New cam...loud clacking lifters. ???

A Friend lent me an inspection camera today... I pulled three spark plugs and looked into three chambers... we saw nothing but three solid black piston tops... I'm ordering stock rockers, 901-16 springs, retainers, seals, keepers... does anyone know how many lands the stock valves would have? I will do the springs first, then the rockers to find out the real culprit!! Next winter I'll look at 302 heads and better manifolds...( If things hold together.) maybe a rebuild. thanks again....