This is a roof seam on a ’40 Dodge truck. Read how to smooth this seam and repair the rust
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Q. I am building my first street rod, a ’40 Dodge truck, but I am not sure what to do about the rusted metal and the seam in the front roof pieces of the cab. I would prefer to remove the joint completely and smooth the area, but I’m not sure how that would look since the two pieces fit together at an angle. I have a good MIG welder, but do not have a TIG machine. What are your thoughts?
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A. There are some potential problems with what I see. It looks like there is some significant rusting in the metal at the seam, so the best procedure is to cut away a strip of metal about 2 inches wide, centered on the seam, and then butt-weld a strip of new metal in place. Once tack-welded, you can hammer the contours until they flow together nicely, and you can easily blend the slightly different angles you have now. Of course, this will remove the rusted metal at the same time. You don’t need to worry about losing the strength the seam gives the panel. If you look at the roof of most cars and trucks, they have no reinforcement in that area, and they are plenty strong.
With MIG welding, there is some limitation on how smooth you can get the metal by hammering, but you can certainly get it close enough to finish with the use of a little plastic filler. The groove you have now is too big to safely fill with filler!
Q. What is the process of cleaning body metal of old paint, body filler, and primer like Joe McGlynn did in the Chopping and Sectioning DVD? I want to get my fenders and bedsides cleaned before I work on them. I do not have access to a soda or sandblaster. Also, I am replacing the skin on a ’67 Chevy tailgate. What should I use to treat the inside of the tailgate structure I will attach the skin to? It has some surface rust, and even though it will be covered, I want to know if you recommend treating it with a rust inhibitor.
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A. McGlynn used a variety of techniques for cleaning the metal on his truck. He used chemical paint stripper, and then a Scotch-Brite Clean and Strip wheel for a lot of it. That cleans the metal beautifully, and leaves a nice surface to work with. The Clean and Strip discs alone do a good job, but it does take time to cut through heavy paint and filler. He sandblasted some areas, but that’s not my favorite technique for a couple of reasons. One is that if the improper technique is used, the metal can be warped, and in any case, it leaves a rough finish that’s difficult to metal-finish. The strong point of sandblasting is that it can clean out deep rust pits in areas that are hard to reach any other way.
You may know there is a chemical dip process used for removing paint and rust. I like that technique very much, but it is expensive, and I’ve heard that sometimes the solution gets trapped in seams and can cause rusting years later if it oozes out. I understand that if the parts are thoroughly neutralized after dipping these problems are eliminated, but I don’t know how to tell if a stripper has done a perfect (or haphazard) job of neutralizing.
I’ve been using Gibbs Oil to protect bare metal from rusting, and I like it a lot. It’s extremely difficult to get products like motor oil or WD-40 out of every little nook and cranny, and reportedly with Gibbs Oil, even if traces are left on the metal, you can still paint over it without a problem.
For your tailgate, you really need to get every trace of rust off the surface, and then coat it with a good epoxy primer before you put the new skin on it. Products like Naval Jelly, which contain phosphoric acid, are good for light surface rust, and they leave a phosphate coating that helps prevent future rusting. CT