I just bought a beautiful mess... care to express an opinion?

[Jake Raby]

Broken valve springs are common, so are failed lifters and both can lead to these conditions you have observed. You need to ensure the valve hasn't gotten bent from operation like this. I have a TON of good used 2.5 parts, including heads and etc, if you need them.

[healthservices]

When looking at the top of the piston, a telltale sign that the valves have touched the pistons is a small shiny crescent shape, where the valves touch.

While not a Porsche piston this will give an idea what the mark may look like.