I sealed off the air inlet to the carby, and poured a bucket of water into the snorkel to check it out. I was surprised how may leaks showed up.
The main concern is the pre-heat air flap, which produced a steady stream of water. The next worse leaks were at the dust spinner and the factory flange to the mud guard.
I still haven't worked out a way to seal the pre-heat and also keep the vehicle road worthy, and it needs the heat to run properly in winter. I did try a brass reducer and removable plug, but it restricted the air flow too much.
I am toying with the idea of running a flexible steel steel pipe in parallel from the spinner outlet across the headers and up to the pre-heat .