Workshop Manual

009W2329-R01
C19
Replacement of valve seats
The valve seat rings should be replaced when, after repeated millings and grindings, they
have been milled so far down that the valv e heads are more than 0.3 mm belo w the face of
joint of the cylinder head (see the sketch below).
1. Remove the valve springs an d valves as indicated previously in this section.
2. Place a lead plate or an annealed copper plate between the cylinder head and a bent
chisel and knock out the valve s eat ring with this (crowbar princ iple) by sticking one
end of the chisel under the rear edge of the valve seat ring.
IT IS IMPORTANT THAT THE FILLING PIECE IS USED BETWEEN CYLINDER HEAD
AND CHISEL IN ORDER TO AVOID DAMAGING THE CYLINDER HEAD.
Before fitting new valve seat rings, clean the bores in the cylinder head for same and check
that the holes are not oval.
Then warm up the cylinder head in hot water to about 100° C (212° F), after which fit, by
means of a punch, the valve seat rings having been cooled down beforehand in nitrogen or
carbon dioxide.
When fitting the valve seat rings, the difference of temperature between cylinder head and
valve seat ring is to be 220 – 250° C (430 – 480° F).
DO NOT KNOCK IN THE VALVE SEAT RING VIOLENTLY. ONLY ACTIVATE THE
PUNCH WITH A RATHER GENTLE BLOW IN ORDER TO FIT THE VALVE SEAT RING.