Pic. 2.25. Valve seat angles and lapping
8-valve engines
Normal value: inlet valve - 41.45 mm, exhaust valve - 41.35 mm.
Limit value: inlet valve - 41.95 mm, exhaust valve - 41.85 mm.
12 valve engines
Normal value: inlet valve - 43.70 mm, exhaust valve - 43.30 mm.
Limit value: inlet valve - 44.20 mm, exhaust valve - 43.80 mm.
Valve seat ring replacement
1. Before removing the valve seat ring, first burr on the inside of the ring to facilitate removal. Then replace the ring with a new one.
2. Drill a hole for the valve seat in the cylinder head according to the outer diameter of the valve seat ring, taking into account the allowable repair dimensions.
12 valve engines
Inlet valve (primary):
- Boring by 0.30 mm: 27.421-27.441 mm.
- Boring by 0.60 mm: 27.721-27.741 mm.
Inlet valve (secondary):
- Boring 0.30 mm: 32.425-32.445 mm.
- Boring by 0.60 mm: 32.725-32.725 mm.
Exhaust valve:
- Boring 0.30 mm: 35.425-35.445 mm.
- Boring 0.60 mm: 35.725-35.745 mm.
8-valve engines
Inlet valve:
- Boring by 0.30 mm: 36.300-36.325 mm.
- Boring by 0.60 mm: 36.600-36.625 mm.
Exhaust valve:
- Boring by 0.30 mm: 32.300-32.325 mm.
- Boring 0.60 mm: 32.600-32.625 mm.
3. Before installing the valve seat ring, warm up the cylinder head to 250°or cool the ring to avoid deformation of the hole in the cylinder head.
4. Lap in the valve seat. The angles and lapping of the valve seat are shown in fig. 2.25.