Valve seats, refacing

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CAUTION: When refacing valve seats, remove only enough material to produce the correct seat contact pattern. The maximum permissible refacing dimension must be calculated before refacing.
If the maximum refacing dimension is exceeded, the hydraulic lifters will not function properly and the cylinder head must be replaced.

Calculating maximum permissible reworking dimension

Insert valve and push firmly against valve seat.
Measure distance -a- between center of valve stem and upper edge of cylinder head.

Measured distance minus the minimum dimension is the maximum permissible refacing dimension.

Fig 1: Measuring Distance -a- Between Center Of Valve Stem And Upper Edge Of Cylinder Head

Courtesy of VOLKSWAGEN OF AMERICA, INC.

Minimum dimensions:

Intake valve: 33.8 mm (1.330 in.)
Exhaust valve: 34.1 mm (1.342 in.)

Minimum Dimension Example:

Measured distance -a-: 35.1 mm

- Minimum dimension: 33.8 mm

= Max. permissible refacing dimension: 1.3 mm

NOTE: If the measured distance -a- is smaller than the minimum dimension, measure again with new valves. If necessary, use shorter valves (CAMSHAFT IDENTIFICATION AND TIMING , valve length -c-) or replace cylinder head.

Intake valve seat, refacing

a = 39.2 mm (1.543 in.)

b = max. permissible reworking dimension

c = approx. 2.0 mm (0.079 in.)

Z = cylinder head lower edge

30° = correction angle, upper

45° = valve seat angle

Fig 2: Identifying Intake Valve Seat Dimensions

Courtesy of VOLKSWAGEN OF AMERICA, INC.

Exhaust valve seat, refacing

a = 32.4 mm (1.276 in.)

b = max. permissible reworking dimension

c = approx. 2.4 mm (0.094 in.)

Z = cylinder head lower edge

30° = upper correction angle

45° = valve seat angle

CAUTION: Exhaust valve seat rings are provided with a neck. During reworking, make absolutely sure that the radius of the neck is not damaged.

Fig 3: Identifying Exhaust Valve Seat Dimensions

Courtesy of VOLKSWAGEN OF AMERICA, INC.