[LT7A]

I found this thread from reading another one and since it's current I thought I would post here as well. I give quite a bit of consideration on how to bring cooler air in for the motor (and let heated air out) and have read a bunch of threads on different forums.

Regarding the idea of contamination of the cabin air, I get the idea, but a good setup should keep a problem from happening IF, and it's an important if, there is an airbox that is sealed to the firewall. Were someone to just cut a hole in the firewall to let cool air in near the carb then there is a high likelihood of contaminating the air that the heater/AC draws from. If the hole is sealed to the airbox/carb, then I could see that some gas fumes could conceivably meander through the air filter, into the cowl trough, and into the cabin. But unless you're running the heater with the engine off, there's not a way to draw contaminated air in. As long as the heater/AC and the engine are both running, both are a source of vacuum and have an sizable amount of outside air to draw from based on the size of the plenum.

With regard to rain and washing, I think if the hole was above the floor of the cowl trough you'd be alright. Maybe screen it to catch big drops, but I would imagine that whether it's intake air or AC/heater air that it will lose the water droplets when it turns the corner to the intake area.