Valvetrain Overview

Valvetrain Overview

• The cylinder head and the cylinder head cover must be replaced together.

• Do not start the engine for approximately 30 minutes after installing the camshafts. The hydraulic equalization elements must seat themselves (otherwise the valves will crash into the pistons).

• After working on the valvetrain and lifters, carefully rotate the crankshaft by hand at least 2 full revolutions before starting to be sure that valves do not strike the pistons.

• Always replace the gaskets and seals.






1 Exhaust Valve

• Do not grind, only hand lapping is permitted.

• Valve dimensions, refer to => [ Valve Dimensions ].

• Checking the valve guides. Refer to => [ Valve Guide, Checking ] Testing and Inspection.

2 Cylinder Head

3 Valve Guide

• Checking, refer to => [ Valve Guide, Checking ] Testing and Inspection.

4 Valve Stem Seal

5 Valve Spring

6 Valve Spring Plate

7 Valve Retainers

8 Roller Rocker Arm with Hydraulic Lash Adjuster

• Do not interchange.

• Lubricate the contact surfaces.

9 Exhaust Camshaft

• Check the radial clearance using Plastigage(R) (roller rocker arms are removed).

• Radial clearance at bearing - 24 mm diameter:

0.024 to 0.066 mm

• Radial clearance at bearing - 32 mm diameter:

0.030 to 0.051 mm

• Run out: maximum:

0.04 mm

• Removing and installing, refer to => [ Camshaft ] Service and Repair.

10 Cylinder Head Cover

• With integrated camshaft bearings.

• Clean the sealing surface, reworking is not permitted.

• Remove any old sealant residue.

11 Bolt

• Always replace.

12 O-ring

• Always replace.

• Coat with engine oil.

13 Plug

14 Intake Camshaft

• Check the radial clearance using Plastigage(R) (roller rocker arms are removed).

• Radial clearance at bearing - 24 mm diameter:

0.024 to 0.066 mm

• Run out: maximum:

0.04 mm

• Removing and installing, refer to => [ Camshaft ] Service and Repair.

15 Cap

• Always replace.

• Removing: With the cylinder head cover installed, pierce through one side of the cap with an awl and pry it out.

• Installing: Without sealant, press in 1 to 2 mm using the thrust piece (3334).

16 Intake valve

• Do not grind, only hand lapping is permitted.

• Checking the valve guides, refer to => [ Valve Guide, Checking ] Testing and Inspection.

Cylinder Head Cover Bolt Tightening Sequence





- Replace the bolts.

- Hand tighten the bolts in several steps in sequence - 1 through 6 -.

- Tighten the bolts in sequence - 1 through 6 - to 8 Nm.

- Tighten the bolts in sequence - 1 through 6 - an additional 90° (1/4) turn.

• Ensure the cylinder head cover is not tilted.

Valve Dimensions





• Intake and exhaust valves must not be refaced by grinding. Only hand lapping is permitted.