'72 Underhood Mods

The Heater Box Conversion:
I needed to tackle the A/C-heater box situation. As you can see in the upper left corner of this bad picture, the factory air conditioning stuff is bulky and ugly.

The air didn't work when I bought the car and I didn't want it anyway so off it came just about as soon as I got the car home. But removing it left a large hole in the firewall and it left me with no heat and no defrosting system.

I went to a junkyard and picked up a Nova non-A/C heater box to put on my Nova's firewall to make everything wonderful again, but no such luck. The hole in the A/C Novas is taller and narrower than the hole in non-A/C Novas (short and wide). Also the heater hoses are in different places - with A/C the core outlets are under the hood hinge, without A/C the outlets are over above the passenger's side valve cover.

So I made my own.

I took a factory non-A/C box, cut off everthing to the right of the blower motor area and fabricated a housing to fit the A/C firewall.

Then I cut a hole for the upper heater core outlet to pass through and bolted it onto my car.

Nothin' to it. Actually it took many hours of measuring, cutting, bending, welding, grinding, and finishing to make it work but it was worth it. It looks and works MUCH better than a big hole in the firewall!

If you want more information, contact me. I did this myself about 20 years ago, but there are companies that sell similar items now, which is way easier!

Firewall Recessed Panel:
I've always had an HEI distributor in my Nova and clearance at the firewall was always tight, especially with an Accel SuperCoil. I decided to recess a portion of the firewall to gain some room around the distributor and clean up the rest of the firewall while I was in there.

There were a great many holes in it that weren't necessary so I marked the location of the distributor on the firewall, pulled the engine and then I started cutting. It was a little scary since I really didn't know what was back there, but it worked out fine. Here's the firewall after removing a bunch of unnecessary A/C wiring and cutting the hole.

This is after welding all the small holes shut, tack-welding a larger hole shut, and welding and trimming the recessed panel.


Further progress with the welder...

And the metalwork is basically done...

Now it's time to smooth it some...

I removed all the unnecessary wiring for the factory A/C that I had removed, cleaned up the rest of the wiring as well as I could and wrapped it all in that black split wire loom stuff. It really made a difference. Loose wires look sloppy! Even if I only had one wire running somewhere I put a piece of small-diameter loom on it to be consistent. I also ran my spark plug wires UNDER the headers to clean things up further.

And here is a close-up of the finished product.

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© 2020 Bruce Johnson and Craig Watson