okay my old one sort of disintegrated so i got a new one and i dont know what the procedure to installing it is....its easy seeming except for the fact u have to get some screws into very tight spaces which is next to impossible......

any tips?

 

I did this last summer on my 66. The cardboard plenum dissolved in my hands when I went to check why defrost lever wasn't working. The replacement plenum I used is plastic and a big improvement. Yeah, the four screws that hold the plenum to the heater core box are hard to get at. I alternated using an open-end wrench and a little ratchet set and just kept struggling until I got them off. Once I slid the new plenum on, I just put back the two easiest screws to get at and left it at that. Seems to be holding on.

 

ok so its just going to be a hellish install nothing u can do about it eh? haha

better get to work.....

 

whoa, when i replaced mine..... i didn't see any screws, and i didn't mess with any screws.......... ut oh.

 

well i got all the screws out....but the thing totally dosent like fit at all....its very weird.....it wont even slide on.

 

Yeah, I had to pull off some insulation from either the firewall or from behind the carpet, I can't remember which exactly, to push it in far enough to match up. The new plastic plenum looked to be pretty much the same size as the cardboard one (what I had left to compare it to anyway) but for whatever reason, it wouldn't align with the metal heater core box. Once I got the extra half-inch of clearance, I was able to slide it over fine. I got the replacement plenum from California Mustang and it was about $30; I think Mustang Depot was a lot cheaper, like $18, but it wasn't clear if all the levers and damper stuff came with the one they had. What amazes me is that this part for a Classic Mustang was made in China (I guess it shouldn't, everything else is). good luck.