'70 Cutlass non-A/C lower vent air plenum. Each side has insulation affixed to the outer wall inside the lower vent plenum at the footwell. Removed the grill to the lower footwell plenum vent, reached inside, at the bottom of the plenum is 50+ years of accumulated debris. Vacuumed debris out. There appears to be an irregular opening at the bottom inside the lower vent plenum. Is that opening to allow for rain water to flow out from above at the cowl? One vent side has a small handful of caulk at the bottom of the plenum, and I can't determine if the caulk was to plug the opening in the lower plenum, or not?

Any guidance would be appreciated. Thanks in advance.

 

2nd image is of the bottom of the driver's side lower vent plenum.

 

The hole in the bottom of the plenum is for drainage.

 

Thank you for confirming.