defrost on windsheild

[kmyles]

When I change from the vents on the dash to the def I don't get the same volume of air on the defrost. I still can feel air blowing elsewhere. It's all put in the car and the heaterbox is a tight squeeze as it is. What can I do to look into the problem?

[dodj]

If your car is similar to mine, there is an air gap in the plenum that goes to the defrost from the heater box. The gap in my car is about an inch. Every Challenger I have looked at has a significant gap there.
Look at the pic posted by iNTP a couple threads down called 'heater box and defroster vent.'