Camshafts, do they work?
This might sound like an odd question, off course they work, aftermarket camshafts causes air and exhaust valves to open for longer and push them further down. This will cause the engine to produce more torque and with force feed induction vehicles less inlet manifold pressure and more horsepower.
But this is only the end result, its only after the increase in lag that one starts to smile on how much faster the vehicle is. There is a catch, when you increase the duration and push of valves you are also increasing lag at low rpm.
Regarding low to mid rpm situations only, to make power on petrol engines require in the following order - air, fuel, compression, spark, exit (exhaust), but when valves that are responsible for air opens for longer, the engines compression or turbocharger can not somehow overcompensate for the decrease in air pressure. Technically, air volume has increased but without a certain amount of pressure less air is initially being pulled by the engine. Its velocity vs volume, a drawback which ever way you see it that when decreasing camshaft profile increases response but decreases peak torque and vice versa.
There are expensive ways of overcoming this, variable valve timing engines allows two cam profiles that switched between the two after a certain rpm range like the Honda VTec range and Nissan's SR20ve engines, twin charge configurations such as supercharger symmetrically charging a bigger turbo, sequential turbocharging, etc.
As for turbocharged vehicles I am more familiar with, even today there are still a lot of gimmicks when it comes to camshaft advertising, claiming you can make power everywhere, but I am yet to be in a car or see a dyno plot that shows an increase in low and upper horsepower. The reality is all dyno plots show an improvement from mid to high rpm but overall push the torque band higher up the rpm scale, its not any different to installing a bigger turbocharger as you get the same effect but with denser air and a bit more power.
Overall in my opinion, which ever way you see (unless your willing to spend big coin, as mentioned above) it there will always be drawbacks, take also into account the cost of installing and tuning, the increase in safe rpm but decrease in engine life. I am a lone wolf when it comes to the idea that i believe you don't need camshafts, as there cheaper and better ways around it, cams are not what sellers make them to be, but I have nothing against people who do own them.
