2002 Jeep Liberty Knock after overheat

I have a 2002 jeep liberty with the 3.7 liter motor. It has roughly 140k miles on it.
It had overheated which I believe was due to a bad thermostat(I had diagnosed the issue because prior to the overheat the heat on my jeep was warm at best but never hot)
I then let it cool down for roughly a half an hour
The car was driven roughly 3 miles after the overheat until it had overheated once again, Once again I allowed it time to cool.
When I then tried to start my jeep I then heard a loud knocking sound, and it couldn't maintain even a rough idle.

The sound of the knock is coming from the top of the motor and does not sound like a rod had gone out. I do believe that the overheat had caused one or more of the valves to get excessively hot and then bend because one or more of the rockers had gotten stuck. I have not pulled the heads off yet.

What are the possible and most likely problems?


What are the possibilities of the cylinders walls being scored?
What are the possibilities of a cracked piston?
The reason for the last 2 questions is because if its one of these 2 then I know it will be time for a full rebuild which I don't have the equipment for.

Any help would be greatly appreciated.