Using the edge of a straightedge and a feeler plate, check for deformation on the surface of the cylinder head in contact with the cylinder block.
If the deformation is greater than the maximum allowable value (0.05 mm), the surface must be processed on the machine, not exceeding the required limit value.
Check the valve seats in each of the combustion chambers. If they are scorched, cracked, or pitted, the valve seats must be replaced.
Check the clearance between the stem and valve guide by measuring the horizontal stem play with a gauge with an indicator. To determine the gap between the valve stem and valve guide, shake the stem and take measurements at the extreme points using an indicator. The valve should be raised about 1.5 mm. In order to get the true value of the gap, the result must be divided by two. If the clearance is greater than the allowable value, the guide bushings must be replaced.
Valves
Carefully inspect each valve for signs of wear, cracks, gouges and burnt areas. Rotate the valve and see if it is bent. If any of the above is found, the valve must be repaired by a specialist workshop.
Check for valve wear.
Check valve wear at specified points
A - inlet valve;
B - exhaust valve;
1 - the end of the valve;
2 - cracker groove;
3 - rod (least worn area);
4 - rod (most worn area);
5 - valve surface;
6 - edge.
Measure the protrusion of each valve from the seat (for the intake valve - 1.191 mm, for the exhaust - 1.98 mm). If it is smaller or missing, the valve must be replaced.
Valve parts
Check each valve spring for wear (at the ends) and pitting corrosion. Measure the free length and compare with the technical data. Springs that are shorter than the permitted length must not be used again. The tension of all springs must be checked with a special device before deciding on their suitability (these measurements are carried out in a specialized workshop).
Place each spring on a flat surface and check for squareness.
If the springs are deformed, replace them as they can cause accelerated wear of the guide bushings.
Check cymbals and holders for wear and cracks. All questionable parts must be replaced with new ones.
Rocker parts
Check rocker arms that contact tappet ends and valve stems for pitting, wear, deposits, and scratches. Also check the hinges. Check for cracks on rocker arms, bolts and nuts.
All damaged or badly worn parts should be replaced with new ones.
If the inspection showed that the valve parts are in poor condition and worn beyond the allowable (which is usually the case in engines undergoing overhaul) valves and seats must be replaced or lapped.