[OrrieG]

It needs to be enclosed with a small drain hole on the bottom. Something most are not aware of (I wasn't) is that there is a factory cleanout at the bottom of the firewall/air plenum. When I first saw it I thought it was a repair someone had made, but the FAM show it. The intent is to unscrew the flap and clean out all the leaves, dust, etc. that comes in thru the cowl vent. If you don't, a dam is created that holds water and channels it to the lower hinge pocket and everything rusts out. When I opened mine there was probably a foot of old dirt, leaves, etc. I left a corner slightly open to drain water. here is a photo.