not good

1968FormulaS340 said
If you can easily open the valves by pressing on the springs, your springs were done years ago.

Probably floated the valves allowing that pushrod to jump loose and get beat up.

I had a chev 350 that had springs that were so dead that the valves would float at 3500 rpms.

X2 and I had a 350 Chev that the springs were so bad on it floated at 2000 rpm. I could push a couple down with one finger, LOL

OwdKasd said
I agree with this possibility except It should have been obvious that after "getting on it" a miss developed. It would have been instant. I guess pulling the head is gonna be necessary.

He said it was running badly. No need to pull the heads to change valve springs.