Determining Maximum Allowable Reworking Dimension

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

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 refacing dimension is still 0 mm or less, replace cylinder head.

NOTE:

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

Refacing intake valve seat

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

Courtesy of AUDI OF AMERICA, LLC

a - Dia. 30.6 mm

b - Maximum permissible reworking dimension DETERMINING MAXIMUM ALLOWABLE REWORKING DIMENSION

c - 0.9 to 1.5 mm

d - Maximum dia. 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

Refacing exhaust valve seat

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

Courtesy of AUDI OF AMERICA, LLC

a - Dia. 26.7 mm

b - Maximum permissible reworking dimension DETERMINING MAXIMUM ALLOWABLE REWORKING DIMENSION

c - 1.2 to 1.7 mm

d - Maximum dia. 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