A/C Firewall Template

[coop34]

Does anyone have a template or the dimensions of the a/c holes in the firewall? I'm converting my non a/c cab to a/c and need these dimensions to make the cuts to the firewall. Thanks!

[BIG ORANGE]

I saw a thread on here the other day where a guy did just waht your talking about but I remember the title of the thread, try reading through a few pages ahead and I'll see if I can located it also.

[mrein3]

That was me.
http://67-72chevytrucks.com/vboard/s...d.php?t=407052
Scroll down to post #11.

The firewall is easy. You simply take off your non AC heater core box/outside firewall setup. There is a dimple just above the one hole in your firewall. I purchased a conduit round hole cutter for a few bucks at the used tool store near work and made a nice round hole there.

With the two holes now in your firewall, make a paper template of those two holes and the hole in the firewall you're going to modify.

Then take your "new" AC outside firewall box and make another template on paper from it.

Line up the two holes on your two templates and trace out the area you need to make.

Cut that out of the paper.

Transfer that to metal.

Weld that in place.

Cut out proper AC firewall hole using your paper template from AC box.

Paint.

Done.

You don't need body work quality welds, etc here because everything will be covered when you are done.

[mrein3]

Couple more pictures. The first one is the paper template I made after lining up the two templates I made from the parts I had.

The second one is the hunk of metal I ended up welding in.

[coop34]

Thanks mrein. That will help alot! This may be a stupid question, but does the firewall really need to be modified? Would the a/c work fine if you didn't make any mods other than drilling holes for mounting?

[mrein3]

Originally Posted by coop34

Thanks mrein. That will help alot! This may be a stupid question, but does the firewall really need to be modified? Would the a/c work fine if you didn't make any mods other than drilling holes for mounting?

Good question. I'll bring this back TTT because I'm sure somebody tried it. If it would work I'm guessing that you would have reduced air flow through that hole.

For sure you'd have to punch that new hole for the heater core to stick out through the firewall. And I would spend the few bucks to get a hole punch because that hole will be obvious with the hood up. Don't hack it out with a cheap drill bit. Plus you need that hole to line up your templates to make the "J" you need to weld in.

You'll also need to punch a hole in the core support for the hard lines from the receiver/dryer and condenser. And unfortunately it is a different (larger) size than what you need in the firewall. But fortunately, like the firewall, the factory dimpled the core support where you want your hole punch centered.

I don't recall drilling any extra mounting holes. Just the modified HVAC hole, the core support hole, and the extra hole for the heater core.

[coop34]

I ended up cutting it by sight using the pics that mrein posted. I think I may be able to get away with not welding the J shape into the hole since it looks like that hole will be covered by the a/c and heater core boxes. I'll probably just add some weather stripping to the heater core box so that air cannot travel across. I'll let you know how it turns out.