mkenny

This is a continuation of an earlier discussion, thanks for all who replied. I am converting a 70 cutlass supreme non a/c to a/c. I have found all the a/c parts from someone on this forum (thank you very much) and now need to know how to modify my original firewall to fit the a/c stuff. How is this best done? Some holes need to be modified and closed up and some new ones need to be created. What's the best way to do this?

dfire25

Here is a pic of what the PO of my car did to pass it off as a factory A/C car (not a very good job mind you). He didn't bother covering the large heater hole, he just cut for the A/C pass though. Also the interior box didn't quiet line up inside so the vacuum canister on the end of the box interfered with the gas pedal. Not fun when you punch it and the gas pedal stays down! So make sure everything lines up both inside and out.

If you wanted to do it on the cheep, I would just get a piece of sheet metal from the hardware store and cover the hole, then cut out what you need. Most of it would be covered anyway so you won't see it. If you wanted a more "factory" look, you could buy a new A/C firewall and cutout what you need. You would have to cut the existing firewall out and weld it the new section, but it would look more factory correct I guess. Just a lot more work.

dfire25

Here is how my firewall turned out. I wanted a smooth firewall because I was using a Vintage Air unit. All it is is a piece of duct work sheet metal and I bondoed the edges by the center to make it look smooth.

MDchanic

When I put A/C in my LS6 Chevelle in 1981, I just cut the hole in the same place it was on the donor car, patched the "extra" hole parts with aluminum siding, pop rivets, and house caulk, and found that the locations where the new hole had to be drilled were all "pre-dimpled" at the factory.

- Eric

1968_Post

If it would help you, my 68 442 factory a/c car is apart. I can take pics of the firewall without the evaporator case and then with the case mounted so you could judge placement. I also can take a few measurements on a couple of the mounting holes to get you started...

mkenny

thanks for the replies. I think what we're going to try to do is order the a/c firewall insulation pad precut with all the holes, line it up and cut what needs to be cut out of the existing firewall then patching up the rest with sheet metal, weld, grind, and paint as needed. Thanks again, and I will be in touch with those who have replied if I need more help. Can't wait to get this thing done.

69442murph

I have a piece of a/c firewall I would be willing to let you borrow, but I would want it back.
If interested, let me know...shipping both ways would be on you, but this way you would have an actual piece to use as a guide...
or I can provide pics....
thanks
tim

mkenny

to 69442murph,
I would be interested in the firewall piece if shipping would be reasonable. Let me know how to contact you directly,
Thanks, Mike K.