TM 10-3930-653-14&P Fig.  4-8. Checking Ignition Timing Adjust the timing to specifications, by turning distributor body after loosening the securing bolt. Fig.  4-9. Adjusting Ignition Timing Ignition timing (B.T.D.C./rpm): 8°/650...  H20PU240 (4) CHECKING OR REPLACING SPARK  PLUGS Fig.  4-10.  Checking Spark Plug Gap. 1.  See that correct spark plugs are used.  Spark plug insulators should be thoroughly cleaned to prevent possible flash-over. 2.  Thoroughly clean lower insulator and cavity by blast type cleaner.  File both electrodes flat (rounded surfaces increase voltage required to fire plugs) and set gap.  Tighten plugs to specified torque. (5)    CHECKING   AND   CLEANING   HIGH   TENSION   WIRES, DISTRIBUTOR CAP AND ROTOR WARNING Dry  cleaning  solvent  P-D-6XO  is  toxic  and  flammable.    Wear protective  goggles  and  gloves  and  use  only  in  a  well  ventilated area Avoid contact with skin, eyes, and clothes and don't breathe vapors.    Do  not  use  near  open  flame  or  excessive  heat    If  you become    dizzy    while    cleaning    with    solvent,    get    fresh    air immediately land get medical aid.  If contact with skin or clothing is  made,  flush  with  water.    If  contact  with  eyes  is  made,  slash sour eyes with water and get medical aid immediately. External   surfaces   of   all   parts   of   secondary   system   must   be cleaned  to  reduce  possibility  of  voltage  loss.    All  wires  should  be removed   from   distributor   cap   and   coil   so   that   terminals   can   be inspected  and  cleaned.    Burned  or  corroded  terminals  indicate  that wires were not fully seated, which causes arcing between end of wire and terminal.  When replacing wires in terminal, be sure they are fully seated   before   pushing   rubber   nipple   down   over   tower.      Check distributor rotor for damage, and distributor cap for cracks. (6)    GREASING DISTRIBUTOR SHAFT AND CAM HEEL Clean and apply multi-purpose grease to cam and wick. Note: Do not apply grease excessively. 4-1-3-4. AIR CLEANER FILTER (DRY TYPE) WARNING Compressed air used for cleaning purposes will not exceed 30 PSI.  Use only with effective hip guarding and personal protective equipment (goggles/shield, gloves, etc.). It is necessary to clean the element or replace it at the recommended interval, more often under dusty driving conditions. Fig.  4-11. Replacing Air Cleaner Filter 4 - 12