Technical Won't come unstuck

Pull the head , fill the cylinders with diesel . Drop a shop towel in each cylinder and light them . As the diesel burns it heat up the piston and cylinders causing the rust or whatever is sticking the pistons to bust loose . This may take a couple try’s . Heat , force and persistence. Will get the job done

 

But the 312 in my 57 Fairlane had a mouse nest in one cylinder. The piston came out in pieces