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Valve & Valve Seat Servicing

CAUTION: DO NOT  reface exhaust valves on machine. Only lap in valves by hand.
  1. Valve seats must be refaced after replacement of guides. Damaged or burned seats may be refaced if correct seat width can be maintained. Upper angle (15° chamfer) cannot extend beyond perimeter of valve seat insert (where outer edge of seat meets cylinder head).
  2. First cut on valve seats is 45° angle. Stop refacing cut as soon as entire seat face is cleaned. Second cut is 75° angle to slightly chamfer lower edge of valve seats. Cut 15° angle at top of seat until correct seat width is obtained. Correct width for valve seats (45° face) is .055-.098" (1.4-2.5 mm).
  3. Dimensions of valves to be reused must be checked. On intake valves, head diameter is 1.575" (40.0 mm). Minimum stem diameter is .313-.314" (7.96-7.97 mm). Minimum length from stem tip to face is 4.823" (122.5 mm). Valve margin may NOT be less than .02" 5 mm). Margin is measured from upper (away from stem tip) edge of 45° to lower edge of chamfer around valve head.
  4. On exhaust valves, head diameter is 1.339" (34.0 mm). Minimum stem diameter is .3508-.3512" (8.91-8.92 mm). Minimum length from step tip to face is 4.823" (122.5 mm). No exhaust valve margin specification is given as manufacturer states that exhaust valves are NOT to be refaced by machine.
  5. Lap valves into seats by hand. Remove all lapping compound from valves and heads before reassembly. Excess grinding paste would cause rapid wear and internal damage to engine components. Leak test valves with solvent after valves and springs are reassembled in head.
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