Cam making engine work harder?
To answer your question, no. A cam should give it more power, which would mean the engine would not be working as hard for "normal" driving. However, cams with alot of overlap will idle a bit rough, which is known as cam lope. This is normal, and preferred by some so everyone will know there is a cam in it. In fact, some people actually buy a cam for no other reason other than the sound (which also results in "shake" at idle). Cams with lift higher than the stock cam will work the valvetrain harder, but this should not be confused with the engine laboring (ie working harder). Tuning will minimize the "shake", but will not eliminate it completely. It's the nature of the beast.
To answer your question, any time you make the engine produce more power you are putting more stress on the components in the engine. If that is what you mean by working it harder then yes, a cam makes it work harder. As DaveX said though, when driving normal a more powerful engine will not have to be pushed as hard. How hard you push your engine is up to you.


