Given the minimal amount of splash shielding in a stovebolt engine compartment, there was less of a chance of an ignition system drowning out when splashing through a puddle or fording a creek to get to the next pasture if the coil wire was pointing down. Some of the Brit sports cars mounted their coils the same way for the same reason. Spit on the sidewalk 3 blocks away, and a Jag XKE would drown out! Of course, the Brits drink warm beer because they've got Lucas refrigerators!
Jerry