Question about backdating heat on 88 3.2

[Snitzler]

I would like to backdate the heating on my 1988 3.2. I have a 930 left side hot air duct and the outlet is around 2.3” The air distribution tube is 2.7” diameter. How can one piece of flexible tubing work between the two different outlets. What am I not getting? I don’t have one of those black boots that is between the tube and the air duct, does that reduce the diameter of the air distribution tube like on the second picture?

[ian c2]

One end goes inside , other end goes outside .
With reducers you make up the difference .
It might be more elegant to split the difference at both ends ...

[SpyderMike]

Here is how I did my 1985:

so this is how a backdate project starts...

Post 30

You can buy reducers to take the heat exchanger diameter down to the flex tube diameter. I then used a 2.5" aluminum pipe to couple the flex tubing to the reducer. It has been working fine.

[gtc]

The easiest way would be to set it up like your second photo. There should be plenty of people with the stock rubber coupler laying around. I bet I still have mine somewhere.
I wouldn't bother with the SCAT aircraft hose. It doesn't fit quite right (it is 2.5" or 63.5mm and the corrrect diameter is 60mm) so it is a hassle in the long run. If you look through PET, you can find a long section of heater hose for a reasonable price... I believe I have found them in the 911 SC catalog.