Valve Spring Service

After prolonged use, valve springs tend to weaken, lose tension, or even break. During engine service, always test valve springs to make sure they are usable.

Valve springs should be tested for uniformity and strength. The three characteristics to check are valve spring squareness, valve spring free height, and valve spring tension.

Valve spring squareness is easily checked with a combination square. Place each spring next to the square on a flat surface. Rotate the spring while checking for a gap between the side of the spring and the square. Replace any spring that is not square.

Valve spring free height can also be measured with a combination square or a valve spring tester. Simply measure the length of each spring in normal uncompressed condition. If it is too long or too short, replace the spring.

Valve spring tension, or pressure, is measured by using a spring tester. Compress the spring to specification height and read the scale on the tester.

Spring pressure must be within specifications. If the reading is too low, the spring has weakened and must be replaced.