Remove the spark plugs, raise the right side of the car as much as you safely can to help level the pistons. Inject/squirt enough Marvel Mystery Oil into each cylinder to barely cover the tops of the pistons and let it soak for days if possible. Put the spark plugs back in loosely to keep the plug hole sealed. Very gently and slowly rock the engine a little BY HAND ONLY while it soaks. After a few days remove the spark plugs and rotate the engine several times by hand and then crank it over with the starter with the plugs removed. This will be messy be prepared with rags to capture MMO spraying out of the cylinders. I’d disconnect the coil in the beginning to prevent spark near an open plug hole in case it sprays oiut any gasoline causing a fire.

Install the plugs and start the engine expecting smoke that will need driving’to clear. Warm it up and drive it hard up hills if possible and let it coast downhill, this causes the rings to move back and forth in the piston grooves.

It would be interesting if you could do a before and after compression test but remember this soak is to clear up oil control rings, compression rings can be very stubborn to free if they are stuck.

Remember to NOT crank the engine with the starter with the spark plugs installed with any liquid in the cylinders. This will bend things in the engine.

Good luck!!!