A member of our EAA chapter has a cylinder from a Franklin 150 engine
(off the engine.) The piston was pushed too far up and the top ring
sprung out so it now overlaps the cylinder sleeve which locks the piston
in place...

The last time I heard of that happening, the guy sawed the cylinder
head off the top of the cylinder with a bandsaw. In the process, he
zinged the piston pretty bad, pretty much ruining everything there.

My advice would be to see if there's a cylinder overhaul shop with the
capacity of unscrewing the head from the barrel. If so, send it to
them and see if they can rescue it. If not, make a lamp or bookend out
of it.

Thanks, Bob K.