Valve Seats, Reworking

WARNING: This page is about a different car, the 2023 Volkswagen Atlas. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Depth Gauge
Valve Seat Reworking Tool

Procedure

NOTE:

When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is also necessary to check the valve guides for wear. This is particularly important on high mileage engines. Refer to VALVE GUIDES, CHECKING .

Only reface valve seats enough until a perfect contact pattern is obtained. The maximum permissible reworking dimension must be calculated before work is carried out. If the reworking dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed and therefore the cylinder head should be replaced.

-- Remove the camshafts. Refer to CAMSHAFT, REMOVING AND INSTALLING .

The maximum permissible reworking dimension is calculated as follows:

-- Insert valve and press firmly against the valve seat.

NOTE:

If the valve is to be replaced as part of a repair, use a new valve for the measurement.

-- Measure the distance -a- between end of valve stem and upper edge of the cylinder head.

Fig 1: Identifying Distance Between End Of Valve Stem And Upper Edge Of Cylinder Head

Courtesy of AUDI OF AMERICA, LLC

-- Calculate the maximum permissible reworking dimension from measured distance -a- and minimum dimension.

Minimum dimensions:

Short intake valve	mm	31.8
Long intake valve	mm	10.2
Short exhaust valve	mm	31.8
Long exhaust valve	mm	10.2

Measured distance minus minimum dimension = maximum permissible reworking dimension.

Example:

	Measured distance	10.6	mm
-	Minimum dimension	10.2	mm
=	Maximum permitted reworking dimension	0.4	mm

Reworking the intake valve seat:

Fig 2: Identifying Angles And Dimensions To Rework Exhaust Valve Seat

Courtesy of AUDI OF AMERICA, LLC

= 32.8 mm diameter

= maximum permitted refacing dimension. Refer to ⁽¹⁾.

= 0.9 to 1.5 mm

= maximum diameter: 38.0 mm

r₂

= Radius 2.0 mm

= Cylinder head lower edge

= 45° valve seat angle

= 30° upper correction angle

= 60° lower correction angle

⁽¹⁾	How to calculate the maximum permissible refacing dimension. Refer to VALVE SEATS, REWORKING .

Reworking exhaust valve seat:

Fig 3: Identifying Angles And Dimensions To Rework Exhaust Valve Seat

Courtesy of AUDI OF AMERICA, LLC

= ø 29.8 mm

= maximum permitted refacing dimension. Refer to ⁽¹⁾.

= 1.2 to 1.7 mm

= 35.0 maximum diameter

r₂

= Radius 2.0 mm

= Cylinder head lower edge

= 45° valve seat angle

= 30° upper correction angle

= 60° lower correction angle

⁽¹⁾	How to calculate the maximum permissible refacing dimension. Refer to VALVE SEATS, REWORKING .