Yeah i know, could try that!Is the head off right now? Could you take some Playdough and put it in the valve cutouts on the piston (then light coat of oil so valve doesn't stick) to see which of the valves happens to be hitting? Like which valve has an abnormal piston-valve clearance? Cause unless you left something screwed into the spark plug holes it has to be a valve.
Maybe one of the shims is slightly off center under the bucket and that is causing one valve to stick out more? Sorry I'm all over the place it's a very odd situation you describe.
I think its really odd as well, cant wrap my head around it and seriousky tried like 6-7 times and all LOOKS good, but isnt...
I have a picture of how the setup was when i did work correctly, i am going to try that next weekend. If its wrong again ill do exactly like ur saying, great tip with the playdough, didnt think if that at all!
What about my theory with the IN valve being open that blocking the engine...?