Replacing Valve Guides

4. Loosen valve guides from camshaft end with brief hammer knocks on Special Tool 9224 and press out rest of guides toward combustion side with a press.

1. Clean and inspect cylinder head. Cylinder heads are not suitable for replacement of valve guides, if their valve seats and sealing surfaces can no longer be machined.

2. Machine off protruding valve guides from the camshaft side with a countersink, Special Tool 9220/1, until guides are flush with the cylinder head.

Note:

Be careful not to damage guide collar for spring retainers.

5. Check bores in cylinder head with an internal gauge.

3. Place cylinder head on Special Tool 9220.

4. Loosen valve guides from camshaft end with brief hammer knocks on Special Tool 9224 and press out rest of guides toward combustion side with a press.

Note:

If pertinent workshop equipment is available, valve guides can be chilled in liquid air and pressed into a cylinder head heated to 190 °C/375 DF. Cylinder head may be kept at temperature of 190 °C/375 °F for max. 90 minutes.

8. Ream out valve guides to size 9.00 - 9.015 (9 H 7) with a reamer.

6. Grind off service valve guide, Part No. 928 104 328 52 (13.27 mm outside dia.}, accordingly.

Press-fit for intake and exhaust valve guides must be 0.06 to 0.08 mm.

Example:

Measured bore diameter in cylinder head = 13.01 mm. Outside diameter of service valve guide ground accordingly to 13.07 . . . 13.09 mm.

7. Coat valve guides with tallow, insert with a light knock, align and press into cylinder head against stop from camshaft side with Special Tool 9221.

9, If absolutely necessary, valve guides can be reamed out with Special Tool 3015.

Procedures:

Always ream out valve guides with "petroleum" as a lubricant. Back out reamer frequently to remove burrs. Check reamed bore with limit gauge P 206 and, if necessary, ream out bore again with a dry reamer.

10. Valve seat inserts must be machined after replacing valve guides. Grinding in valves with grinding paste will not be sufficient.

CHECKING TDC MARKS ON CAMSHAFT SPROCKETS (Do not remove toothed belt cover)

'86 MODELS ONWARD

ENGINE TYPE M 28. 21/22

The covers fitted as of model year "86 have cast noses at the air-bleed ports for the intake hoses; with the crankshaft at the ignition TDC for cylinder no.l, these noses must be aligned with the recesses in the camshaft sprockets.

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