Start out with a good dose of penetrating oil in the cylinders, hopefully to free up the rings. Kano Kroil, made in Nashville, is by far the best penetrant out there.

www.kanolabs.com

There's at least as good a possibility you're dealing with sticky valves, rather than ring problems. Take the valve cover off, and soak the tops of the valve guides with Kroil, then work the valves up and down repeatedly with a pry bar. Worst-case scenario, you'll need to pull the cylinder head and oil pan, and inspect the cylinders and valves.
Jerry

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