Car Frame Rail Replacement

Applied Vehicle(s): All Nissan/Infiniti vehicles Difficulty Rating: Estimated Labor Time: 5 hours Written By: gmac708 Estimated Total Cost: $95.00 Find related tutorials and information on your vehicle in NICOclub’s Nissan Forums & Infiniti Forums

I recently replace the floors in my 1970 240Z. I used the Zedd findings floor panels and the Baddog parts frame rails. Both are quality manufacturers but they do not supply the finished product. It’s more like they supply the raw materials, and you supply the “fab” skills.
I hope posting these pictures and comments might answer your questions and help you get a better idea of what needs to be done (and what the heck, it can’t hurt to have a few more pictures) . I am lucky enough to start out with a pretty solid frame. I think you could easily add extra length and bracing to the Bad Dog frames, they are pretty heavy duty.

I had just completed the passenger side and we are picking up where I moved over to the drivers side.

As you can see, the factory frame rails extend back only part way back.

They do not extend all the way back to the rear suspension support frame.

I chose to replace the factory rails with the beefier and longer aftermarket ones because they are commonly used in high HP V8 swapped Z’s, and Bad Dog seems to be the product of choice. They will end up connecting the front and back frame structure together.
The BD frames fit like a glove over the factory rails. I chose to not replace the original, but just remove the damaged areas and cover with only the BD rails.

Up front you can see the damaged area.

This sort of has an “S” bend and is pushed up in back. Not all that flat.

Looking from below, You can see that the frame tapers as well. I chose to leave as much of the original frame alone and only removed the bottom, damaged areas, and what was necessary to keep it flat.

Cut just aft of the floor seam.

Leaving this.

Now… to make the bottom flat.

Support and hold new frame in place.

Here you can see where the frame tapers.

New frame extends to second mark.

I chose to remove the extra material.

Everything fitting well.

Now for the Back.

This took a lot of extra time to get to fit right.

Need to trim the length to match the front rail.

Make sure you measure everything over and over. Keep the rails parallel and flat. Take your time.

When everything looks perfect, It’s time to start welding! Start off by tacking around, using a criss-cross pattern. Do not stay in one place. Move around

It turned out great and I was very pleased with the floors and rails. I hope this helps to answer some of your questions and helps to motivate you to attempt this repair.