Bold reference numbers in this section identify parts not shown in the figures alongside the text, but which can be found in the exploded view diagram.

On disassembly of the components mounted on the cylinder head it is essential that they are laid out or marked in such a way that they can be refitted in exactly the same position they occupied before being removed.

Using tool 88713.2676, unscrew the nuts (19) on the cylinder head studs.

Screw service tool 88713.2837 to the threaded end of the opening rocker shaft (4).

Slide the valve closing shim (8) along the intake valve stem (17) in such a way as to make it possible to remove the two half rings (7) securing the valve.

Attach the end of the spring (9) of the closing rocker arm (18) to the tool 88713.2783.

Remove the closing rocker arm shaft (4) using service tool 88713.2837.

Remove the rocker arm (18), the spring (9) and service tool 88713.2783.

The cylinder barrel mating surface must be perfectly flat. If this is not the case, spread diamond dressing compound (6 to 12 micron thickness) on a reference surface and slide the cylinder head on the surface as shown in the figure until a flat finish is obtained.

Check that the stem and the valve seat contact surface are in good condition. There must be no pitting, cracks, deformations or signs of wear.

Perform the following checks: measure the diameter of the valve stem (D) at various heights along the portion that runs in the valve guide.

Check that valve head band (at 45° to valve head top face) is concentric to the valve stem as follows: place the valve on a V block, set a dial gauge at right angles to the head and rotate the valve.

Service limit: 0.03 mm.

If a valve seat is only slightly damaged, it may be lapped using the special 45° lapping tools, with subsequent grinding of the valve into its seats.

If the valve seats are excessively damaged, fit oversize seats. Replacement seats are available with 0.03 and 0.06 mm oversized outside diameters.

Check the diameter of cylinder head bores and choose the oversized valve seat that will give an interference fit of 0.11 to 0.16 mm. Replacement valve seats are supplied in outside diameter oversizes of 0.03 and 0.06 mm.

Heat the cylinder head gradually and evenly up to 200 °C and chill the new valve seats in dry ice.

Use Prussian blue or a mixture of minium and oil to check that the contact surface (W) between valve and seat is 1.0 to 1.5 mm.

Carefully examine the internal surface of the valve guide: for cracking or distortion. If the guide is excessively out-of-round, use a reaming tool to make the mating faces more uniform.

When you change the valve guide, you must also change the valve. The intake valve guides are made from cast iron, whereas the exhaust valve guides are bronze.

To renew the valve guides (11) and (13), proceed as follows.

Heat up the cylinder head gradually and evenly up to 200 °C.

Select the most suitable replacement valve guide to obtain an interference fit in the cylinder head bore of 0.022-0.051 mm; replacement valve guides are supplied in O.D. oversizes of 0.03, 0.06 and 0.09 complete with lock rings.

Lubricate the seat and install the valve guide so that the stop ring is located against the head, using the drift previously used to remove the old guide.

The assembly clearance must be 0.03 to 0.06 mm.

In the event of excessive clearance, fit 0.02 mm oversize shafts (available from Parts Service).

Carefully examine the springs (9) of the closing rocker arms (18). There must be no signs of cracking, distortion, or loss of elasticity.

To refit the cylinder head reverse the steps of the removal procedure; pay particular attention to those operations mentioned specifically.

If removed, fit new valve guide seal rings (10), lubricate with engine oil and insert from the spring side with tool part no. 88713.2442.

Fit the closing rocker arm (18) and relative spring (9) on service tool no. 88713.2783.

Insstall the service tool-rocker arm-spring assembly in the cylinder head and insert the shaft (4) with a new seal ring (5), suitably lubricated.

Detach the spring (9) and remove the tool 88713.2783.

Reposition the screwdriver, and compress the spring as much as possible while holding the valve, the shim and the half rings in the “valve closed” position. Release the closing rocker (18) with a rapid motion, so that the half rings seat in the shim.

With the valve in rest position and while pushing on the rocker arm to oppose the force of the return spring, check that the clearance between the rocker and the closing shim is within the specified tolerance limits (Sect. N 4.1, Checking the closing clearance (Sc) of the intake/exhaust valves).

If not, adjust the valve clearance (Sect. N 4.1, Checking and adjusting valve clearances).

Once the specified clearance has been obtained, remove the camshaft (C), lubricate it with graphite oil and reinstall it in the cylinder head.

Insert the rocker arm shaft (4) with the threaded hole on the external side of the cylinder head: the seal (5) should be renewed on installation; lubricate it before fitting.

Refit the camshaft end cap (Sect. N 4.3, Refitting the camshaft end caps).

Refit the camshaft timing pulleys (Sect. N 4.2, Refitting the timing belt driveshaft pulleys).

With the valve in rest position, check that clearance between the rocker arm (3) and the shim (6) is within the specified tolerance limits (Sect. N 4.1, Checking the opening clearance (Sa) of the intake/exhaust valves).

If not, adjust the valve clearance (Sect. N 4.1, Checking and adjusting valve clearances.

In order to prevent oil leaks developing between the cylinder barrel and the crankcase, every time the cylinder head is removed, it is essential to remove also the cylinder barrel/piston in order to be able to clean the crankcase and cylinder barrel, to renew, if necessary, damaged gaskets and O-rings and to apply new liquid gasket (Sect. N 5, Refitting the cylinder/piston assembly).

Before refitting the cylinder head assemblies, fit new head gaskets (C) and check that the locating dowels (A) and bushes (B) are installed (Sect. N 5, Cylinder/piston assemblies).

Fit the special washers (12) over the stud bolts with the square edged face towards the cylinder head and the flat face towards the inside.

Using tool no. 88713.2676 in conjunction with a torque wrench, gradually tighten the cylinder head nuts to the specified torque in a crosswise sequence (Sect. C 3, Engine torque settings).