Hello,
First have the pistons checked. Clean the carbon out of the top ring groove. With a new top ring in place you should not have more than .004" space between the top or bottom of the ring and the groove. The top ring groove on these pistons will wear wider causing the piston ring to move up and down in the ring groove, eventually twisting and breaking.
The skinny top ring and its groove are usually worn the most.
Clean the carbon at the top of the cylinders. If you have enough ridge to catch your finger nail, it is usually worn beyound specs. Cylinders do no wear exactly the same. They wear egg-shapped, and tappered. Putting new perfectly round piston rings in a oval worn cylinder is obviously a problem. A good experienced machinest with the correct tools can tell you exactly the situation.
Sleeving is usually the last resort and used after the block is totally used up. The cylinders are bored completely out and new metal sleeves are pressed into the bored cylinders. The new sleeves are then bored out to the original standard size of the engine. It works quite well. Here again you are dependant on the skill of the machinest, the quality of the steel sleeves and the accuracy of the machinest's edquipment.. a lot of variables! During repairs in the future, the machinest has the option of boring the sleeves to an oversize or replacing the sleeve.
Some engines come from the factory with sleeves already in place. (some Mercedes Diesel engines and most commercial diesel engines). Life expectancy of a commercial diesel will be over one million miles. Sleeving is a more common practice. However other parts like pistons are also beefed up to last, for example, the ring grooves in the aluminum pistons are re-enforced with a nickle/steel alloy so the do not wear.
Early Mercedes Aluminum alloy gasoline engines (M189) came from the factory with alluminum blocks and steel sleeves in the cylinders (quite a technical achievementin 1963).
