Good Evening all!  Has anyone installed a new evaporator?  I am in the process of rebuilding and restoring the AC and Heater systems and their installations.  Going with the original 1980 set up, couldn't swing a vintage air system at this time.  Question, if anyone has tackled this job, what the heck is the deal with the extra large gap all along the seam for the evaporator case where it bolts to the Blower Motor case?  The assembly manual calls out for sealant around these areas, but that's a heck of a lot of sealant. I don't recall how much was in there when i took it apart as that was quite some time ago.  You can see from the one picture what was on the inside when I pulled it apart...it was actually worse than the photo shows.  The other photos show the gap I am talking about.  The edge of the evaporator case has molded stand offs where each bolt goes through.  These bumps are what causes the two halves to have such a gap. As these parts are original, the gap seems like a forgone conclusion.  I'm hoping someone has worked this, if so, what did you use to fill the void?  The manual calls out Sealer-Black Pumpable and the assembly note says, bead must be .38 Dia min, measured perpendicular to flange.  There is a groove in the case half that will take strip caulk, but to build up enough to close the gap seems kinda crazy...or bad engineering. 

Any guidance would be appreciated. 

The photos are a little hard to understand, but...I can tell you these cars were NEVER sealed properly, as far as the HVAC systems go. A photo from a different angle(viewing the bolt side down) might help. 

You could use a 1/4"-5/16" urethane rope seal in the areas with a largest gaps, and sealant to make it all airtight. Just know this....the HVAC systems on these cars are nothing more than a series of leaks. Just too many variations from one car to the next to expect anything to fit properly. It sucks, but that's how they were built. 🙁

Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thanks Adam.  Yes, I see the photos are a bit odd in the orientation.  The gap should be vertical as that is the way it sits installed.  I will definitely figure out a seal method to keep this as tight as possible.  I'm not afraid to make some modifications to tweak the original designs.  I will make this system tighter than it originally was.  I just have to avoid sealing it up so that I can never get into it again :(  These cars definitely came off the line with parts being fitted every which way.  

While you have it apart and on the workbench, you might think about doing the C4 blower motor mod.  Just need to make a 3/4" spacer for the motor housing.  Some folks used a plastic cutting board of the correct thickness.

You get more air flow with the C4 Corvette blower fan.

Starting with the 4th post in this thread talks about it:

https://www.c3vr.com/vrforums/message_go.asp?MID=320520&Jump=1#321861

Thanks, I will do that for sure.  I had seen some stuff about that on different websites.  Question, is that adapting the C4 motor and the fan together for the C3, or is it just adapting the C4 fan to the C3 motor?  I have seen where the C4 fan is bigger and would provide more flow, but I hadn't see if the C4 motor also need to be used.  I have the whole firewall apart, so I have good access and I am updating and renewing everything.  Better to do it all now before it all gets put back together and becomes a pain to access. 

The whole C4 assembly.  Trying to remove a fan squirrel cage and put it on another fan might muck things up. 

Adam is familiar with this conversion and can tell me if I'm wrong.  😁

Great, I will take a look at that thread.  I also have just been looking at some youtube videos that dealt with this conversion.  I would definitely like to have more airflow.  It will also be nice to have clean air coming out, which after taking everything apart, I know how fouled up this system can get with debris.