I had a rocker arm break on a car I had some time ago (like about 30+ years!!!)
It was a Hillman Avenger - sold as the Plymouth Cricket in the US I believe?
It wasn't a very sporty car but had twin Strombergs, dual valve springs (thick outer, thin inner) and a slightly "hotter" camshaft - I think it produced about 75bhp and 90ft/lbs Tq - than the cooking versions.
Anyway -
I took the head apart to replace the rocker arm and found an inner valve spring had broken and become wedged in the coils of the outer thus stopping it from compressing and hence the rocker broke.
No other damage at all but I stripped the head, re-ground the valves and de-coked the head (remember those days) while I was in there. All very easy in those far-off 'simple' days
The valve spring thing is probably not applicable in this case but it just got me remembering...
Cheers
Dave