By definition a zone 8 location would have low temps in the teens at the coldest. My first reaction to your question was "no", but I have a friend in Nipomo who has a seedling cherimoya, seed from Costa Rica, that survived 19F as a grown tree. It may be that the rootstock of the tree or the source of the seed for the variety that you grow could make as much difference as the scion you have on top.
That said, if you pick the perfect location, with great drainage and a southern exposure, up against a wall or other structure, then you could have success. I have found that a top over trees does as much as or more to protect them than do walls surrounding the tree, so you may consider keeping the tree small and build a structure that can hold a ceiling over the tree in the winter.
Good luck with your experiment!