​​​​​​​​​​​Fresh Air Inlet Door 

With a heat gun at 550 and a thin putty knife, I removed the blower motor mounting panel shown at right.  Though the bracket didn't slide in as I thought it would, having this panel out made the installation easier by allowing access to the space behind.

Next I set the heat gun on low and cleaned out the yellow sealant with a putty knife.  Be sure to get all sealant out of the bracket mount point located behind the firewall and just above the kick panel vent hole.

To remove the Astro vent inlet, I set the heat gun to 550 and used the putty knife.  Obstructions prevented me from getting the putty knife completely around the inlet.  To finish, I held the heat gun as near as possible to remaining area.  After about two minutes, I tapped the vent from underneath with a 4 lb dead blow hammer and it popped out.  The inlet adhesive lip had softened and broke off.

I fit checked the inlet bracket, and that's when things begin going sideways on me.  The first attempt failed because the bracket wedged against the kick panel vent port.  I got the brilliant idea that removing some of the port I would solve the problem.  I removed a section using a dremel cutting wheel, but the bracket still wouldn't fit.  After removing more material it still wouldn't fit, and I erroneously concluded that the vent port needed to be removed.  I won't go into the gruesome details here, but I posted a walk through for the repair of that unfortunate piece of hardware. (vent port repair)

After all that, the bracket still wouldn't go into place.  That's when I realized it was about 1.5" too long.  So I cut the bracket as shown.  The bracket "box" is too large.  The short, vertical side contacts the back of the opening before the front clears the firewall.  Any cuts to this bracket must either remove the short vertical side and part of the bottom, or shorten the length of the box.  I chose to shorten the box with two vertical cuts.  In retrospect, I think it would've been easier to cut the firewall.

I fashioned a jig from 1/2" steel flat and used M6 machine screws to secure it.  After grooving a piece, I bent it to follow the bracket's contour.  I drilled the holes and assembled it using lock washers so the screws would stay finger tight against the nuts.  In the picture, there is a small gap between the bracket halves.  This represents material removed by the cutting wheel.  It's important the bracket maintain its original lines and dimensions so the fresh air flap seals properly.


I placed the pieces behind the firewall and assembled them for a fit check.  You can see the hardware, and I was concerned this would interfere with making a good bond and with fresh air inlet operation, so I decided to remove the hardware and fill in the holes with a structural putty.

Filling the gaps is much easier said than done.  I used aluminum tape to keep the putty from bonding to the car.  Be sure to tighten the nuts finger tight only because you won't get a tool on the backside of the screws.  I was careful and got really lucky to not get any putty on the threads.  Had I been smart instead, I would've covered the nuts with masking tape.

I made structural putty from epoxy (West 105 System), colloidal silica (also from West) and 1/32" milled fiberglass (from Fibreglast).  I mixed the silica and milled glass at 2:1 into the epoxy until it was the consistency of frosting and smeared it into the gaps with my finger.  After 24 hours, I removed the tape and hardware.  It's a tight fit, but if you take your time, it can be done.

​It's easier to seal the Astro vent hole before inserting the bracket, but I got so absorbed with getting the bracket in I forgot about it.  It's very straight forward and you can click through the series on the right to check it out.   I used aluminum tape for backing material (top L & R) and cut four squares from a piece of 4 oz fiberglass cloth, and abraded around the hole with 36 grit sandpaper.  I mixed a batch of epoxy.  So it wouldn't run, I added colloidal silica until it was a ketchup consistency.  I laid the squares in from smallest to largest.  You can see how the colloidal silica makes the epoxy mixture white after it dries.

I used Evercoat SMC panel adhesive to fix the bracket in place. It's stronger than needed, but what I had available.  I liberally applied it with a plastic putty knife and finger, trying to maintain a minimum 1/8" adhesive thickness.  It's a very messy job and the stuff gets everywhere because the space is so tight. I used a spring clip to hold the bracket in place while the adhesive set.

After curing, I used a mirror to inspect the bond. Some areas that needed more adhesive, particularly the gap between the fender and bracket, and the gap at the end of the bracket.  When finished, there was quite a bit of excess adhesive to remove.

I used a heat gun, flexible putty knife, razor, and exacto knife to remove the excess adhesive.  The bracket has pass through holes for attaching the flap, and it's important to ensure the mounting surfaces are clean or else the inlet flap will not seat properly, resulting in a poor seal.  Also ensure the contact area between the inlet flap and bracket is free of adhesive.  After a couple hours, I had cleaned the excess adhesive and smoothed / shaped what was left.

Using a dremel tool and small, spherical engraving bit, I made a weep hole (upper left) so water drains from the trough (visible in picture at lower right).  

I did a fit check, and the flap scraped against the firewall.  I was able to move it back some by loosening the mount plate hardware. Notice the slight notch at the top of the flap (upper right).  It was there when I bought it, but put there to help clear the panel adhesive seam contour.

Applying vacuum, I checked the seal around the bracket using a bright work light.  The fresh air flap is flimsy and able to conform a bit to the bracket edges.  It's a pretty good seal.

I used the SMC panel adhesive to put the kick panel port and blower mount panel back in place.  I cut a 1/8" thick plastic washer for spacers so the clamps would't squeeze out all the adhesive.

SUMMARY: I'd rate this job an 8 out of 10 the way I did it.  If I did this again, I'd remove the blower panel, clean out the old sealant, and remove the Astro vent inlet.  Then I'd remove enough firewall to the left of the blower housing mount to insert the fresh air inlet bracket without cutting it.  I believe this makes applying the adhesive easier.  I also think repairing the cut firewall is easier than the jig rig I came up with.

​This work is a necessary part of the Engine Bay and Firewall project, which is my goal for summer 2015.  The remainder of this project is deferred until later, except for the Evaporator / Heater Box rebuild detailed in a different walk through.

Kick Panel Door

In addition to the cowl flap installation, I also needed to rebuild the flap behind the kick panel.  If you have the astro ventilation system there are two.  For a/c equipped cars, there is only one on the passenger side to facilitate cabin air circulation through the evaporator box.  In this configuration, a vacuum actuator acts in conjunction with the cowl flap.  On max a/c the kick panel flap opens and the cowl flap closes.  On any other setting it's vice versa.  The rebuild kits and vacuum actuators are available from the vendors, but the brackets and levers are not.  At right is the one I purchased off e-bay for the brackets.

These doors are held together with semi-tubular rivets.  I used a dremel and grinding head to remove the curled lip of the rivet and a punch to knock it through the back.  There are seven rivets to remove.  Once they are out, the two halves peel apart and the foam dam is between them.  I sandblasted everything and powder coated the to flap halves.  I used satin clear on the bare metal pieces. 

To put the halves together, I pushed the rivet through the flap and used masking tape to hold it in place.  Then I put the new foam dam  in place followed by the other flap half.  I used a small ball bearing to curl the semi-tubular rivet.  I learned about this on the forum, but did not have much luck with it.  The bearing had a tendency to slip, deforming only one side.  I ended up using a punch to finish curling some of the rivets, which resulted in some splits.  I think it will be fine for holding the halves together.

SUMMARY:  This was fairly straightforward.  I would give it a 4 or 5 out of 10 the way I did it.  I recommend getting a semi-tubular rivet tool and save yourself the headache of trying to curl these back with a bearing and / or punch.  With the proper tool, this would easily be a 3.

The title of this section should be "How NOT to Install a Factory Air Conditioning System".  At least that's how it's starting out, as you'll see below.  My car is one of a handful delivered without air conditioning.  Seventy nine is the last year it was optional, and I don't know whether the original owner was interested in performance or just cheap, but the cabin gets miserable during the Ohio summers.  Here are some things I considered:

AFTERMARKET DIRECT FIT KITS:  Direct fit kits like those offered by Vintage Air are attractive, but only retrofit up to 1976.  From 1977 on, the climate control panel and layout is completely different and earlier years cannot be used without completely changing the interior look.  These kits are electrically controlled and modifying them to work with a stock vacuum climate control panel doesn't seem feasible.  There are generic electric climate control panels available that may be adaptable, but they would look out of place and get away from my goal of maintaining the stock interior look and feel.

UNIVERSAL A/C KITS:  I checked out some all-purpose vacuum controlled systems, but they required placement under the dashboard, an area limited in foot room in the first place.  Some posts indicated interior modifications, such as cutting holes in the glove box, were required for these systems.  Finally, none of them seemed to make provisions for heat.  Granted, I rarely use the heat, but it can be nice cruising with the T-tops off on a brisk fall evening with the heat running.

STOCK RETROFIT:  The only remaining solution I was happy with was installing the factory a/c, with some upgrades to improve performance.  I believed that with the car was off the frame, it would be a fairly simple undertaking.  I didn't know what I was getting into at the time...

First is parts availability.  I scoured the internet and found no after market vendor for the fresh air inlet bracket, either half of the evaporator box, the linkage and bracket for the passenger kick panel door, the interior heater box, the heater / defroster duct assembly, the center duct, or the defrost duct.  I acquired these from e-Bay vendors / members, and forum members.  These are used and some require repair.

My research indicated the fresh air inlet bracket would be the hardest part of the retrofit.  For those that don't know, it's on the passenger side, tucked way back behind the cowl screen.  The fresh air inlet is not required to equip the car with a/c, but it is necessary for the "Max AC" option to work.  When "Max AC" is selected, the fresh air inlet flap closes and the kick panel door opens, circulating cabin air through the evaporator box.  The posts I read involved inserting the bracket from the cowl.  Since I have the car on a body dolly, I plan to remove the blower motor housing mount panel from the firewall and insert the bracket that way.  As you will see, it did not go as smoothly as I thought.  I'll briefly summarize what I would've done differently so others can learn from my experience.

​Modifications:  Four

  • Enlarge hole in firewall
  • Install fresh air inlet support bracket and hardware (e-Bay)
  • Install kick panel port bracket and vacuum actuator (e-Bay)
  • Cover driver's side kick panel port
  • Plug Astro Vent​ holes

Upgrades:  Four

  • Install blower cage from C4 (AC Delco 15-8418)
  • Install Sanden compressor
  • ​Install parallel flow condenser
  • Cover blower motor and evaporator housings with thermal paint (Hy-Tech Metal Shield #1267)​​​

Air Conditioning

Progress  so Far