Skoda Workshop Service and Repair Manuals

Reworking valve seats Special tools and workshop equipment required t  Universal dial gauge holder -MP3-447 (VW 387)- t  Dial gauge t  Micrometer or caliper gauge t  NAC milling cutter for reworking valve seats t  Grinding paste   Note t  When carrying out repairs on engines with leaking valves, it is not sufficient to machine or replace the valve seats and valves. It is also necessary to inspect the valve guides for wear, particularly on engines with a high mileage → Chapter. If the wear limit is exceed, replace cylinder head. t  Calculate the maximum permissible reworking dimension before commencing → Anchor. If the reworking dimension is exceeded, proper operation of the valve gear is no longer assured and the cylinder head must be replaced. t  Do not remill valves. Only opposite grinding in of the valve with the corresponding valve seat using grinding paste is permissible, in order to obtain a proper contact pattern. Calculating maximum permissible reworking dimension –  Insert valve and press firmly against the valve seat.   Note t  If the valve is replaced when carrying out repair work, use a new valve for the measurement. t  If no new valve is used, then the valve disc must be thoroughly cleaned. For engines with identification characters BBM, CHFA

–  Attach universal dial gauge holder with bolt to cylinder head.

–  Measure distance -h- from the bottom edge of the cylinder head to the bottom edge of the valve disc. Measure in the immediate vicinity of the recess from the valve disc center -arrows-.

–  Measure valve length -c-.   Note Measure dimension -c- in the immediate vicinity of the recess from the valve disc center. –  Calculate max. permissible reworking dimension from the distances -c, h- measured and from the maximum dimension. Maximum dimension for both valves: 103.7 mm The maximum permissible reworking dimension = 103.7 - (c + h). Example:

	Maximum dimension for both valves	103,7	mm
-	(Valve length -c- + measured distance -h-)	(99,2 + 4,35)	mm
=	max. permissible reworking dimension 1)	0,15	mm

1) The maximum permissible reworking dimension is shown in the figures for reworking the valve seats as dimension „b“. For engines with identification characters BME, BZG, CGPA, CGPB, CEVA, CJLA

–  Measure distance between the valve stem end and the upper face of the cylinder head. –  Calculate max. permissible reworking dimension from the distance measured and the minimum dimension.

Minimum dimension: for inlet and exhaust valve	7.6 mm

„Measured distance“ - „minimum dimension“ = „max. permissible reworking dimension“. Example:

Measured distance	8.0 mm
- Minimum dimension	7.6 mm
= max. permissible reworking dimension 1)	0.4 mm

1) The max. permissible reworking dimension is shown in the figures for reworking the valve seats as dimension „b“. Continued for all engines   Note If the max. permissible reworking dimension is 0 mm, if necessary repeat measurement with a new valve. If the max. permissible reworking dimension is again 0 mm, replace cylinder head.