Contents: Cleaning ⬇ Inspection ⬇
1. A complete cleaning of the cylinder head components and valves followed by a detailed inspection will allow you to determine what procedures need to be performed during an engine overhaul.
Note: If the engine has been severely overheated, it is logical to assume that the cylinder head has become warped, so check this carefully.
Cleaning
2. Clean all traces of old gasket and sealant from the cylinder head; for details see Chapter 6 of Section 2A.
3. Clean any carbon deposits from the combustion chambers and bores, then thoroughly wash the cylinder head with kerosene or a suitable solvent.
4. Scrape off most of the carbon deposits from the valves, then use a wire brush to remove any remaining carbon deposits from the valve heads and stems.
Inspection
Note: Perform all inspection procedures before concluding that it is necessary to contact an auto repair shop for regrinding. Make a list of all components that require regrinding.
Cylinder head
5. Carefully inspect the cylinder head for cracks, signs of coolant leakage, and other damage. If cracks are found, replace the head.
6. Using a steel ruler and feeler gauge, check the deformation of the cylinder head seating surface. Since Skoda does not specify any data on the maximum permissible deformation, if any, consult a Skoda dealer, who can determine the possibility of regrinding the head or purchasing a new one.
7. Inspect the valve seats in each combustion chamber. If they are excessively pitted, cracked or burnt, they must be replaced or reground by an engine rebuilder. If there is slight corrosion, it can be removed by lapping the valve head to the seat as described below. If the valve seats must be reground, this should be done only after the valve guides have been inspected and reconditioned.
8. Inspect the valve guides for signs of wear or damage. If you have the necessary measuring tools, measure the diameter of the valve stems (see below) and guide bores, then calculate the clearance and compare the result with the specified value. If you do not have measuring tools, you can roughly estimate guide wear in the following way. Insert the valve into the appropriate guide so that its head is approximately 10 mm above the surface of the cylinder head, and check the movement of the valve from side to side. There should be very little sideways play. Please note that the valve guides are an integral part of the cylinder head and are not sold separately. Therefore, if the clearance between the stem and the valve guide exceeds the specified Specifications limit, or the lateral play seems excessive, it is necessary to widen the guide bushings and install a new set of valves with stems of the appropriate repair size (nominal diameter 8.25 mm). Leave this work to your Skoda dealer.
Valves
9. Inspect each valve head for pitting, burns, cracks, and general wear, and the valve stem for scratches and worn areas. Rotate the valve to inspect for distortion. Replace any damaged or worn valves.
10. If the valve is in satisfactory condition, measure the stem diameter in several places using a micrometer (see illustration). Any significant difference indicates wear on the valve stem. If any of the above damage is detected, the valve should be replaced.
11. If the valves are not damaged, they should be lapped onto their respective seats to ensure a tight seal.
12. Lapping of valves is performed as follows: Place the cylinder head upside down on the workbench.
13. Apply valve grinding paste (of the appropriate grade) onto the surface of the seat, and attach a special suction cup to the valve head. Rotate the valve back and forth by half a turn, grind its head, grinding it to the seat, sometimes lifting the valve. to redistribute the paste. If you place a weak spring under the valve head, this will make the job much easier.
14. If coarse grinding paste is used, work until the contact surfaces of the seat and valve become dull and matte, then wipe off the compound and repeat the process with fine-grained paste. When the seat and valve surfaces acquire an even light gray color, lapping is considered complete. Do not lap the valves longer than necessary, this will lead to an unwanted deepening of the seat into the cylinder head.
15. When all valves have been lapped, carefully wash off all traces of grinding paste using kerosene or a suitable solvent. Even a small amount of grinding paste remaining in the cylinder head can cause rapid wear.
Valve components
16. Inspect the valve springs for signs of damage and discoloration, and measure their free length using a caliper or steel ruler and compare the obtained values with those specified in Specifications (see illustration). If any of the springs are damaged, distorted, or significantly shorter, purchase a new set of inner and outer springs.
The original can be viewed on SKODABOOK
