Engine timing, valves,  OM617

Machining valve seats



05—291 Machining valve seats




Valve seat width b
om617 - 0188-1.jpg
Valve seat angle a
Correction angle top /3
Correction angle bottom 7
Permissible runout of valve seat


Minimum distance “a” with new valves and new valve seats
om617 - 0188-2.jpg
+ 0.17 to-0.23
+ 0.12 to -0.28
Maximum distance “a” with new valves and machined (ref inished) valve seats




The max. distance is reduced by the same amount by which the cylinder head parting surface has been ref inished.


Valve stem wear (wear limit)


Special tools


Valve adjusting wrench 14 mm (2 each)
om617 - 0188-3.jpg
615 589 00 01 00
Holding wrench for valve spring retainer
615 589 00 03 00
Assembly mandrel for valve stem seals Intake and exhaust
617 589 00 43 00
Plug gage 10 mm dia. for intake and exhaust valve guide
615 589 00 21 00


05.8-291/1 F2




Conventional tools


Cylinder head clamping fixture
e.g. made by Christ, D-6801 Neckarhausen Order No. DBK 60-2


Valve seat machining tool
e.g. made by Hunger, D-8000 Miinchen Type VDNSL 1/45/30, order No. 236.03.308


Test kit for valve seats
e.g. made by Hunger, D-8000 Munchen Order No. 216.93.300


om617 - 0189-1.jpg
Clamp cylinder head into clamping fixture for disassembly and machin­ing.
Machine valve seats with valve machin­ing tool, with valve seat grinding machine or with valve seat milling cutter.


Machining valve seats


1 Check valve guides and replace, if required (05-285).
om617 - 0189-2.jpg


05.8-291/2 F2




2    Machine valve seat (30°) (refer to operating in­structions of tool manufacturer).
Release pilot (013) only after runout of valve seat has been checked.
3   Measure valve seat width b and correct below to 60°, if required.
If required, also correct clearance (/3) to 60°.
om617 - 0190-1.jpg


4 Check runout of valve seat.
om617 - 0190-2.jpg
For this purpose, slip test sleeve (017) with dial gage holder (016) and dial gage on pilot (013) and rotate test sleeve. The permissible runout of 0.03 mm should then not be exceeded.
013 Pilot
016    Dial gage holder
017    Test sleeve


5 Introduce new valve and measure max. distance a.
om617 - 0190-3.jpg


05.8-291/3 F2