Guys why argue everyone is right, 4V engines are more efficient than 2V engines-correct statement, from a point of view. 2v engines are more efficient than 4V engines-correct statement, from a point of view.
The move to 4V overhead cam heads creates an engine that requires less displacement to achieve a certain horsepower (and torque) threshold at a certain (higher) RPM, this is more true in smaller displacement or shorter stroke engines where it is critical to get the mixture into the combustion chamber in a more consistant fashion (OHC engines in general do this better than OHV engines in this application).
A 2V engine is more efficient in larger displacement, longer stroke engines that are required to meet a horsepower (and torque) threshold at a lower RPM (OHV engines in general do this better than OHC engines in this application).
In a nutshell any OHC engine will produce more HP and torque than a similar OHV engine but that HP and torque comes at a higher RPM, so you technically need less displacement to produce the same HP and torque #'s, hence less displacement equals less mixture therefore less fuel but if you want that HP you need to rev the engine higher to get it, at the higher PRM you use more fuel.
An OHV engine will produce its usable HP and torque at a lower RPM so even though the displacement is bigger you rev lower so the engine doesn't use as much fuel.
Both configurations have their advantages and applications, so everyone is right, now go back to dreaming of a cruise in your new Challenger SRT8's with with some good tunes (Black Betty by SOIL is my favorite cruise tune) playing on factory stereo with the 50 Gig Hard drive (for your MP3's). Better yet make plans to meet up somewhere (maybe Montana or Oregon-8 State trooper cars to patrol the entire state) so we can see how fast we can go.