Standard Procedure - Valve And Valve Seat Refacing

Fig 1: Intake and Exhaust Valve Refacing

Courtesy of DAIMLERCHRYSLER CORP.

For all applicable valve and seat dimensions and angles (Refer to ENGINE - SPECIFICATIONS)  .

1. Reface valves using a suitable valve refacing machine.
2. Inspect the remaining margin (2) after the valves are refaced. See Fig 1. Intake valves with less than 0.79 mm (0.0312 in.) margin and exhaust valves with less than 1.19 mm (0.0469 in.) margin should be replaced.
   Fig 2: Valve Face and Seat

   Courtesy of DAIMLERCHRYSLER CORP.

   1 - SEAT WIDTH

   2 - FACE ANGLE

   3 - SEAT ANGLE

   4 - SEAT CONTACT AREA

3. Valve seats which are worn or burned can be reworked, provided that correct angle and seat width are maintained. Otherwise the cylinder head must be replaced.
4. Reface valve seats (3) using a suitable valve seat machine.
5. When refacing valve seats (3), it is important that the correct size valve guide pilot be used for reseating stones or cutter. A true and complete surface must be obtained.
   Fig 3: VALVE SEAT CONCENTRICITY

   Courtesy of DAIMLERCHRYSLER CORP.
6. Measure the concentricity of valve seat (3) and valve guide using a valve seat runout dial indicator (4). Total runout should not exceed. 0.051 mm (0.002 in.) (total indicator reading).
7. Inspect the valve seat with Prussian blue to determine where the valve contacts the seat. To do this, coat valve seat LIGHTLY  with Prussian blue then set valve in place. Rotate the valve with light pressure. If the blue is transferred to the center of valve face, contact is satisfactory. If the blue is transferred to top edge of the valve face, lower valve seat with a 15 degrees stone/cutter. If the blue is transferred to the bottom edge of valve face raise valve seat with a 65 degrees stone/cutter.
8. When seat is properly positioned the width of intake and exhaust seats should be 0.75-1.25 mm (0.029-0.049 in.).
   Fig 4: Checking Valve Tip Height and Valve Spring Installed Height

   Courtesy of DAIMLERCHRYSLER CORP.
9. Check valve tip to cylinder head surface dimensions (5) after machining the valve seats or faces. Grind valve tip until within specifications. Measure from valve tip to cylinder head surface when valve is installed in the head (5). See Fig 4. For valve tip specifications, (Refer to ENGINE - SPECIFICATIONS)  . The valve tip chamfer is needed to be reground to prevent seal damage when the valve is installed.
10. Measure valve spring installed height (4). See Fig 4. Measure from the top of the valve spring seat/seal to the bottom of the valve spring retainer. For valve spring installed height specifications, (Refer to ENGINE - SPECIFICATIONS)  .