M;
At TDC see if they "wiggle around", that's the test for rings etc. Solvent can leak through good pistons/rings. How much ring ridge?
If the valves are not split/cracked they may be okay (have compression) to run. Look & see if they (tops) are even (parallel) with the top of the block.
Put some oil on the cylinders before you start turning things etc.
JM......
