470 runs out of steam at 5100 rpm

d55dave said
In my experience ( I have had this happen twice ) the problem is either incorrect valve springs for the cam so the valves start to float, or fuel starvation and or vapour lock caused by too small of a pickup or fuel line (or the pick up is clogged). Todays crappy ethanol filled fuels exacerbate this problem.

I have confirmed spring pressure and install height with Comp Cam! Both are at there recommendations! I have 3/8 line from fuel tank to carb, regulated to 6.5 lbs! I do not believe it is a fuel problem as I feel no stumble at all, just no more pull out of motor!