How to Check a Valve Spring

You should check the valve spring in your car when you are going for a cylinder head overhaul. If there are any worn out springs, they can damage the valve stems and guides quickly. The springs will likely be excessively compressed after several years of use, and this can cause valves to clatter, placing limits on the RPM of your engine. In more extreme cases, this can also lead to valve train damage. A few simple tests will allow you to determine whether it is necessary to replace the spring valves when you are carrying out a cylinder head overhaul.

Tools and Materials Needed:

  • Combination Square
  • Feeler Gauge
  • Straightedge
  • Vernier Caliper
  • Spring Load Tester
  • Vise

Step 1 – Check that the Spring is Loading Retainers Evenly

To determine whether the spring is loading the retainers evenly, check the valve spring to make sure that it has an even surface. Place the spring on a flat surface and use a combination square against it, rotating the spring as you monitor the gaps around it. Use the gauge to measure any gaps. If the gap is more than a sixteenth of an inch, then the spring will need replacing. Check the rest of the valve springs in the same manner.

Step 2 – Inspect the Free Height of the Valve Springs

Inspect the free height of the springs. This will allow you to determine whether or not any of the springs has been adversely affected by the high temperatures of the engine, increasing its normal height to a level where it is no longer effective. Remove the springs and line them up beside each other, making sure that you are working with a completely flat surface. Use a straightedge by placing it on top of the springs, and measure the gaps between the straight edge and the top of the spring using the gauge. If you find that the height of the springs varies by more than a sixteenth of an inch compared to the others, then they will need replacing.

Step 3 – Measure the Spring Free Height

A vernier caliper is the tool that you’ll use here to measure the free height of the springs, comparing them with the specifications provided by the service manual for your car. Typically, a variation of the sixteenth of an inch is within reasonable limits, although if you are going to be using your car in heavy traffic a great deal or use a trailer, this will not be optimal.

Step 4 – Measure the Load Producing Capacity of the Springs

When you compress the springs to a certain height, the valve spring should have the strength to easily carry a proportional load. You can measure this characteristic by compressing the spring using a spring load tester, a tool specifically designed for the job. Using a vise, compress the spring to the installed height which is specified in the service manual for your car. The load capacity should typically be between 76 and 84 pounds.