Valve Seats, Reworking

WARNING: This page is about a different car, the 2010 Audi Q7, 2009 Audi Q7, 2008 Audi Q7, and 2007 Audi Q7. However, it is still accessible from the selected car via links, so may be relevant.

If a perfect contact pattern is not achieved by grinding the valve seats, rework them.

NOTE:

If an engine with leaking valves is serviced, reworking or replacing valve seats and valves is not sufficient. The valve guides must be checked for wear, especially on engines with high mileage VALVE GUIDES, CHECKING .

Only rework valve seats enough to achieve a suitable contact pattern.

Calculate maximum permissible reworking dimension before reworking valve seats.

Special tools and workshop equipment required

Depth gauge
Valve seat reworking device

Maximum Refacing Dimension, Calculating

Proceed as follows:

NOTE:

If valve is replaced during repair, use new valve for measurement.

-- Insert valve and press firmly against seat.

-- Using depth gauge, measure distance -a- between end of valve stem and upper cylinder head surface.

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

Courtesy of AUDI OF AMERICA, LLC

-- Determine maximum allowable refacing dimension using distance measured and minimum dimension.

Measured distance minus minimum dimension = maximum permissible refaced dimension.

Intake Valve Minimum Dimensions		Exhaust Valve Minimum Dimensions
Short	Long	Short	Long
31.8 mm	10.2 mm	31.8 mm	10.2 mm

Example for long intake valve:
Measured distance		10.6 mm
Minimum dimension		- 10.2 mm
Maximum permissible reworking dimension		= 0.4 mm

-- If the maximum permissible refacing dimension is 0 mm or less, repeat measurement using new valve.

-- If maximum permissible reworking dimension is still 0 mm or less, replace cylinder head.

NOTE:

If reworking dimension is too small, hydraulic valve clearance compensation will not function properly.

Reworking Intake Valve Seat

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

Courtesy of AUDI OF AMERICA, LLC

a -

Diameter 30.6 mm

b -

Maximum permitted reworking dimension, refer to VALVE SEATS, REWORKING .

c -

0.9 to 1.5 mm

d -

Maximum diameter 35.0 mm

r2 -

Radius 2.0 mm

Z -

Cylinder head lower edge

α -

45° valve seat angle

β -

30° upper correction angle

γ -

60° lower correction angle

Reworking Exhaust Valve Seat

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

Courtesy of AUDI OF AMERICA, LLC

a -

Diameter 26.7 mm

b -

Maximum permitted reworking dimension, refer to VALVE SEATS, REWORKING .

c -

1.2 to 1.7 mm

d -

Maximum diameter 29.0 mm

r2 -

Radius 2.0 mm

Z -

Cylinder head lower edge

α -

45° valve seat angle

β -

30° upper correction angle

γ -

60° lower correction angle