Hi all,

How do the two middle vent parts I have marked on the drawing seal against each other? The drawing is from a 71 FSM and my car is a 70 but I imagine they would be the same on this.

I noticed a black powdery substance in that middle vent underneath the vent part that rotates. Is that the remnants of a seal that used to be there? The part on the right is a flat piece of metal riveted to the part immediately next to it further on the right.

Thanks

The black residue you're seeing is either the remains of the foam or what's left of the black "suede" or flocked finish that got applied to the inside of #31.

Additionally, the chrome center vent fits inside 31 and is held by 32 + 33...

The area where your blue line touches #31 is (was) a foam which not only sealed to part #30's metal face (which you ID'd above) but also pushed slightly up against the chrome center vent. This foam, due to age, typically disintegrates and needs to be replaced. I don't know if buying the replacement for #31 would provide it or not.

If memory serves I have a #31 untouched (because the foam that's on there will barely accept looking at, definitely NOT touching) so I'll provide pics later.

When I redid my vehicle and a couple of friends, I re-built the foam using closed cell foam strips that I cut and shaped to fit. I don't think I have pictures of the finished product, but I'll check and see.

FWIW

E

Mike, I just restored mine last month, what was sealing those two pieces and most of the rest of the heater box was 1/8th to 1/4" foam with a sticky backing. The closest thing I could find from the hardware store was the peel and stick draft proofing for older doors and windows. In some places I just used RTV sealant as it will probably be another 40 years before the next guy gets in there to refresh.

But that particular join your asking about could use 1/2" foam strip as the bellows behind it probably isn't very springy anymore and you'll need the thicker foam to keep a seal. Somewhere in the archives is a step by step heater box overhaul, can't find it at the moment but it is worth the hunt.

Chris

Mike,

Nothing "holds" them together except the pressure of the heater control faceplate attached to the dash. The two metal tabs/ears on the bellows on #30 act as a centering function as #31 moves to it. The dust you see is the remains of the old open-cell foam gaskets used throughout the system. Try to find some thin closed-cell foam for any new seals. I found some sheets of fragile item protective wrapping and cut gaskets/seals to fit various joints. Hope this helps.

Jim

E,

Thanks for the idea on the foam pushing against the chrome. That might be what filled in the gap that I wound up with. Below are pictures of what I did but the gap at the bottom after installation bothered me a bit so I figured there was more to how the foam went in than what I had guessed. I would enjoy seeing a picture of the vent you have if you still want to post it.

Chris,

I hadn't thought of the bellows as being springy because they are so stiff now that it hadn't occurred to me. With your search idea I did find a heater box overhaul thread (listed below) I don't know if that is the one you had in mind, it is a good one.

Jim,

Thanks for the idea of protective wrapping, that opens up some possibilities for materials to use especially if I end up refreshing moving parts of the duct system.

Mike

Gap visible (need more foam tape?), foam tape is not sticking out far enough and is offset:

What I did that wound up leaving a gap (foam tape spray painted black later to hide better):

Foam tape I used (I glued in with glue gun glue to make it stick better):

Typing in heater for the search (instead of duct like I did) yielded other threads on this in case someone else finds this thread and wants more info:

Heater box overhaul:

http://www.classiczcars.com/forums/thread23409.html

More info:

http://www.classiczcars.com/forums/thread46605.html

Edited December 25, 201212 yr by Mikes Z car

Don't forget RV repair shops when looking for closed cell foam. That's where I found it in a whole assortment of widths, AND thicknesses as well as several combinations thereof.

E