I would think you have a possibility for a good product there. Tons of people use foam plugs for many purposes. Cowl plugs for airplanes, exhaust plugs for racecars and motorcycles. They keep out water, humidity, rodents, etc. during storage and cleaning.I was just trying to see if someone already made a product like this. some people dont care if their motor isnt clean or spot free but that is what i enjoy doing is detailing so i like to keep it perfect looking. air compressor works fine for heavy water but if the underhood is hot it will dry alot of the water fast leaving alot of water spots.