If you want to run an 8 volt battery its simple enough to build a 2 volt voltage reducer with 3 power diodes in series. Check the maximum current draw, then use diodes that are rated for at least double that. Ex: 70 amp diodes are about $5 each on ebay. I don't see any need myself to use anything besides 6V but if its your car, do as you want. Maybe if you have a leaky carb the 8 volt battery will seal it up?
