TM 10-3930-653-14&P is less than 0.5 mm (0.020 in).  Do not grind end of stem (valve) more than 0.5 mm (0.020 in) [keep within 0.5 mm (0.020 in)]. Unit: m (mm) Fig. 4-44.  Dimension of Intake Valve Unit: mm (in) Fig. 4-45.  Dimension of Exhaust Valve 4-2-4-5. VALVE SPRINGS (1)   Inspect  springs    for  cracks    or    damage,  measure spring   force,   and   replace   if   damaged   or   not   within prescribed limits. (2)   Measure  inclination  (right  angle  align-ment)  of  each valve  spring  with  a  try  square  (back  square).    Replace springs if inclined by more than limit. Fig. 4-46.  Measuring Spring Inclination Valve spring specification Model H20 Item Free length mm (in) 49.0 (1.929) Installed (set) length 390 (1.535) mm (in) Set load kg (lb) 30 (66) Inclination limits Less than mm (in) 1.5 (0.059) Fig. 4-47.  Measuring Spring Constant 4 - 30