Checking Dimensions

NOTE:
^ Numbers in parentheses ( ) indicate a component or tool in the associated illustration.
^ Minor differences in the flatness in the longitudinal direction should not be reworked as these even themselves out when the cylinder head is tightened.

PROCEDURE
- Valves and prechambers removed
- Inspect cylinder head contact surface for flatness, porous or damaged points
- Inspect hardness of cylinder head contact surface, refer to Checking Hardness.

NOTE:
^ If the cylinder head has been subjected to excessive heat, this can result in a change in the microstructure.
^ Machining them will only produces a tight seal of cylinder head/cylinder head gasket/crankcase if certain minimum hardness is achieved.

- Measure height of cylinder head (check dimension H)
- Note reading obtained
- The stock removal at the cylinder head and at the crankcase together should not be more than 0.5 mm.
- If the Cylinder Block (crankcase) has already been machined, the maximum stock removal at the cylinder head contact surface should not be more than 0.3 mm.
- The camshaft housing must not be machined otherwise the basic bores of the camshaft bearings will be altered.
- Test data of cylinder head:
Height of cylinder head (H) without camshaft housing
When new: 126.85-127.15 mm
Wear limit after machining: 126.8 mm
Unevenness of contact surface in longitudinal, transverse direction ≤0.04 mm
Peak-to-valley height: 0.006 mm
Distance (a) for new valves and new valve seat rings
Exhaust valve: 1.300-1.700 mm
Inlet valve: 1.300-1.700 mm
Distance from valve stem end to base of camshaft bearing (T): 23.700-24.200 mm
Hardness of cylinder head contact surface in area of sealing bead of cylinder head gasket: >70
- Once again measure height of cylinder head (check dimension H)
- Measure stock removal.
- After rework of valve seats measure according to the stock removal at the cylinder head
- Measure distance from valve stem end to the base of the camshaft bearing
- Check dimension (T), as follows:
Insert diameter 5 mm round bar into the base of the camshaft bearing for this purpose and measure dimension "T".
or:





- Check dimension (a) see illustration above
Measuring amount by which valve stands back

NOTE:
^ If the measurement obtained is less than dimension "T" or "a", it is no longer possible to achieve correct valve clearance compensation; replace valve seat ring or cylinder head as appropriate
^ Replace valve seat ring. Service and Repair