>>>*There is almost enough information in the photos to diagnose the cause, not quite.

Note the piston markings, the valve stopped moving first, contacted the piston. Additional motion moved the valve further into the bore with successive strokes until the valve completely jammed.

It could be the guide was just too snug, or lacked adequate lube. It is possible the valve was drawn into the piston during installation, bending it it the cam was not perfectly in time at install.

But something jammed the valve first, or the valve released, that isn't the usual damage we see from a weak spring or from excess tension.

Coil binding normally results in failure at the keeper, although it could be that a valve lock slipped too since damage from pressing against the guide shows very high up the stem.

This indicates the valve was finally open much more than one would think possible if the locks stayed attached.

These heads will easily handle .450" lift and more if the installed spring length is 1.600" like it should be....*EB