Execution sequence
1. Remove the cylinder head («Cylinder head - removal and installation»).
2. We clean the block head from dirt and carbon deposits, wash it from oil deposits, remove carbon deposits from the walls of the combustion chambers with a metal brush.
3. Carefully inspect the cylinder head. They should not have cracks. On the working surfaces of the camshaft bearings and the walls of the tappet bores, there should be no scoring and traces of metal enveloping. The guides and valve seats must fit snugly in the body of the head, with no traces of their mixing during timing operation. Valves and their seats must not have cracks or burn marks.
4. Check the flatness of the head.
Tip: This requires a special template, but if it is not there, then you can check the lower mating plane of the head with a sufficient degree of accuracy using a wide locksmith's ruler.
Sample (ruler) we apply with an edge to the mating plane diagonally of the head.
We make sure that there is no gap between the edge of the template (rulers) and head plane. The gap can be observed both in the middle part of the plane and along its edges. We measure the gap along both diagonals with a set of flat probes.
The maximum allowable gap is 0.1 mm.
Recommendation. If the gap is greater than the allowable, the head must be replaced.
5. Check the tightness of the block head. To do this, close the window for supplying coolant to the thermostat with a plug on the end surface of the head.
We turn the head over and fill its internal cavities for coolant with kerosene.
7. We make sure that there is no leakage of kerosene from the head of the block.
If the level of kerosene in any chamber drops, one or both valves are leaking.
Recommendation. If a leak is found, the block head must be repaired or replaced.
Lapping
1. Remove the valve stem seal («Oil seals - replacement»).
2. Remove the valve from the guide sleeve.
3. Apply lapping paste to the working edge of the valve.
4. We install the valve in the head of the block and fix the device for lapping the valves on its stem.
5. Pressing the valve against the seat, turn it from side to side. After 10-15 strokes turn the valve 90°and continue lapping.
6. Lapping is carried out until a uniform annular mark is formed on the valve disc...
...and his saddle.
7. Remove the remnants of lapping paste from the valve and its seat.
8. Similarly, we grind the remaining valves.
9. After grinding, we re-check the tightness of the valves (see above).
10. If the kerosene does not go away, install new valve stem seals and valve in the reverse order of removal.