A8 Sedan V8-3.7L (AEW) (1997)
Valve Seat: Service and Repair
NOTE:
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Pay affection the cylinder head minimum dimension when refacing valve seats.
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Only reface valve seats enough to produce perfect contact.
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Before refacing, calculate the maximum permissible refacing dimension. If this dimension is exceeded, correct functioning of hydraulic valve
lifters can no longer be guaranteed and the cylinder head must be replaced.
Maximum Permissible Refacing Dimension, Calculating
1. Insert valve into guide and press firmly against valve seat.
2. Measure distance (arrow) between end of valve stem and top surface of cylinder head.
3. The maximum permissible refacing dimension is the difference between the actual distance measured at the cylinder head and the specified
minimum dimension.
Minimum dimensions
At intake valve: 36.4 mm (1.433 inch).
At exhaust valve: 36.4 mm (1.433 inch).
Refacing Intake Valve Seat
a - Diameter: 31.9 mm (1.255 inch).
b - Seat width: 1.5-1.8 mm (0.059-0.071 inch).
Correction angle: 75°.
Valve seat angle: 45°.
Z - Bottom surface of cylinder head.
Refacing Exhaust Valve Seat
a - Diameter: 26.0 mm (1.024 inch).
b - Seat width: 1.5-1.8 mm (0.059-0.071 inch).
Correction angle: 75°.
Valve seat angle: 45°.
Z - Bottom surface of cylinder head