TM 9-2815-237-34 2-21. CYLINDER HEAD AND VALVE REPAIR  (Cont’d) b.  Cleaning 1. Using bench grinder and rotary wheel wire brush, clean all valve stems (2) and valve heads (3). 2. Using drill motor and rotary end wire brush, clean all combustion chambers ( 12) and intake and exhaust  ports  (13). 3.  Refer  to  para.  2-9  for  additional  cleaning  information. 4.  Repeat  steps  1  through  3  for  opposite  cylinder  head. c.  Inspection 1. 2. 3. 4. 5. 6. 7. 8. NOTE For  general  inspection  instructions,  refer  to  para.  2-10. Inspect  valves  (1)  for  cracks,  scoring,  galling,  and  burned  heads  (3).  Replace  valves  (1)  if  cracked, scored,  galled,  or  if  heads  (3)  are  burned. Inspect  valve  springs  (8)  and  dampers  (7)  for  damage.  Replace  valve  spring  (8)  if  either  are damaged. Inspect valve caps (5), shields (6), valve spring shims (9), and valve keys (4) for damage. Replace if  damaged. Remove dampers (7) from valve springs (8). Using valve spring tester, compress valve spring (8) to  1-13/16  in.  (46  mm).  If  pressure  is  less  than  70  lb  (311  N),  replace  valve  spring  (8).  Compress valve spring (8) to 1-25/64 in. (35 mm). If pressure is less than 220 lb (978 N), replace valve spring (8). Test remaining springs in same manner. Install dampers (7) into springs (8). Inspect cylinder head (11) for cracks in valve ports (13) or combustion chambers (12) and external cracks  to  the  coolant  chamber  (14).  Replace  cylinder  head  (11)  if  cracked. NOTE Precombustion  chamber  is  available  in  standard  and  oversize. If replacing a precombustion chamber, check for marking "OS” on  precombustion  chamber.  If  marking  is  present,  oversize  pre- combustion  chamber  must  be  used. Inspect  precombustion  chambers  (10)  for  cracks  or  damage.  Replace  if  cracked  or  damaged. Inspect cylinder head (11) mating surfaces for scratches or dents. Replace cylinder head (11) if scratched  or  dented  deeper  than  0.003  in.  (0.076  mm). Using  a  straight  edge  and  feeler  gauge,  check  flatness  of  cylinder  head  to  block  mating  surface. Flatness  of  cylinder  head  (11)  must  not  vary  more  than  0.002-in.  (0.051  mm)  in  distance  of  6  in. (15.2 cm), or more than 0.006 in. (0.152 mm) overall. Replace cylinder head (11) if flatness does not meet   specifications. 2-64