The rear roof seam on the 56 has some rust holes . Not sure how to seal them up . I have ground the seam and shot rust cutter into it . There is no way to weld up the holes . I am thinking I should fill the seam and sand smooth , then paint . If I do this then I think the seams that run from the door jam to the hood should also be filled . Right, wrong , or better ideal ?

 

How big are the holes, can they be drilled out and plug welded?

 

This is what I'm using on all the seams in my cab. It will also fill pin holes in rusted areas in the seams.

POR PATCH

 

the holes are small but they are deep into the seam where the two peace's meet inside the cab. can the por patch be painted over ?

 

Yes you can paint over it. It's basically just a thicker POR-15. If you are worried about it they sell a primer (tie-coat ) that is made to adhere to cured POR-15. But most people just scuff the POR-15 and paint over it.

If the rust is deep in the seam I'd paint the seam with POR-15. That paint is thin enough it seeps right through the seam. Then apply the POR-patch over the POR-15.

 

I am not familiar with the POR-15 patch product but I will comment on any product that is advertised as "remaining flexible" after being applied. If you are going to apply this sort of product to an area that will ultimately be painted and visible, then you should be aware that it will expand and contract at a different rate than the metal around it. What this means in the end is that you will either have a bulge or an indentation in the paint when the temperature is hot or cold. Worst case is that the paint itself will crack and flake. If you notice that in the examples that POR-15 uses, the patch is not applied to exposed surfaces.

If this sort of fix seems right for your situation then I would highly recommend using a 2-part product that sets chemically and does not "air-dry". Catalyzed products are far more stable. I personally use 3M 08308 Heavy Bodied Seam Sealer in many areas on trucks/cars where gaps need to be filled. It works especially well in the drip rails where seams come together...poor quality seam filler used by the OEM on the 56 F100s has resulted in many 56 cabs being scrapped long before their time. 3M 08116 Panel Adhesive is another product that may work for you if you choose to reinforce the back side of your repair area with metal. Good luck and post some pics of your project.

 

POR-15 remains flexible when it's cured. POR-Patch is just a thicker POR-15. I'm going to coat my entire 54 body inside and out with POR-15. I'm not concerned in the least about the paint lifting off the POR-15.

 

You are wasting your time if you don't take it apart and clean it out. Everyone I have talked to said after a couple years their paint blistered no matter what they used on it around the roof seam.

I can guarantee you for every spot of visible rust you see, there are probably 10-20 places in the seam and along the drip rail....

Do you have any pictures?