I have a popping coming under exceleration from under air cleaner at carb. Is it bad valve or lobb on cam shaft any ideas on how to figure it out?

 

I suggest to try to determine which cylinder(s) is the cause.Scope test is good place to start if possible, if not or scope test is inconclusive.Next perform power balance to determine weak cylinder.It should show up.Remove spark plug from suspect cylinder and inspect.Check compression if its below 50 psi most likely a valve isn't closing,if it is above 90 psi check remaining cylinders.To do it right throttle should be wide open.Lowest reading should be 80% of the highest.If effected cyl.is highest exhaust valve may not be openning.Remove valve cover check for broken valve springs,bent push rods,worn or broken rocker arms.If nothing is obvious, kill ignition and electric fuel pump if present a crank engine see if intake and exhaust valves travel up and down the same amount.If they do the cam is not the cause.Techs all have their different ways to diagnose drivability this just one.Hope it helps