Dismantling and assembly of the cylinder head of the VAZ-2112 engine

We have covered the removal of the cylinder head in the article. In this article we will cover the dismantling and reassembly of the cylinder head.

Important! When dismantling the cylinder head, the parts must be marked and laid out in order.

Dismantling the cylinder head

1. Using an 8 mm socket, we unscrew the 20 bolts securing the camshaft bearing housing.

2. We remove the camshaft bearing housing.
3. We withdraw the spark plug guide tubes from the housing.

Near the first journal, a band is machined on the inlet camshaft.

4. We withdraw the camshafts with their oil seals.

5. We extract the two plugs from the camshaft ends.

6. Using a magnet, we extract the hydraulic tappets from their bores and lay them out in order.

7. Using a 13 mm spanner, we unscrew the two nuts securing the cooling system pipe.

8. We remove the pipe.

9. Using a 21 mm spanner, we unscrew the coolant temperature sensor.

Dismantling the valve mechanism

We place a wooden block under the valve heads. We fit the valve spring compressor. The pad of the compressor is placed on the valve spring retainer, and the hook lever is hooked behind the head of a bolt screwed into the cylinder head hole intended for securing the bearing housing.

10. We press on the lever and compress the valve spring. With tweezers we extract the two valve collets.

11. We extract the spring retainer.

12. We remove the spring.

13. To extract the oil deflector caps we use special pliers.

14. We remove the valve stem seals from the guides.

15. We remove the valves from the cylinder head guides and lay them out in order.

Checking the cylinder head

1. Check the flatness of the surface mating with the cylinder block. To do this, place a straightedge on edge on the cylinder head surface, first along the middle, then along the diagonals, and measure the gap between the cylinder head surface and the straightedge with a feeler gauge. If the gap exceeds 0.1 mm, the mating surface may be ground.

2. Similarly, check the flatness of the cylinder head mating surfaces under the inlet manifold. The out-of-flatness of these surfaces must not exceed 0.1 mm.

Checking the cylinder head for leaks

To check the cylinder head for leaks, blank off the hole in the head under the thermostat seat. This can be done, for example, by fitting a blank gasket made of stout cardboard under the seat and tightening its mounting nuts. Refit the coolant temperature gauge sensor if it has been unscrewed.

Checking and grinding in the valves

1. We clean carbon deposits from the valve.
2. We visually check the condition of the valve. We replace the valve if there are deep scores on the working chamfer 1, cracks, deformation of the stem 3, warping of the valve head 2, or signs of burning.

3. Shallow scores and scratches on the valve working chamfer can be removed by grinding in the valves. To do this, we apply a continuous thin layer of grinding paste to the valve chamfer.

4. We slip a pre-selected spring onto the valve stem and insert the valve into the guide from the combustion chamber side. On the valve stem itself we apply graphite grease so that the grinding paste does not get onto the valve guide surface.

5. We slip onto the valve stem the valve grinding tool or a reversible drill with a hose adaptor for connection to the valve. Switching the drill on at the minimum speed (in reverse mode) or turning the tool (in the case of manual grinding) alternately half a turn in each direction, we grind in the valve, periodically pressing it against the seat and then easing off the pressure.
6. An external sign of satisfactory grinding-in is the uniform matt-grey colour of the valve working chamfer. A uniform grey band must also appear on the valve seat.

7. After grinding in, the valve and valve seat must be thoroughly wiped free of grinding paste.
8. Check the valve for leaks by fitting it with its springs and collets into the head. Then lay the head with the combustion chambers upwards, blank off the spark plug hole and pour paraffin into the combustion chamber. If the paraffin does not seep into the cylinder head port within 3 min, the valve is leak-tight.

Checking the hydraulic tappets

Inspect the valve hydraulic tappets. If there are scratches or other defects, replace the hydraulic tappets. Measure the outside diameters of the tappets and replace any worn tappets.

The working surfaces 2 must be free from scoring, dents, scratches, signs of stepped or uneven wear, and metal smearing. Hydraulic tappets with such defects must be replaced. Concentric running-in marks from the camshaft cams are permissible on surfaces 2.

Checking the clearances between the guides and the valves

The clearance is calculated as the difference between the diameter of the hole in the guide and the diameter of the valve stem.

Clearances between the valve and the guide, mm:

• nominal for inlet and exhaust valves – 0.018-0.047;
• maximum permissible for inlet and exhaust valves – 0.3.

If the clearance has not reached the maximum permissible value, an attempt can be made to eliminate it by replacing the valve. If this cannot be done or the clearance exceeds the maximum permissible value, replace the guide.

To do this, press the defective guide out from the combustion chamber side with a drift, having first measured the height by which the upper part of the guide protrudes above the cylinder head surface. Cool the new guide, for example with carbon dioxide, lubricate it with oil, insert it into a special drift and press it in from the camshaft side so that the height by which the upper part of the guide protrudes corresponds to the measured value. Ream the hole in the guide with a reamer to 7.0 – 7.015 mm for inlet and exhaust valves.

Reassembling the cylinder head

We reassemble the head in the reverse order, bearing in mind the following:

1. To press in the oil deflector caps we use a special drift.

2. We lubricate the new oil deflector cap and press it onto the valve guide.
3. We fit the cylinder head to the engine – (read the article on fitting the cylinder head).

4. We fit the valve hydraulic tappets.

5. We lubricate the camshaft bearings and the hydraulic tappets.

6. We fit the camshafts into the head bearings so that the No. 1 cylinder cams point away from the valve tappets.

7. We lubricate the camshaft journals with engine oil.

8. We lubricate the camshaft cams.

9. We apply sealant to the surface of the bearing housing.

10. We fit the bearing housing and evenly tighten the mounting bolts in a crosswise sequence.
11. Having lubricated the guide tube sealing rings with engine oil, we fit the tubes.
12. On the other side of the cylinder head we press in the plugs.