Ouch Man!
I have seen that...once. I floated the valves (7200) on a roller 318 and it had stock rocker valve train....lifter was still in the bore (roller cam Spider held it), but I jammed a pushrod through rocker just like that.
I removed the intake, inspected everything, put a new rocker and pushrod in and everything was ok.
As for WHY it happens.....do you have adequate springs for your cam?
What casting heads do you have, and are they cut any? If your block is decked and the heads are cut, your pushrods may be a bit too long now....just trying to findout some info.
Coil Bind, and over revving are sometimes detrimental.
Hopefully yours will fare well.
Good Luck!
