Measure Installed Height

Step 1: Install the Valve

Insert the valve into the guide as it will be assembled. Make sure the valve is fully seated.

Step 2: Install Retainer and Locks

Install the exact retainer and locks you plan to run. These components affect installed height and must match your final setup.

Step 3: Insert Installed Height Mic

Place the installed height mic in the spring location between the seat and the retainer.

Step 4: Expand the Mic

Expand the mic until it fits snugly between the spring seat and the underside of the retainer. Do not over-tighten — you want a firm but accurate measurement.

Step 5: Read the Measurement

The reading on the mic is your installed height. Record this measurement for each valve location.

Adjusting Installed Height

If your installed height does not match the target specification, you can adjust it using shims.

• Add shims to reduce installed height (increase pressure)
• Remove shims to increase installed height (reduce pressure)

Always verify your final measurement after making adjustments.

Common Mistakes When Measuring Installed Height

• Using the wrong retainers or locks
• Not measuring each valve location individually
• Forgetting to account for valve job changes
• Not verifying measurements after shimming
• Assuming all cylinders are identical

Installed Height and Spring Pressure

Installed height directly affects spring pressure. A shorter installed height increases pressure, while a taller installed height decreases pressure.

To calculate how your installed height affects pressure, use our Valve Spring Calculator.

Final Checks Before Assembly

• Verify installed height on every valve
• Check seat and open pressure
• Confirm coil bind clearance
• Check retainer-to-seal clearance
• Confirm compatibility with camshaft specs

Need Help With Your Valve Spring Setup?

Fastime Performance can help you dial in your valve spring setup, installed height, and valvetrain combination. If you're unsure about your measurements or spring selection, reach out and we can help verify your setup.