This like the no replacement for displacement argument in that no matter what you do to a 4 cylinder you can also do to an 8 cylinder therefore the 8 cylinder will always win. As for OHC vs. OHV there really is no significant power advantage if it is a SOHC vs. OHV 2-valve arrangement. BUT a ported/polished/extrudehoned/etc. OHV 2-valve head is still no comparison to a DOHC thats been treated to the same mods. Now there are OHV 4-valve setups but they have not been used very much for high rpm situations because of the heavy valvetrain required plus they cost mucho dinero; they are used in low revving diesel applications though (ex. Duramax diesel V8 in GM fullsize pickups). DOHC is so good that theyve been banned for use in NHRA Top Fuel because of the superior power vs. the OHV Hemi arrangements that they use now. So ultimately with all things being equal the DOHC set-up is superior. But for my budget Ill stick to OHV feeding a nice V8.