My 82 TA has headers that generate a lot of heat I have wrapped them and it helps alot but their is still alot of heat generated through the floor so im thinking of installing the foil backed padding under the carpet then putting it back. It should also help deaden noise. Has anyone done this and is there anything I should watch out for iI would like to know before I get started the padding is approx 5/16 thick.

 

Redraif and I did her whole car with it while we replaced the carpet. The only problem we found was in doing the area behind the rear seat, as the extra thickness made it more difficult to lock the seatbacks. Her car is just a V6, but you don't get any heat through the floorpan and it cut down a lot on road noise inside the car. I think there are some pics of the install on her website:
http://www.cardomain.com/id/redraif

 

Did you glue the padding down (foil side down I assume) and do you do anything on the seams? I see Summit has a glue with their padding.

 

We glued it with 3M spray trim adhesive, and covered the seams with foil type duct tape. Worked great.