SEAT Workshop Service and Repair Manuals

Valve seats: reworking Special tools and workshop equipment required t  Depth gauge t  Valve seat re-facing tool   Note t  If there is not achieved a good seating pattern by lapping the valve seats, the valve seats must be reworked t  When repairing engines with leaking valves, it is not sufficient to reface the valve seats and renew the valves. The valve guides must also be checked for wear. This is particularly important on high mileage engines → Chapter. t  The valve seats should only be reworked just enough to produce a good seating pattern. t  Before re-facing, the max. allowable re-facing value must be calculated. t  If the reworking dimension is exceeded, hydraulic valve compensation can no longer be guaranteed and the cylinder head should be renewed.

Maximum permissible reworking dimension: calculation –  Insert valve and press firmly against valve seat.   Note If the valve is to be renewed as part of a repair, use a new valve for the calculation. –  Use a depth gauge to measure distance -a- between end of valve stem (upper edge) and top surface of cylinder head. –  Calculate maximum permissible reworking dimension from measured distance and minimum dimension. l  Minimum dimension for intake and exhaust valve: 31.2 mm. Measured distance minus minimum dimension = max. permissible reworking dimension.

Minimum measurement for the intake valve:
	Measured distance-a-		31.5 mm
-	Minimum dimension		- 31.2 mm
=	Max. permissible machining dimension		= 0.3 mm

Note If the maximum permissible reworking dimension is 0 mm or less than 0 mm, repeat the measurement with a new valve. If the measured result is again 0 mm or less, renew the cylinder head.

Inlet valve seats: Supplementary work

Inlet valve seat:
a	=	Ø 39.2 mm
b	=	Max. permissible machining dimension
c	=	1.8 ... 2.2 mm
Z	=	Lower edge of cylinder head
45°	=	Valve seating angle
30°	=	upper correction angle

Note Calculating max. permissible reworking dimension → Anchor.

Exhaust valve seats: Supplementary work

Exhaust valve seat:
a	=	Ø 32.4 mm
b	=	Max. permissible machining dimension
c	=	2.2 ... 2.6 mm
Z	=	Lower edge of cylinder head
45°	=	Valve seating angle
30°	=	upper correction angle

Note t  Calculating max. permissible reworking dimension → Anchor. t  Exhaust valve seat inserts have additionally a restriction. When reworking observe that the radius of the restriction is not damaged.