The are two different types of valve springs used that are interchangable, but have different specifications(Refer to 9 - ENGINE/CYLINDER HEAD/VALVE SPRINGS - DESCRIPTION). Whenever valves have been removed for inspection, reconditioning or replacement, valve springs should be tested . As an example; the compression length of a spring to be tested is 38.00 mm (1.496 in.). Turn the table of Tool C-647 until surface is in line with the 38.00 mm (1.496 in.) mark on the threaded stud and the zero mark on the front. Place spring over stud on the table and lift compressing lever to set tone device. Pull on torque wrench until ping is heard. Take reading on torque wrench at this instant. Multiply this reading by two. This will give the spring load at test length. Fractional measurements are indicated on the table for finer adjustments. Refer to Engine Specifications to obtain specified height and allowable tensions (Refer to 9 - ENGINE - SPECIFICATIONS). Replace any springs that do not meet specifications.