Why do dohc engines have longer power curves then sohc engines for the same engine?

Question

Fir instance if torque is the same on both and drive the same but the dohc pulls no harder with same torque only for a longer perid of time.

both engines im refering too also have torque peak about the same place 4000rpm

Sohc revs to 5500 the Dohc 6000 with 40hp difference.

I kind of ment the general 2 valve sohc vs 4 valve dohc

Answer 1

Fewer moving parts produce more power. A SOHC also has more friction imposed on it then a DOHC. This also allows better performance. Having dual Cams will also allow a motor manufacture to be able to control the timing better. just about all of the variable valve timing cars have Dual over head cams.