Valve stuck again...

Couple of questions.... Has it always been the same valve? Is the valve bent? mark it before you remove it to see which way it was bent, what was the installed height versus full open?
One more thing. When you get the engine back together and running, hook up a timing light. Starting at #1 than going to what # your working one. The deal is that the timing light will Freeze a part in motion when you shine it on a part your looking at and you will be able to see if any of the parts are bending, rotating like they should, flexing or doing something strange. Also, it's a great way to find a bent fan blade in motion put a number in chalk on each one.
Any way hope this helps. Good Luck!Bill