Valve seat machining (VW Polo 3)

1. Insert the valve and press it firmly against the seat.

2. Measure the distance between the end of the valve stem and the top edge of the cylinder head (Fig. 4.25).



3. Calculate the maximum allowable distance for lapping.

• Minimum distance for inlet valve: 33.8 mm.
• Minimum distance for exhaust valve: 34.1 mm.

4. Measured distance - minimum distance = maximum allowable lapping distance. For example, Measured distance 35.1 mm - minimum distance 34.1 mm = maximum allowable lapping distance 1.0 mm.

The seat angles of the inlet valve are shown in Fig. 5.26, and the outlet valve - in Fig. 5.27.

Intake valve seat angles

Diameter a: engines 1F and ADZ - 37.2 mm; aFT engine - 39.2 mm
Diameter b: maximum allowable distance for lapping.
c = max 2.0 mm.
Z = Lower edge of cylinder head.
Valve seat angle α = 45°.
Upper correction angle β = 30°.
Lower correction angle γ = 60°.

Exhaust valve seat angles

Diameter a = 32.4 mm.
Diameter b: maximum allowable distance for lapping.
c = max 2.0 mm.
Z = Lower edge of cylinder head.
Valve seat angle α = 45°.
Upper correction angle β = 30°.
Lower correction angle γ = 60°.