Place the spring on a flat surface next to a square. Measure the height of the spring, and rotate it against the edge of the square to measure distortion. If spring height varies (by comparison) by more than 1⁄16 in. (1.6mm) or if distortion exceeds 1⁄16 in. (1.6mm) replace the spring. In addition to evaluating the spring as above, test the spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester.
| Fig. 1: Check the valve spring for squareness on a flat surface, a carpenters square can be used |