I wonder if it would not be better to have the louvres only on the sides and at over the air intake for the heater/aircon.
This has always been a bit a conundrum for me as I have exactly that louver configuration. No louvers over the engine but I do suffer with corroded plugs. Obviously louvers might let water into the engine bay but I don’t buy into the mainstream belief that they are responsible for corroded plugs. Many Fords suffer with corroded plugs too and they don’t have louvers either and often have clever designed engine covers.
The water sealing around the cam cover and plugs lead is really very good on my engine. The plug caps have a super tight triple finger environmental seal and there is a 10mm high up standing on the cam cover around the plug cavity. There would have to be quite a deep puddle of water sloshing around to breach that!
One of my corroded plugs despite no louvers
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My money is on high humidity noxious internal combustion gases getting past the cam cover seals and causing condensation to form on the plug surface which causes the corrosion. Perhaps on a cold day when an engine block cools after a run the plugs on top would tend to attract surface condensation from the high humidity cooler atmosphere trapped around the plugs?
Here is a pic of the underside of a Duratec cam cover (not mine).
You can see the seal paths around the plug chambers where the cover seals to the head. Whilst this type of simple seal in a plastic housing would prevent the non-pressurised engine oil escaping it would not take much of a pressure differential for gases to escape into the plug cavity.
Just a theory………
