You have to start somewhere. Floors and frame rails have to be replaced. Feedback from the Z forums says to do the frame rails first.
You have choices on frame rails. You can get exact replacements for the factory frame rails. You can get frame rails that fit over the factory rails. Or you can get full length frame rails – these extend further back than the factory frame rails and tie into the rear subframe.
Extended frame rails stiffen up the entire body and chassis – a useful upgrade. After a fair amount of research I selected a set of Apex Engineered full length frame rails. These frame rails are made from 16ga steel, almost twice as thick as the 20ga factory frame rails. They are also deeper than the factory frame fails. All in all they are a significant upgrade in strength and stiffness for this critical structural member.
With the frame rails in hand the first step is to mask the areas that will be welded and then coat the rest with two coats of epoxy primer. After the epoxy primer dries remove the masking and coat the rest with weld through primer. Unlike Datsun, I want to do everything I can to prevent future corrosion problems!
Starting with the drivers side, the next step is to remove the original frame rail. It turns out that the drivers frame rail had already been “replaced” with a frame rail that fit over the factory frame rail.
Notice the “chicken poop” welds “securing” the replacement frame rail to the structure of the car. At least these were easy to cut off…
Going back, there were no “chicken poop” welds. Because there were no welds. The only thing holding the replacement frame rail to the car was undercoating. I will decline to make any further comment…
With the replacement frame rail off you could see the remnants of the factory frame rail. This was at least welded in place. Drill out the factory spot welds and pull the old frame rail off.
I don’t think that was adding much strength to the car…
Here you can see the floor where the factory frame rail was removed. It is badly rusted, an indication of the poor corrosion control common to that era.
With the old frame rail off it was time to test fit the new frame rail.