Different camshafts. Why?

[sketchman]

I know what a camshaft does, so I assume people use different ones to open and close the valves at different times that stock. Also, DOHC motors make more power than SOHC ones of the same design.

So, why does having a different camshaft, or 2 of them, add power? If DOHC engines are better, why are SOHC ones made? And if a different camshaft can make more power than the stock one, why isn't the better one the stock one in the 1st place?

These are probably simple questions, but I'm confused.

[FestYboy]

emissions and fuel economy plus logistics equals cam selection along with valvetrain type

it's all about the beans

[muscle_Car1]

I know what a camshaft does, so I assume people use different ones to open and close the valves at different times that stock. Also, DOHC motors make more power than SOHC ones of the same design.

So, why does having a different camshaft, or 2 of them, add power? If DOHC engines are better, why are SOHC ones made? And if a different camshaft can make more power than the stock one, why isn't the better one the stock one in the 1st place?

These are probably simple questions, but I'm confused.

DOHC is better because the the intake & exhaust cane be timed differently.
SOHC are still made because they are cheaper to produce.
Emisions, fuel economy & powerbands not suitable for daily driving are reasons for different camshafts

[jglutz]

Everytime a a valve opens and closes and the fuel is sucked in and the exhausted gas is pushed out....horsepower is sucked off the crankshaft that is not sent to the wheels.

Engine designers try to design cams so that the ammount of horsepower lost in the cam/valve train is minimal as compared to the flywheel horsepower.

Performance cams TYPICALLY create better breathing....more fuel/air may be sucked in and more area is provided to push the burned gas out. This all comes at a cost...though the horsepower at the flywheel may increase...more horsepower was sucked off the crank to operate the vales. Result: Performance goes up...MPG goes down.