One concern on the late model 235 engines with the big cam bearings and the cast iron cam is clearance between the connecting rods and the camshaft. The cam has flat spots cast into it between the lobes so the rods don't hit the cam in normal operation. If the cam gets out of time there can be connecting rod/camshaft interference. Pistons and intake valves also run with a bare minimum of free space, so under some circumstances it might be possible for cam/piston contact with a badly out of time cam.
Jerry
Haven't heard of these specific instances, although as you say it's possible. In the words of a reputable vintage Chevy parts supplier in business for a long time when asked about whether the 235 is an interference engine: "No, there's enough room to sleep in there." (!)
Bent pushrods is another issue. Maybe valves floating at high RPM? Probably not caused by valves contacting pistons or catastrophic damage would likely occur.
Lots of theories! Many of you probably have practical examples to share.
