Ratty tat tat under the valve cover.

[PANAVIA]

If you have gone this far, you should complete the job. - clean the valves , get some nicer roller lifters, roller rockers etc.

Note: when we see scorpion rockers, we remove them and put on Comp cams or Ford Racing / Cranes. I would also check valve spring pressures , open and closed. -- if the lifters are stock roller lifters from ford , it could be - they may not be up to a heavy spring pressure from the head , which did them in.