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Maximum Permissible Refacing Dimension, Calculating Audi A8 D3

Mechanical 1 illustration ~110 words
  1. Install valve and press it firmly onto the valve seat. NOTE: If you intend to replace the valve, use new valve for measurement.
  2. Install valve and press firmly against valve seat.
  3. Measure distance between end of valve stem and top surface of cylinder head.
  4. Calculate maximum permissible refacing dimension from measured distance and minimum dimension.
Outer intake valveCenter intake valveExhaust valve
34.0 mm (1.338 in.)33.7 mm (1.326 in.)34.4 mm (1.354 in.)

MINIMUM DIMENSIONS

The measured distance minus the minimum dimension equals the maximum permissible refacing dimension.

Outer intake valve
Measured dimension34.4 mm (1.354 in.)
Minimum dimension34.0mm (1.338 in.)
Maximum permissible refacing= 0.4 mm (0.0157 in.)

MAXIMUM PERMISSIBLE REFACING DIMENSION (EXAMPLE)

Note. If the measured distance is less than the minimum dimension, repeat the measurement with new valves or replace the cylinder head.

Scheme 170

Scheme 170
  1. Valve seats, refacing
Intake valve seat
A = 26.2 mm (1.0314 in.) diameter
B = 1.5 to 1.8 mm (0.059 to 0.070)
Z = Lower cylinder head surface
Alpha = 45° Valve seat angle
Beta = 30° Upper correction angle
Gama = 60° Lower correction angle
Exhaust valve seat
A = 29.0 mm (1.114 in.) diameter
B = approx. 1.8 mm (0.070)
Z = Lower cylinder head surface
Alpha = 45° Valve seat angle
Beta = 30° Upper correction angle
Gama = 60° Lower correction angle

VALVE SEAT SPECIFICATIONS