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Calculating Maximum Permissible Machining Dimension Audi TT 8N

Cooling System (mechanical) 2 illustrations ~127 words
  1. Insert valve and press firmly against valve seat.

Note. If a valve has to be replaced as part of a repair, use the new valve for the measurement.

Scheme 184

Scheme 184
  1. Measure distance -a- between end of valve stem and upper cylinder head surface with a depth gauge.
  2. Calculate maximum permissible machining dimension using measured distance and minimum dimension.
Minimum dimension
Short intake valveLong intake valveShort exhaust valveLong exhaust valve
31.8 mm10.2 mm31.8 mm10.2 mm

Distance measured minus minimum dimension = maximum permissible machining dimension.

Example for outer intake valve
Distance measured10.6 mm
Minimum dimension10.2 mm
=Maximum allowable machining dimension= 0.4 mm

Note. If the maximum allowed machining dimension is 0 mm or less than 0 mm, repeat the measurement using new valve. If the measurement result is still 0 mm or less than 0 mm, replace the cylinder head.

Scheme 185

Scheme 185: Machining intake valve seat

Note. Calculating maximum permissible machining dimension. Refer to Calculating maximum permissible machining dimension .

DimensionIntake valve seat
A=Diameter 30.6 mm
B=Maximum permissible machining dimension
C=0.9...1.5 mm
D=Max. diameter 35.0 mm
R2=Radius 2.0 mm
Z=Bottom surface of cylinder head
Α=45° valve seat angle
Β=30° upper correction angle
Gamma=60° lower correction angle