Note. Standard values for all checks are given in the section «Service data and specification» at the end of this chapter.
Deformation of the cylinder head
Note. When performing this check, it is also necessary to check the deformation of the cylinder block.
1. Remove oil and water film from the surface with a scraper (like inclusions), gasket, sealant, soot, etc.
Note. Be careful not to allow water or gasket particles to enter the oil passages.
2. Using a straightedge and a set of flat feeler gauges, measure the flatness of the cylinder head surface in six directions (A-F). If the results obtained exceed the maximum permissible value, it is necessary to replace the cylinder head with a new one.
If the measured values are not correct, replace the cylinder head with the upper part.
Note. The cylinder head is machined together with the upper part, so it is not possible to replace these parts separately. Replace the cylinder head only complete with the upper part.
Valve sizes
Check the dimensions of each valve.
If the dimensions are not correct, replace the valve and check the fit in the valve seat.
Valve guide clearance
Micrometer (A) measure the diameter of the valve stem.
Measure the inside diameter of the valve guide with a bore gauge.
Calculate valve guide clearance:
(Gap in the guide bush) - (Guide bush inner diameter) - (Valve stem diameter)
If the value obtained is not correct, replace the valve and/or cylinder heads with the upper part.
Valve seat seat
After verifying that the dimensions of the valves and guides correspond to the nominal values, check the correct seating of the valve in the seat.
Apply a thin coat of Prussian Blue to the valve bevel. Press the valve face against the seat, but do not rotate the valve. Then remove the valve and inspect the seat and valve face.
If the ink is imprinted around the entire circumference of the valve seat, the valve guide and valve seat are aligned.
A. Fine.
B. Abnormal.
Otherwise, regrind the chamfer and check again. Replace the valve seat with a new one if the correct seating of the valve cannot be achieved.
Spring Sizes and Elasticity Characteristics
Check the generated load at a certain height of the valve spring, using a special stand.
If at least one of the values obtained is not correct, replace the valve spring with a new one.