Valve sizes for a four-cylinder engine
inlet valve | Exhaust valve | |
a
|
40.0 mm
|
33.0 mm
|
b
|
7.97 mm
|
7.95 mm
|
With
|
91 mm
|
90.8 mm
|
Valve seat dimensions
Valve seat dimensions:
- A) inlet valve
- b) exhaust valve
Order of execution
1. After disassembling the block head, rinse all parts in gasoline, wipe and dry. Clean the combustion chambers and valves from carbon deposits.
2. Check the block head. If there are cracks on the walls of the combustion chamber, traces of burnout, etc., replace the block head.
3. Check with a metal ruler and feeler gauges whether the flatness of the surface of the head adjacent to the block is not disturbed. To do this, put the ruler with an edge on the surface of the head of the block in the middle, along and then across and measure the gap between the surface of the head and the ruler with a feeler gauge. If the gap exceeds 0.1 mm, the head is replaced or ground. The minimum allowable head height is 132.75 mm. If the height of the head is reduced during grinding, the head must be replaced.
4. Check the head for cracks, to do this, bring a hose for supplying compressed air to one of the holes in the cooling jacket. Plug all holes in the head with wooden plugs. Lower the head into a bath of water and apply compressed air at a pressure of 1.5 atm. In places where there are cracks, air bubbles will come out.
5. Check valves. If cracks, warping of the valve head, burnout, deformation of the stem are found on the working chamfer of the valve, the valve must be replaced.
6. Minor scratches and scratches on the working bevel of the valve can be removed by lapping. The valve to the seat should be lapped as follows:
- insert the valve into the block head;
- put a valve grinding tool on the valve stem;
- apply a thin layer of lapping paste to the working chamfer of the valve;
- turn the valve using the device in both directions, periodically pressing it against the seat. An external sign of satisfactory lapping is the uniform matte gray color of the working chamfer and valve.
7. After lapping, thoroughly rinse the seat and valve and wipe thoroughly with a clean cloth to remove any remaining lapping paste.
8. To check the tightness of the valve, install it in the head of the block along with springs and crackers. After that, put the head of the block on its side and pour kerosene into the channel closed by the valve. If kerosene does not seep into the combustion chamber within 3 minutes, the valve is considered tight. Valve dimensions are shown in fig. Valve sizes for a four-cylinder engine.
9. Check the condition of the valve springs. Twisted springs, as well as those with cracks or broken ones, are replaced.
10. Check the condition of the valve seats. Seat faces must be free of wear, pitting, corrosion, etc. Minor damage (small risks, scratches, etc.) can be removed by lapping the valves. More significant defects are eliminated by grinding. When grinding, the dimensions of the saddle shown in fig. Valve seat dimensions.
11. After grinding, grind the valves. Then thoroughly clean and blow out the head of the block with compressed air so that no abrasive particles remain in the channels closed by the valves and in the combustion chambers.
12. It should be noted that after grinding the seat, the valve sits deeper in the seat. Therefore, on engines with hydraulic valve lifters, after grinding, it is necessary to measure the distance a between the end of the valve stem pressed against the seat and the upper plane of the block head. If this size is less than 33.8 mm for intake valves and less than 34.1 mm for exhaust valves, the block head should be replaced, since in this case the normal operation of the valve lifters is disrupted. Thus, the reduction in the working chamfer of the valve seat should not be greater than the difference between the size a before grinding and the minimum allowable size a.
13. Check clearances between guide bushings and valves. To do this, insert the valve into the guide sleeve so that the end of the valve stem is flush with the end of the guide sleeve.
14. Install the indicator foot to the valve head. Moving the valve from stop to stop in a horizontal plane, measure the gap. If inlet valve travel is greater than 1.0mm and exhaust valve travel is greater than 1.3mm, replace bushings and valves. The diameters of the inlet and exhaust valve stems are different, so you need to check the inlet valve bushings by inserting the inlet valve, and the exhaust valves by inserting the exhaust valve.
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