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. 4.12 a).



3. Calculate the maximum allowable distance for lapping.

Minimum distance for inlet valve: 7.6 mm.

Minimum distance for exhaust valve: 7.6 mm.

4. Measured distance - minimum distance = maximum allowable lapping distance. For example, measured distance 8.0 mm - minimum distance 7.6 mm = maximum allowable lapping distance 0.4 mm.