Started with a good '72 Chevelle frame. Had it put on a frame rack and checked to “squarness” and frame sag. Once the frame was good, I added a slew of braces and structural improvements.
The first major addition was the boxed frame rails that I cut off a junk yard convertible frame that was messed up in the front and rear. I plasma cut them off, ground off any welds, positioned it on my frame and welded it in place. Of course this means that I will now need a convertible or el Camino cross member. I will show that later.
I left the center bracket that was welded to the original frame in place for additional support. Noted in next picture with *. This bracket would not be there on a convertible frame.
Starting from the front to back, I welded a gusset to the lower control arm perch connecting it to the engine cross member and to the frame. This gives additional stability. These brackets actually came from a mid-90’s Caprice Police car.
Any rusted body mounts were welded with washers to repair the holes.
I welded a filler piece in the factory tie down hole in the frame because that is often the start of frame cracks.
Welded in braces to support the rear lower control arm forward mounts.
Welded in mounts with ½”-13, 4” apart, tapped holes for later installing a roll cage and tubing that goes back to the rear bumper through the trunk. 70-72 Chevelle’s rear bumpers were bolted to the rear of the body not directly to the frame. These bars will help support the rear bumper directly to the frame.
Welded in gussets to support the rear upper control arm mounts and the rear cross member bumper bracket.
Lastly, for welding to the frame is boxing in all of the c-channel frame from the rear back. I used frame sections from other damaged frames and some flat plate to box being sure to not interfere with the fuel tank filler neck in the rear cross brace. One last thing to mention, drill out the drain holes from ¼” to ½” located on the bottom side of each front frame rail near where the front sway bar mounts. This way water can get out better. Also. Not on this frame, but on a different one I did, I welded in a plate with 2 tapped holes to beef-up the sway bar mounts, but the mounts on this frame looked pretty good.
Then, I took the frame to have it acid dipped and hot galvanize dipped.
I got it back, primed and painted it, then ran a tap through all the threaded holes to clean out the paint and excess zinc.
I used a cross member from a 71 convertible skylark. It is one piece of thick steel versus a tubular piece with a mount welded to it.
I chose this because it can’t rust on the inside like a tube. I had this galvanized as well, then primed and painted. When ready to mount in frame Torque bolts to 35 lb-ft.
I wanted to mount the battery in the trunk for two reasons, weight distribution, but more importantly, since I am putting a turbo LSX in the car I wanted more room under the hood for the turbo plumbing. So next, I ran a cable from front to back for relocating the battery to the trunk. I had to cut a hole to make a passage for the cable through one of the internal walls in the frame, otherwise it pushed right through the frame. I am not sure if a factory boxed frame (convertible) has this or not. Remember, this was a coupe frame that I boxed from a donor convertible frame. To gain access to the member inside the frame, I had to first cut a hole from the top, and then I could cut the steel membrane the needed amount to clear the cable through. Wish I had done this before galvanizing the frame.
*This was important to do before putting the front suspension on because it would limit my access to position the cable through the front.
I will finish both ends after the body is put on the frame.
Motor to Frame Mounts:
It is also important to install these before the front suspension because you need to access the hardware through the holes under where the lower control arm is bolted in.
Torque bolts to 35 lb-ft.
There is a left and right mount, the right one has the oval hole for the motor mount bolt and should have a “L” or “R” stamped on them.
Also be sure not to use frame mounts from a 307 car, they are wider and taller. 307 mounts won’t work with 350 and up also they might cause issues with an LS conversion.