Let us assume all things being equal other than the weight of the camshafts themselves. Is more torque required to rotate the camshaft of a large displacement V8 car engine than a small displacement inline 4 cylinder car engine?
As Fred has said, all other things being equal, the camshaft with the higher inertia will need more torque.
However, this torque is insignificant compared with that required to open the valves. This isn't dependant on engine capacity as such, but a larger engine (or a higher rated engine) will generally require more force to open the valves.
There's not nearly enough information about the two engines (large displacement V8/small displacement I4) to make a comparison here, you'd need design details for both.
brewnog, I don't have the specifics on these engines other than what I have given. But I don't need an accurate answer just a general answer will suffice.