2. To remove the valves, it is necessary to compress the springs so that you can pull the crackers out of the groove at the top of the valve stem.
3. Position the spring compressor so that the fork at the end of the lever rests on the valve spring plate and the clamp screw rests against the surface of the valve head.
4. Tighten the clamp to compress the springs and relieve the pressure of the spring plate on the crackers. If the disc gets stuck, hold the valve head and lightly tap the clamp with a hammer.
5. Remove 2 crackers, release the spring and remove the compressor. Remove the plate and spring and take out the valve.
b. As you remove the valves, arrange them in order so that they do not get mixed up during installation. You can take a piece of cardboard, make 8 holes in it and insert valves into them.
7. Remembering that the cylinder head is made of light alloy, clean it from carbon deposits with a blunt scraper or a rotary wire brush. The valve stems and guide bushings also need to be cleaned. Wash the combustion chambers and all openings with kerosene and clean the outer surface of the head with a blunt scraper.
8. If the engine is in the car, clean the pistons and the top of the cylinders. If the pistons are still in the cylinder block, be careful not to let any of the carbon deposits you remove fall into the cylinders, as they may scratch the cylinder walls and cause damage to the pistons and piston rings. To prevent this from happening, you should first turn the crankshaft so that the 2 pistons are in the upper position. Plug the other 2 cylinders with rags or cover them with paper. The water jacket passages should also be covered to prevent dirt from entering the cooling system and damaging the water pump.
9. Apply a small amount of grease to the space between the pistons and the cylinder walls and use a blunt scraper to scrape off any carbon deposits from the piston crowns, being careful not to scratch the aluminum. Clean off any carbon deposits from the adjacent edge of the cylinders as well. Remove contaminated grease, being careful not to force it into the cylinders. To prevent carbon deposits from accumulating, the piston bottoms can be treated with a metal polishing paste, but be sure to remove all traces of the paste afterwards. Remove the rags from the remaining two cylinders and turn the crankshaft so that the pistons in them are in the upper position. Plug the cleaned cylinders with rags and repeat the above procedure.
10. Inspect the valve heads for pitting and burning (especially the exhaust valve heads). At the same time, inspect the valve seats. In case of minor ulceration of valves and seats, defects can be removed during valve grinding.
11. If the valve seats are severely pitted, they will have to be re-cut and new valves installed (produced by a specialist). In practice, it is extremely unlikely that saddles will be very worn. Replacements usually require valves. New valves must be lapped into their seats.
12. Lapping of valves is performed as follows. Apply a small amount of coarse carborundum paste to the valve seat and place the lapping tool on the valve. Using semi-rotary movements, grind the valve head to the seat, occasionally lifting the valve and redistributing the lapping paste. Once dull matte stripes appear on the valve seat and head, wipe off the paste and repeat the entire process with fine carborundum paste. Lapping will be made much easier if you install a weak spring under the valve head. Once smooth matte stripes of light gray color appear on the valve seat and head, grinding can be considered complete. Carefully wipe off all traces of paste from the valves and seats, making sure that it does not get into the holes or valve guides. Wipe the valves and seats with a rag soaked in kerosene, then with a clean rag and blow out the valves, guide bushings and all openings with compressed air.
13. Inspect the valve springs - damaged springs must be replaced. Check the free length of the springs (relatively new springs). Springs that are not long enough must be replaced. Springs are subject to fatigue and it is recommended to replace them even if they appear to be in good condition.
14. Check the cylinder head for deformation, either by placing it on a glass sheet or using a ruler and thickness gauges. If there is even the slightest distortion of the sealing surface of the head, it should be taken to a specialist for processing.
15. On 1.6 and 1.8 engines, at each overhaul of the head, the sealing ring between it and the thermostat housing should be replaced. Replacing the sealing ring is extremely difficult if the head is still in place on the engine (see chapter 2).
16. If it is necessary to replace the pressure regulating valve located in the cylinder head, access to it is provided through the ring plug covering the end of the valve. The old valve should be broken, its remains pulled out and a thread (M10) cut into the valve seat so that it can be removed using a suitable bolt. After this, you can drive the new valve into place together with the plug. Considering the certain complexity of this operation, it is recommended to entrust it to a specialist.
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