General information
1 The rocker arm assembly is secured to the top of the cylinder head by the cylinder head bolts. Although in theory it is possible to undo the head bolts and remove the rocker arm assembly without removing the head, in practice, this is not recommended. Once the bolts have been removed, the head gasket will be disturbed, and the gasket will almost certainly leak or blow after refitting. For this reason, removal of the rocker arm assembly cannot be done without removing the cylinder head and renewing the head gasket.

2 The camshaft is slid out of the right-hand end of the cylinder head, and it therefore cannot be removed without first removing the cylinder head, due to a lack of clearance.

Removal
Rocker arm assembly
3 Remove the cylinder head as described in Section 7.

4 To dismantle the rocker arm assembly, carefully prise off the circlip from the end of the rocker shaft; retain the rocker pedestal, to prevent it being sprung off the end of the shaft. Slide the various components off the end of the shaft, keeping all components in their correct fitted order (see illustrations).

6.4a Prise off the circlip (arrowed) from the end of the rocker shaft . . .

6.4b . . . and slide the components off the shaft

Make a note of each component’s correct fitted position and orientation as it is removed, to ensure it is fitted correctly on reassembly.

5 To separate the remaining pedestal and shaft, first unscrew the rocker cover retaining stud from the top of the pedestal; this can be achieved using a stud extractor, or two nuts locked together. With the stud removed, unscrew the grub screw from the top of the pedestal, and withdraw the rocker shaft.

Camshaft
6 Remove the cylinder head as described in Section 7.

7 Undo the retaining bolt, and remove the camshaft retaining thrust plate from the cylinder head (see illustration).

6.7 Camshaft retaining thrust plate

8 Withdraw the camshaft taking care not to scratch the bearing journals with the edges of the cam lobes (see illustration).

6.8 Removing the camshaft

Inspection
Rocker arm assembly
9 Examine the rocker arm bearing surfaces which contact the camshaft lobes for wear ridges and scoring. Renew any rocker arms on which these conditions are apparent. If a rocker arm bearing surface is badly scored, also examine the corresponding lobe on the camshaft for wear, as it is likely that both will be worn. Renew worn components as necessary. The rocker arm assembly can be dismantled as described in paragraphs 4 and 5.

10 Inspect the ends of the (valve clearance) adjusting screws for signs of wear or damage, and renew as required.

11 If the rocker arm assembly has been dismantled, examine the rocker arm and shaft bearing surfaces for wear ridges and scoring.

If there are obvious signs of wear, the relevant rocker arm(s) and/or the shaft must be renewed.

Camshaft
12 Examine the camshaft bearing surfaces and cam lobes for signs of wear ridges and scoring. Renew the camshaft if any of these conditions are apparent. Examine the condition of the bearing surfaces, both on the camshaft journals and in the cylinder head. If the head bearing surfaces are worn excessively, the cylinder head will need to be renewed. If the necessary measuring equipment is available, camshaft bearing journal wear can be checked by direct measurement, noting that No 1 journal is at the transmission end of the head.

13 Examine the thrust plate for signs of wear or scoring, and renew as necessary.

Refitting
Camshaft
14 Ensure that the cylinder head and camshaft bearing surfaces are clean, then liberally oil the camshaft bearings and lobes.

Slide the camshaft back into position in the cylinder head.

15 Locate the thrust plate in position, refit the plate retaining bolt, tightening it to the specified torque setting.

Rocker arm assembly
16 If the rocker arm assembly was dismantled, refit the rocker shaft to the pedestal, aligning its locating hole with the pedestal threaded hole. Refit the grub screw, and tighten it securely. With the grub screw in position, refit the rocker cover mounting stud to the pedestal, and tighten it securely. Apply a smear of clean engine oil to the shaft, then slide on all removed components, ensuring each is correctly fitted in its original position.

Once all components are in position on the shaft, compress the remaining pedestal and refit the circlip. Ensure that the circlip is correctly located in its groove on the shaft.

17 Refit the cylinder head and rocker arm assembly as described in Section 7.