Scrap all traces of gasket material from the cylinder block. Be careful not to scratch the surface of the block.
Remove the main bearing caps and pull out the bearing shells. Tag earbuds (from which cylinder, whether they were in the cover or cylinder block) and put them aside.
Pull out all threaded plugs of the oil passages. Usually they do not get out, and they have to be drilled. For now, plug the holes with rags, and when assembling, put new plugs.
The cylinder block is usually steam cleaned at the workshop, but with the right precautions, this can be done at home.
After steam cleaning, clean all holes and oil passages again using special brushes. Rinse the channels with warm water until the water comes out clear. Dry the block thoroughly and wipe all machined surfaces with an anti-corrosion oil.
If the block is not too dirty, you can clean it with hot soapy water and a stiff brush. Regardless of the cleaning method, thoroughly clean all oil holes and passages, dry the block completely, and apply oil to all machined surfaces.
Run a suitable tap through all threaded holes to remove corrosion, deposits and sealant residue. If possible, after this operation, blow out the holes with compressed air to remove the formed small particles.
Install the main bearing caps and finger-tighten the bolts.
Apply sealant to the new plugs and install them in the holes. Insert the plugs into place with a bushing and a hammer - drive slowly and stop when the plug is flush with the block. Make sure the plugs are not skewed and fit correctly.
Place the plug in place with a bushing that is slightly smaller in diameter than the plug and hammer.
Apply a non-hardening sealant to the oil passage screw plugs and screw them into the holes in the block. Make sure they are securely tightened.
If the engine will not be assembled immediately, cover it with plastic wrap to keep it clean.