I was getting ready to pull the engine out of a 65 series Chevy truck for a hot rod project. I drove the truck home a couple of miles. It didn't overheat and oil pressure was over 50 psi. It had a miss in it but since it hadn't been in service for years I pulled the plugs for a compression test. I found the #5 cylinder exhaust valve pushed all the way open and stuck there. I pulled the rocker arm off and tapped on the valve thinking it was just stuck open, the spring did not look broken. It did not try to return open at all, it just went down to coil bind, I was able to pry it up only a little but not back where it should be. The pushrod was not bent but was high and it did not tap down easy either. The lifter was pushed up and it would not go down or even try to follow the cam. I've never seen or heard of this. Anybody have any ideas what I can expect when I pull it apart?