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====== IH: Engine Mechanicals - Sub-03E ======
====== Three angle valve seats - FLT/FL/FX/XL models ======


  * The MoCo issued a bulletin in June of 1980 stating that all 1980 production models incorporate three angle valve seats on the (intake and exhaust) ports on the new -80 heads. ((HD Service Bulletin #M-782 dated June 3, 1980)) 
  * In April of 1981, this was reiterated for XL Models starting with crankcase (781012001) with the introduction of new heads for the 81 model year, ((HD Service Bulletin #M-827 dated April 24, 1981)) which were available as replacement for previous year models. 
  * There are specific procedures that must be followed when cutting this type of valve seat. Always be sure to reface the valves before you cut the seats. A Neway Valve Seat Cutter (444-HDF) or other quality equipment is recommended for this.  
  * Follow the procedures outlined in the service manual for removing and re-facing valves and guides and decarbonizing the combustion chamber.
    - Cut the 46° seat angle first.  Cut only enough to clean up the seat.
    - Apply bluing to the valve and install the valve in the head. Rotate the valve against seat. Remove the valve and check the contact pattern. The valve seat should be 1/16” wide and centered on the valve.
    - If the valve seat pattern is too close to the stem side of the valve face, cut a 60° angle to raise the seat. If the pattern is too close to the edge of the valve face, cut a 31 ° angle to lower seat.
    - After cutting the 31° and / or 60° angles to position the seat, final cut the 46° seat angle to obtain the proper 1/16” width.
    - Recheck the valve seat width and location with bluing as described in Step 1.
    - When reassembling, follow the inspection and assembly instructions found in the 1980 service manuals to insure the proper valve seat height, valve guide installation and valve spring length / tension.


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