Machining valve seats

Note

Before refacing the valve seats, check dimension "A" to avoid carrying out work that may be unnecessary if the wear limit has been exceeded.

Valve seats may be machined down to the wear limit "A" = 14,5 mm (size new 13.65 ± 0.45).

Check with a new valve. Distance "A" must not be exceeded, as otherwise the function of the hydraulic valve tappet would not be assured.

Remove no more than the absolute minimum amount of metal in order to prevent premature wear.

Checking valve guides

1. Remove deposits with a cleaning reamer.

2. Place new valve in valve guide and check that valve stem end is flush with cylinder head/camshaft housing mating face.

Intake Valve Porsche 928

3. Check clearance with dial gage holder VW 387 and dial gage. Wear limit = 0.80 mm.

Machining valve seats, checking valve guides

Printed in Germany - XXVII, 1991

Intake valve Exhaust valve

Checking Installed Length of Valve Springs

1. Install Special Tool 9138 with shims belonging to a pertinent valve, spring retainer and both keepers.

2, Read distance from Special Tool 9138 and, if necessary, correct by adding or removing shims. Shims are available in thicknesses of 0.5 and

928 Models 1978/1979

Intake valve Exhaust valve

928 Models 1980

Intake valve Exhaust valve

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