Feature SPEC: The 66834 mini valve spring tester has a wider range of 0-700 with 10-pound increments. Double scale measuring units are easy to read, measuring range is 0-700 psi / 0-50 kg-cm2. FUNCTION: The 66834 mini valve spring tester are an affordable and portable way to test springs. Racer need to know what a valve spring’s pressure, or rate, is both at assembly and after use. Coil springs will wear out and lose pressure with use, so racers need to periodically check spring rate to make sure that they’re up to the job after a few races. Also, sometimes a performance drop-off can be caused by worn out springs, leading a racer to check them. .