I am close to having the bottom of my Challenger ready for paint and have a question about the seams. I have a number of lapped seams where the 2 pieces of metal have a small gap between them. Do you guys put a sealer or some type of caulk on this or just paint as is?

Thanks

I use seam sealer. It keeps water and debris from getting in between the pieces and rusting.

I don't think there was any under the car when new, it's all inside I think. It's not a bad idea to do I guess for extra protection.

I did'nt do it on my cars but I don't drive em in the rain.

I just painted the bottom, no seam sealer.

I am also at the same point on my 70 Challenger. I finally removed all the dealer undercoating and have the underside primed in self etching primer. I did spray a rust encapsulator inside the frame rails (and fabricated sub-frame connectors)once I replaced both quarters. I am putting seam sealer around the rear wheel wells from underneath, but that is about the extent. The remainder (majority) will be applied from inside the trunk and interior.

Seems like cheap insurance to me. As long as you are right there, how much more time can it take in returen for the peace of mind it will give you?
I intend to seal every seam I can possibly get to as I put my 70 GTX back together. I don't plan on driving in the rain all the time and I am in Calif. where we don't have salt.

I would leave the bottom flanges open so condensation can run out and not be trapped.

Sheldon

I would leave them open and rust proof after.