Defrost duct

[Gregk]

Hello everyone this is my first post.
I have a 78 gmc that I'm trying to get the heat and a/c working in. After replacing the leaking heater core and getting the hvac box bolted up, I noticed the bottom of the defrost duct doesn't line up with the top of the box, there's about a 1 inch gap as you can see from the photos. I'm not sure what I'm doing wrong or if there is a missing part that should go there. I know I could use tape to seal it off but I'd rather not do that if I can help it.

Any advice would be appreciated. Thanks .

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[Originalthor]

I had the same thing and made this. Worked way better.

You must be registered for see images attach

 

[Chevy 88]

You could always try expanding foam. It seals up large gaps really well, and you can easily trim it away as needed.

You really need to follow the directions on the can though, or things can go bad.

 

[mxer147]

Mine looks similar, I am considering adding some plastic attached with rivets and the silver duct tape. Might work on that tomorrow and if I do I will post a few pics.

 

[ali_c20]

Welcome from Austria.
Same on my K5, I made a sleeve out of abs plastic.

 

[cutoffkay]

Welcome

 

[Gregk]

Thanks to everyone who chimed in. I ended up using foam all around and it seems to be working so far.
I don't understand how the guy who designed this thought it was a good design.