Firewall Replacement (Conversion to Factory Air Con) and Rust Prevention, part 1

Wow it's been awhile and this car needs to be finished. Now that the unexpected '68 XL is more or less a reliable daily driver I can return to work on this.

Just a quick refresher, these are the pieces that need to go onto this body for factory air con.

Eww, there's rust problems lurking everywhere.

I was hesitant awhile back cutting this much out, but I soon realized my body jig holds the body firmly into place. When the body jig is on flat level floor the mountings are +/- 1/16" tolerance. I could probably cut much more out without fear.

Just removing it carefully took some time.

Cleaned up some of the rust, there were still spots of bare steel from the factory that was never even primed. I split the top seam where I could to remove any heavy rust trapped in between.

A healthy coating of weld through primer was then used.

Since the top seam will contain three pieces, I went ahead and lined up the existing two and resistance spot welded them together so it's one less thing to fight against installing the main firewall section.

I did a rough fit and more accurate cutting of the body to make a space for the long butt weld needed.

Prepped the backside of the main firewall section.

The tedious part of firmly securing the main section of firewall to be welded back in.

Firewall Replacement (Conversion to Factory Air Con) and Rust Prevention, part 2

Many hours later. It's really tedious butt stitch welding 18 gauge without it warping.

Now all the welds, at least on the engine bay side need to be dressed off.

More countless hours.

I only had to dress off the lower right side of the welding as the interior air con plenum went up against the weld. The rest of it can stay as once it's assembled no one will see it. Plus in just this one piece I have 12 hours in it, I'm kind of over it and need to move on.

In case anyone is wondering what tools I used to pull this off, here they are. The flat shiny wheel on the angle grinder is a shrinking disk. Even though I tried my best to fixture this section in tightly before welded there was a small section above the smaller second hole from the left that oil canned. The shrinking wheel took that right out and the entire sheet is flat and true. The rest are self explanatory. I will say this, that miniature belt sander is worth its weight in gold.

Next will be to install the left front piece then I can go into both side cowl openings and start rustproofing before I put the side cowls back on.

Firewall Replacement (Conversion to Factory Air Con) and Rust Prevention, part 3

The next piece of the factory air con firewall is the side front panel. The hole is substantially larger for the heater core (factory A/C) than a heat only car. This is the dry fit up to make sure all the panels play nicely together and adjust any metal as necessary.

I want to weld that front panel in with the side cowl piece fitted as it will ensure it will fit later on when its turn comes.

It's especially important to get the front panel mated to the lower front panel properly otherwise the side cowl will not fit later on and that'll be a pretty poor show.

Both the existing firewall and the new piece are cleaned and primed with weld through primer on both sides.

Welded and smoothed out.

I grabbed one of the heater core plenums to double check the holes line up between the two sheets of metal forming the face of the firewall since this plenum extends over both of them.

The holes line up just fine with the plenum on both newly grafted in firewall pieces. Now I can start to treat the seams inside the cowl area for rust prevention.

More to come.

Cheers