Undercoating

[shoooter]

I did a search and couldn't find the answer I was looking for. My trunk pan was replaced before the car was painted but he didn't paint the trunk(its getting painted)or the underside of the car. the car has undercoating everywhere but the new trunk pan. Do I paint this or use undercoating to match the rest of the car? What brand works or can I just get some stuff in a spray can and do it? Thanks for your time

[burdar]

Was the undercoating factory applied?  Does your car have hood insulation?  Factory undercoating was part of a package that included hood insulation.

The factory sprayed the undercoating shorty before the engine/trans and rear axle were installed in the car.  The gas tank and muffler heat shields would have been installed before the undercoating was sprayed.  If your car didn't come with full undercoating, the trunk pan would have recieved a little undercoating overspray when the wheel wells were being sprayed.(all cars came with the wheel wells undercoated)  If your car had full undercoating from the factory, the trunk pan "could" have had more undercoating but most of it would have gotten on the heat sheilds. 

What you do is up to you.  If you decide to undercoat it, don't use the spray can stuff.  Use 3M body schutz or buy RestoRick's undercoating.   

[Giveitawack]

I have understood it this way:
The body was dipped in a flat grey primer. Waterbased. About a foot up on the body. When it came out of the dip, paint was rinsed from the outside with a water hose. The dip line should be visible inside the quarter panel.
So yes the trunk floor should be grey primer. And the inside of the trunk of course body color.
The underside only got overspray from painting the rockers, quarters and rear panel.
Full undercoating was an option (anyone got the code?) Without this option only the wheel wells were coated with the fuel and brakelines and rear axle bump stop in place.

[burdar]

My original muffler heat shield is completely coated in undercoating on the bottom side.(full undercoating car)   I believe the inside of the quarters were undercoated "before"  they were welded to the body.  There is a picture somewhere of a factory quarter that was cut off for replacement.  There was undercoating in areas that would have been impossible to reach with the quarter welded on.  If the car came with a rear swaybar, it was also installed before undercoating.  There is a great picture showing this in the reference pic section.

Full undercoating is J55.(in 73 anyway)
   http://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1973/73_Challenger0015.jpg

[shoooter]

  if the wheel wells were under coated would you paint them me body color over the undercoating? Or would they just be left under coated. Would paint even stick over the stuff?

[Giveitawack]

Body color first. Then undercoating. No paint over the undercoating. Think the undercoating served as a blackout as well.

[shoooter]

Body color first. Then undercoating. No paint over the undercoating. Think the undercoating served as a blackout as well.

Does the undercoating go on the backside of the fender too? Maybe I'm missing part of the front wheel wells and you shouldn't  be able to see the fender back

[burdar]

Yes, the undercoating was sprayed on the back side of the fenders. It protected the fenders from being dented from rocks.