TM 10-3930-659-34 4-6. CYLINDER HEAD ASSEMBLY REPAIR (Con’t). WARNING Prussian blue dye is poisonous and can burn skin on contact. Always wear protective goggles and gloves, and use only in a well-ventilated area.  Overexposure  to  Prussian  blue  dye  can  cause  serious  heart  and skin problems, dizziness, and unconsciousness if not handled properly. 16. Remove  cylinder  head  valve  (5)  from  cylinder  head  (4)  and  apply  a  thin  coat  of  Prussian  blue  dye  to  face  of cylinder head valve. 17. Position cylinder head valve (5) in cylinder head (4) and turn cylinder head valve one complete revolution. Remove cylinder head valve from cylinder head. 18. Inspect cylinder head valve (5) for low spots or evidence of poor contact between cylinder head valve and cylinder head (4). Low spots will be free of Prussian blue dye. NOTE Perform step 19 only if cylinder head valve has low spots or poor contact with cylinder head. 19. Using valve face grinding machine, grind cylinder head   valve   (5)   as   necessary.   Intake   cylinder head   valve   must   be   ground   to   an   angle   of 29.50°.  Exhaust  cylinder   head   valve   must   be ground to an angle of 43.5°. 20.    Repeat  steps  16  through  18.  If  cylinder  head valve still will not seat, replace valve seats insert (see step 7). c. ASSEMBLY 1.    If   removed,   install   valve   seat   insert   (10)   in cylinder head (4). 4-25