Arrangement of cylinder head cover seals and reinforcement plates with a gasket contact surface width of 5.5 mm
A, B – reinforced plate, C – seal
Arrangement of cylinder head cover seals and reinforcement plates with a gasket contact surface width of 8 mm
A, B, D – reinforced plate, C – seal
Identifying Cylinder Head Bolts
A – T55 Torx bolt, B – T55 Torx internal star bolt
Since September 1983 (manufacture date code "DJ") all engines have been equipped with a cylinder head with an increased (from 5.5 mm to 8 mm) width of the cylinder head cover gasket mating surface.
Since April 1984, the cylinder head bolts used are the Torx T55 type with an internal hexagonal head. The tightening order has not changed.
If oil leaks from under the cylinder head cover in a vehicle manufactured before September 1983 with a 5.5 mm wide gasket surface, proceed as follows.
1. Remove the cylinder head cover and straighten the damaged or deformed surface of the head cover support.
2. Install the cylinder head cover together with the new type gasket and six additional seals.
3. Replace the corner plates (Grower type) with four reinforced plates.
If the gasket mating surface in the cylinder head cover cannot be restored to normal condition, then the following steps should be taken.
1. Install the following new type components: cylinder head cover and gasket, and timing belt cover.
2. Replace the corner plates (Grower type) with four reinforced plates and install six additional seals.
If the cylinder head cover gasket needs to be replaced on a vehicle manufactured after September 1983, proceed as follows.
1. Install reinforced plates.
2. Tighten the cylinder head cover mounting bolts to 5–8 Nm.
Torx T55 Cylinder Head Bolt Tightening Torques
| Stage 1 | 35 – 40 Nm |
| Stage 2 | 70 – 75 Nm |
| Stage 3 (after 5 minutes) | tighten to 90 |
Caution! The T55 Torx socket cylinder head bolts are single-use bolts. Always use new Torx socket bolts to secure the cylinder head. Torx socket bolts must not be tightened on a warm engine. VALVES
Dimensions of valves of ONS engines 1.6 dm³ LSD and 1.8 dm³ REB
| Engine | 1.6 dm³ LSD | 1.8 dm³ REB |
| Inlet valve: | ||
| – length (mm) | 112,55 | 111,75 – 112,75 |
| – plate diameter (mm) | 41,80 – 42,20 | 41,80 – 42,20 |
| Exhaust valve: | ||
| – length (mm) | 112,55 | 111,15 – 112,15 |
| – plate diameter (mm) | 34,00 – 34,40 | 34,00 – 34,40 |
Valve stroke
| Engine 1.6 dm³ LSD | 9.5 mm |
| Engine 1.8 dm³ REB | 10.1 mm |