I just replaced my heater core and blower motor. I noticed the defroster vent didn’t mate up with the blower port for that vent at all so I used some aluminum tape for duct work; this is not your normal duct tape. It’s like thick aluminum foil with a sticky backing and it works great to seal everything up!!

http://members.cox.net/1970chevelless/1970chevelless/images/heater/DSC02913.JPG

Some picks with the enter fender removed…..
BEFORE

http://members.cox.net/1970chevelless/1970chevelless/images/web/dsc02863.jpg

AFTER

http://members.cox.net/1970chevelless/1970chevelless/images/heater/DSC02914.JPG

Mine didn't contact each other either, I figured it was designed that way for some reason.

Oh and did you notice that your new blower is only a 3 speed now instead of a 5 speed motor like the original was? I noticed that when I changed to the new blower motor on my 70. Didn't bother me though because it keeps the top 3 speeds and dropped the first two lower speeds. Definitely blows just as well on the top end.

I could be wrong but there is only one positive lead on the motor. It doesn’t really have any speeds. It just runs speed wise volts per RPMs. The more power the fan switch puts to the motor the faster it goes. You might want to check your switch.

You're not wrong, the motor speed IS controled by the amount of voltage supplied from the speed control resisters.
Good idea to seal up the air leaks :thumbsup:

That foil tape works great for a lot of different things, I have some so heavy it has to be cut with a hacksaw (not really but close :D )

Hey Nialator! Funny you should post this info, because as you know,I was finishing that same project, I wondered about that gap between the defrost unit and the heater box. I wasn't sure if it was intended by GM, so I put a piece of foil backed jute matting around mine, but didn't seal the back up real well. It seems to work ok and the heater is in tip top shape thanks to info from everyone. One little FYI, everyone is aware to be careful when reinstalling the heater hoses to the core in and outlets, so to help, just dab a little anti-freeze to the inside of each hose before you slide them on, it makes it easier and will prevent breaking the pipes. I also used spray silicone.
It's actually warm in the Fun 71 and no mist blowing through the vents!!!:beers:

Thanks 'fun 71' I know you where thinking about doing this so this is how mine turned out.... Still have a few more wires to hook up but I had to share this with someone. Definitely need to get the black dash pad, but its getting there.....
Actually the entire inside is going black, see what a nice job the heater core did on the passenger side…..
http://www.beasonfamily.com/images/dash.JPG

Ummm,

If I were you I'd remove that tape. My '70 has the gap as well---they all did.

This "gap" serves (3) functions;

1) It sped-up assembly of the cars, 2 separate pieces rather than trying to duct furnance piping under there ;)

2) Serves a "kiddie toy trap". Anything that would fall down the defroster vents like toys, candy, pencils, etc would be more easily retrieved by crawling under the dash and pulling it out from the top of the airway vent (yes there is a little grill guard on the fiberglass distribution duct) right under the defroster "y" pipe. If this was sealed or one piece, you'd never get the stuff back.

3) Provides a temperature differential. Take a close look at the defroster ducting, it is verrrry flimsy plastic. It can not take the heat that is generated from a closed-circuit ducting network, it will warp. This gap allows the duct to "catch" the output of the air, but doesn't create a sealed chambered.

Just for your information. No disrepect intended.

None taken, I value your option as I do everyone’s on here. I think you are correct on several of the points you made. I personally pulled 4 lighters from this cars duct work… but I don’t smoke so this shouldn’t be a problem for me.

My ‘Y’ pipe is in good condition and is made from quite thick material. None the less you are correct; all 5 – 70 Chevelle’s I have owned had the same gap. I live in Nebraska and the winters can get bad here. The car will probably never see this weather as the mater of fact I may never use the defroster but if and when I need to I want all that air getting to the window.