Why do the sohc and dohc version of the same engine have peak torque at 4000rpm on both engines?

Question

Why do the sohc and dohc version of the same engine have peak torque at 4000rpm on both engines?

Answer 1

Engine have more than peak torque, hp numbers to represent their power.

Engines that have flatter HP and torque curve pulls better all through the rpm.  And having DOHC often accomplishes that better.

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