There are many good reasons to buy a 4V 308. First off the obvious, 4 valves per cylinder(extra HP). QV means Quattrovalvole. English translation = 4 valves. Also it came with 16 inch wheels, slight interior updates including steering wheel and aerial button changed to a switch near the e-brake, more symbols in the gauge cluster area for the warning lights(battery, fan, defroster) seperate drive belts for water pump, alternator and compressor, hood vent for additional cooling, latest water pump bearings/seals, later models have Lambda Control(including frequency valve, ECU, pressure damper). The QVs also are worth the most of all 308 models. Plus they had rust proofing. Pulse air injection (uses exhaust back pressure/reed valve) replaced the traditional belt driven air pump. Later QVs came with a Single 3 way catalyst vs. the 2 catalysts of previous years(this included 83' which is the first year of the QV).
As you can tell I love my 1985 QV. IMO they are the best. Now this is where I disagree with others. Unfortunately, many QVs have been neglected. Since they are known as the most reliable 308 many owners didn't maintain them as well. (also since they are slightly newer some items weren't addressed from age as older cars) Nikasil liners also came on later QVs.
If you have any particular ?'s send me an email.
I appreciate the information you provided, I recently purchased a metalic black 85 QV and have loved every second of research on the model. I would also appreciate any additional information you have discovered that is very valuable to be aware of while I continue to enjpy the experience of owning the car!