Try this trick, take all the plugs out, put some marvel down each plug hole with some seafoam. Let it sit overnight, next day turn it over BY HAND with the plugs still out, put some more marvel and seafoam down there, next day turn it over again by hand. Then the day after that just dump some seafoam down each sparkplug hole, put the plugs back in and start er up. It'll smoke like hell and probably foul the first set of plugs, but should pop the rings loose if they are indeed stuck.