[djs]

If I understand my 2.0L pistons, those destined for N. America were originally dished to reduce the compression ratio somewhat, I believe in response to emission constraints. European 2.0 motors in some (if not all?) cases used a flat-top piston, enabling a slighly higher compression ratio (8.0:1 vs. 7.6:1). You can still buy these new. Pelican sells them, and they actually cost a bit less than the dished ones, last time I checked.

In your case, if the ring was stuck in the groove due to carbon buildup, you ***could*** possibly reuse it. In a clean ring groove, you should be able to slip the ring in with no effort. If the ring goes in with any kind of tightness or resistance, something is wrong. The ring has to be able to move freely, as it is designed to push outward against the cylinder wall during combustion. That is the principle behind the compression rings. They use the pressure of combustion to seal tightly against the cylinder walls.

If the piston got hot, it could have distorted permanently. Normally, pistons are not perfectly round when cold. They are slighly elliptical. This is partially due to the fact that the piston is heated unevenly and the skirt area dissipates heat differently then the pin area. When the motor reaches operating temperature, the piston is designed to become round.