Those of you boxing the stock chassis, what are you doing with the inside of the rails? Are you shooting them with weld through primer? Leaving the stock paint? Leaving them bare? I'm prepping my 60 frame now and was thinking I'd just shoot the inner rails with weld through primer.

 

I did not do anything to the insides. But since I am 75 years old, and this is a fairly dry climate here I think they will outlast me before rusting out.

 

Unfortunately that's not an option for me as I'm in Denver and we get plenty of snow and rain.

 

I’m in a similar climate here in Idaho and I’m in the process of boxing my frame. I pressure washed the frame and knocked all the stubborn debris off with a wire wheel. Then I coated the inner channel with POR15. In my haste, I forgot to tape an edge for welding, so I went back with a flap wheel to clean up the welding surface. Then I did the weld through on the back of the plates and along the edge of the frame.
That being said, my frame paint is completely hidden by light surface rust and dirt. I don’t have any serious rust, just frame patina. My thought was that the POR15 will help stop the cancer in the inner channel where it’s tough to get with a grinder. I had considered having it sand blasted, but I couldn’t seem to get the time to drive it an hour away. I’m confident the rust inhibitor will stop any spread and since it’s in an area that will see little to no sunlight it should hold up a long time. As a added level of protection, I will likely paint over the POR15 when I’m done with frame modifications. This is why I chose to plate with holes.