I have a Toyota Corolla 89 1.6L, can you help me or give me a procedure on how to do a Engine Top Overhaul? What are the things that needs to be replace? All I know is to replace the valve cover gasket and belts, any suggestion will help.
Doing this overhaul on the cylinder head I would leave to the professionals to repair. To check the cylinder head for wear and what repairs need to bring the cylinder head back into operation (with a long service life). Or replacing the cylinder head completely with a new or re manufactured cylinder head may be the better route to take. However, keep in mind that if your cylinder head is repaired and is now sealing much better now than the pistons could cause the pistons to wear out and cause more blow by resulting poor performance.
Oil leak on the spark plugs could only be a few things the valve cover gasket for the spark plug tube is leaking or the tube where it threads into the cylinder head my be leaking, or a crack in the cylinder head adjacent to the spark plug tube allow oil to leak in (I would suspect the former two before a cracked cylinder head) Hope this answers your question, TY