Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI1998A8 SEDAN (4D2) V8-3.7L (AEW)REPAIR AND DIAGNOSISSPECIFICATIONSMECHANICAL SPECIFICATIONSENGINECYLINDER HEAD ASSEMBLYVALVE SEAT
1998 Audi A8 Sedan (4D2) V8-3.7L (AEW)
Valve Seat
1998 Audi A8 Sedan (4D2) V8-3.7L (AEW)SECTION Valve Seat
MINIMUM VALVE STEM DEPTH
Measure distance (arrow) between end of valve stem and top surface of cylinder head.
Minimum dimensions:
At intake valve: 36.4 mm (1.433 inch).
At exhaust valve: 36.4 mm (1.433 inch).
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.
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
Measure distance (arrow) between end of valve stem and top surface of cylinder head.
Minimum dimensions:
At intake valve: 36.4 mm (1.433 inch).
At exhaust valve: 36.4 mm (1.433 inch).
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.
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
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.