Valve springs
A special tool is required to correctly check the valve springs, although the exact lengths are not known "tense" springs. When using the device, it should be assumed that all springs have approximately the same elasticity. If a spring tester is not available:
Compare the used spring with the new spring. To do this, clamp both springs in the same vise and slowly twist them. When both springs are compressed to the same amount, this means that they have approximately the same preload. If the old spring compresses to a shorter dimension than the new one, the spring is tired and should be replaced as a set.
Put the springs in order on a flat surface (glass), so that the closed loop is at the bottom. Place a steel corner near the spring. Measure the gap between the spring and the angle in the upper part, it should not exceed 2.0 cm. Otherwise, the spring is bent.
Move the valve plate at the top back and forth and read the readings on the dial indicator. They must not exceed 1.0 mm for intake valves and 1.3 mm for engine exhaust valves.
Check the general condition of the cylinder head before replacing the guide bush. A cylinder head with small scratches between the valve seats or between the valve seat and the first thread of the spark plug can be used further after grinding if the scratches are not wider than 0.3 mm. At the head after grinding, the distance between the arrows (A) should be 132.6mm (four-cylinder engines).
When replacing the guide bushing, the old bushing must be pressed out using a suitable punch (rod) from the cylinder head. To ensure operation, the cylinder head can be heated. The punch used to remove the bushing must have a loaded pin that matches the size of the inside of the bushing.
New bushings should be well lubricated and pressed into the cold cylinder head from the camshaft side until the collar of the bushing contacts the cylinder head. In this case, the press force should not exceed 1 ton, otherwise the collar can be cut off.
Guide bushings must be ground after pressing. Be aware of the difference in the inner diameters of the bushings for different types of engines. For grinding, you can use an adjustable reamer. The valve guides for the intake and exhaust valves are the same. Valve seats should be ground after replacement of bushings.
Valve seats
All valve seats should be checked for wear or gouges. Minor signs of wear can be corrected with a 45°cutter. If the saddle has become too wide, the saddles should be reground. The angle that must be obtained in this case is indicated in the first figure - for the intake valve, in the second - for the exhaust valve. Attention should be paid to the difference in the diameters of the valve seats, which are indicated in "Specifications" for various engines. The seat sizes are different because the intake and exhaust valves themselves are not the same for different types of engines.
Inlet valve seat dimensions
a Valve seat diameter
b Maximum amount of grinding
c Valve seat width, 2D mm
z Cylinder head edge
30°top corner
45°valve seat angle
Exhaust valve seat dimensions
a Valve seat diameter
b Maximum amount of grinding
c Valve seat width, 2 mm
z Cylinder head edge
30°top corner
45°valve seat angle
To determine if grinding is needed, the following measurements should be made:
Insert the valve into the guide sleeve and press firmly against the valve seat.
measure distance (A) between the valve tops and the top edge of the cylinder head.
Calculate the maximum permissible grinding value from the measured value and the permissible minimum value. For intake valves, this value is 33.8 mm and 34.1 mm. The minimum distance for the exhaust valve is 33.0 mm.
If the minimum distance differs from the measured value, the maximum allowable grinding value must be taken. which is indicated in the figures above as (V). In doing so, the following instruction must be observed:
The valve seats must be ground when installing new guide bushings. In doing so, proceed as follows:
Mill a 45°angle and then lightly machine the upper edge of the saddle with a 30°cutter to bring the saddle width to that shown in the table. Milling should be completed when the saddle width is within the specified range.
To avoid too deep a seat in the cylinder head, the above measurement must be made.
Grinded valve seats must be ground in. To do this, the surfaces of the valve seats must be lubricated with some grinding paste and the corresponding valve must be installed in the corresponding seat. Attach the nozzle of a vacuum cleaner to the valve and move the valve back and forth.
After lapping, all parts must be thoroughly cleaned of dirt and grinding paste, check the valve seat on the valve disc and the chamfer. Both parts should show a continuous matt bevel that clearly indicates the width of the valve seat. The latter should be measured as follows:
Draw a few lines on the valve plate with a pencil. The lines should be applied at a distance of approximately 1 mm around the circumference. Then carefully lower the valve into the guide sleeve and seat, turn the valve 90°. Slightly press on the valve.
Pull the valve out and check for worn lines on the valve seat. If the valve seat width is correct, the cylinder head can be reinstalled. Otherwise, the valve seats must be ground, and in the most severe cases, the cylinder head must be replaced.
Valves
Minor damage to the surface of the valve heads can be repaired by lapping the valve in the cylinder head seat as described above.
Measure the valves and replace all valves with the correct dimensions. Attention should be paid to the difference in sizes for different types of engines. The values are in "Specifications".
a Valve disc diameter
b Valve stem diameter
c Valve length.
If wear is found on the edges of the valve stem, it can be abraded with a grinder, but material must not be removed more than 0.5 mm.
Inlet valves can be ground, provided that the value (V) will be at least 0.5 mm. Grinding of exhaust valves is not allowed as they are made of a special material. Exhaust valves can only be lapped with paste or replaced.
a maximum: 3.5 mm
b minimum: 0.5 mm
α — 45°
Attention: Old valves are convenient to use as probes. Those that are filled with sodium should not be used for these purposes.
Cylinder head
Thoroughly clean the sealing surfaces of the cylinder head and check the surface of the cylinder head for warping. To do this, you need to attach a ruler to the head and use a flat feeler gauge to measure the gap in the longitudinal, transverse and diagonal directions in relation to the surface of the head. If a flat feeler gauge more than 0.1 mm thick can be inserted, the cylinder head can be ground. If there is more clearance anywhere, the cylinder head will need to be replaced. By making the above measurement of the cylinder head, it can be determined whether it is large enough to be ground.
Camshaft
The shafts of all engines with 2 valves per cylinder look the same, but the cams are located at different angles so that the valve timing is correct, i.e. to achieve timely opening and closing of the valves. Therefore, it is recommended that when buying a new shaft, take the old one with you. When ordering a shaft, specify the vehicle model number and engine number. Before reinstalling the camshaft, it should be carefully checked. First, put the camshaft between the prisms or clamp it in the centers of the lathe, as shown in the figure, and attach the dial gauge to the middle bearing journal. Slowly turning the camshaft. read meter readings. If the reading exceeds 0.01 mm, then the camshaft is bent and needs to be replaced.
Check bearing journals for visible damage. If there are grooves or other irregularities, the shaft must be replaced. To measure the axial play of the distribution room, it must be placed in the cylinder head (without pushers) and secure with front and rear bearing caps. Place the cylinder head on a level surface. Attach the dial indicator to the end surface, as shown in the figure, and move the shaft in one direction and in the other. The play should not exceed 0.15 mm. Otherwise, the bearing surface of the bearing caps is worn.
Cylinder head assembly
Assembly of a head of cylinders is made in an order, the return to dismantling.
Lubricate the valve stems well with engine oil and install in the appropriate bushings.
Using a special tool, place the lower plates of the valve springs opposite the valve guides.
Install valve stem seals. There is a special device for this (10-204).
plastic sleeve (1) slide the tools onto the protruding bushing.
Stuffing box (2) grease well and put on a plastic sleeve.
fixture (3) place on the stuffing box and carefully press the stuffing box onto the guide bushing. It should be borne in mind that if the oil seal is installed without this tool or the like, the oil seal may be damaged, resulting in increased oil consumption.
If the valves have been lapped, they must be installed in the appropriate seats, since the lapping of each valve is individual.
Install the appropriate inner and outer valve springs on the cylinder head (if the springs are reinstalled).
Hit the top of the valve stem with a plastic mallet. In this case, incorrectly sitting crackers will pop out. As a precaution, you need to put a rag under the ends of the springs so that the parts do not pop out.
Install the pushers according to the previously made marks in the holes (well lubricated with oil), if the old pushers are installed.
Lubricate the camshaft bearing journals well with oil.
Raise the camshaft in the bearings and rotate several times. Finally, turn the camshaft so that the valve lobes of the first cylinder point upwards.
Install bearing caps #2 and #3 and lightly tighten the nuts. Since the lids are of a special shape, you should check if they fit correctly. The figure shows the correct installation of the bearing caps.
Tighten the nuts of the installed bearing caps alternately and crosswise by several turns until a tightening torque of 20 Nm is reached. Check. so that the surfaces of the covers are in contact with the surface of the cylinder head.
Install caps #1 and #3. Screw on the nuts and tighten them alternately crosswise to a torque of 20 Nm.
Take the camshaft oil seal in your hand and determine which side the spring is on. Turn the side where the spring is inward and lightly grease the lip of the stuffing box (as well as the surface of the shaft). To install a new oil seal, use a piece of pipe of a suitable diameter. The pipe must be in full contact with the outer circumference of the stuffing box. Install the gland and hammer it so that it is flush with the outer surface of the head. You can install the oil seal in the same way as described for the crankshaft front oil seal.
Slide the camshaft drive gear onto the shaft (do not forget the key and check the correctness of its installation) and tighten the bolt with washer. Holding the gear in a suitable way (e.g. using an old toothed belt), tighten the bolt to a tightening torque of 8Nm.
Install the rest of the parts in the cylinder head, with the exception of those that are installed when installing the head.
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