From the look of it, that valve hit the piston and broke it off. It wedged onto the side of the cylinder and got caught between the piston and head and the piston lost that battle.
So the question is - how did the piston come in contact with the valve? Did you happen to find any extraneous parts? I'm guessing that something found its way into the intake tract, ended up lodging that valve open where it contacted the piston where it bent and/or broke.
Did you happen to check the cam timing before you took the head off? The timing belt could have slipped but that usually leads to every valve getting bent not just one.
--Rob Leone
Schumacher Taxi Service We won the IOE at Southern Discomfort.
We got screwed at The Real Hoopties of New Jersey and we took cars down with us.
We got the curse at Capitol Offense but they wouldn't let us destroy the car.