Heater Core Removal/Installation - '68-'72 NON Air Conditioning A-Body

Discussion in 'The Big Chill' started by Brett Slater, Dec 30, 2022.

  1. Brett Slater

    Brett Slater Super Moderator Staff Member

    After replying to someone on (oddly) a '70 Chevelle SS Facebook page earlier today, I felt it was time to create a thread devoted to removing and installing the heater core in your 1968-1972 NON air Skylark or GS.

    First things first: it's important to try as hard as possible to source a radiator repair shop local to you. The factory fitment & function of the Harrison is second to none. I understand radiator repair shops have become a lost craft but if you have one local, use it and insist on the high efficiency cores from Maine Auto Radiator in Lewiston, ME. As with everything, the prices have gone up, so expect to pay in the $250 ish range or even a little more. That's how much the last one I had done cost earlier this year.

    My radiator guy - who recently sold his shop but will (hopefully) be doing radiator work on the side this spring - used these cores on close to a dozen OEM heater cores and radiators for me over the last few years and those that have been installed have worked flawlessly. You can roll the dice with a made in Mexico/China reproduction core - and it may never fail - but it's not a job you'll want to do more than once, if you can avoid it and the repros are prone to lousy tube fitment and leaks over time.

    Once you've figured out which direction you'll go in terms of a new core, it's time to get down to business on this two person job.

    After you've drained the coolant from the system, you're going to want to make as much room as possible in that front passenger's side area. I ended up pulling the seat out. Taking into account how much time you're going to spend on your back, I recommend removing it. The dash pad, glove box liner and (eventually) the radio came out as well. In retrospect, I'm glad I made as much room as I did.


    After you've made enough room to be comfortably uncomfortable, it's time to tackle the 5 speed nuts on the firewall side of the heater box.

    The long standing myth is that the inner fender needs to be removed or a hole drilled in the vicinity of that annoying "hidden" speed nut that sits behind the top of it. In fact, I recall reading in one of the factory manuals where it was recommended to drill a small hole as I've previously mentioned. I'm not interested in drilling any holes in my car but you may be - who knows? My resolution was this rachet/wrench and patience.


    It will come out, you just have to take your time. The other 4 speed nuts are easily accessible. There are also 5 pieces of round foam called heater stud seals that (I think) I got from Ames Pontiac but didn't use because I didn't remove the heater box on the firewall side. It's best to have all your ducks in a row when doing this and that's what I was trying to do.

    Now that the heater box is loose , the heater hoses are disconnected, the heat duct under the dash is removed and the heater cables have been carefully removed from the heater box, you and your helper are ready to pull the entire assembly into the passenger side footwell. Non air cars will have that pesky blue tab that wraps around the cable and affixes to the top of the heater box. It invariably always breaks, more so because it's the one that is used most often, that opens and closes the door in the heater box.


    The red one above is typically fine and the fix for the blue one that will break is a cable clamp like this:

    20220326_211613.jpg 20220327_114914.jpg

    Once the box is out, it's time to clean 50 plus years of dried up goop and cracked foam on both sides of the actuator door.

    After you've scraped everything off, you'll need some 3M strip caulking for the section the new core sits in inside the heater box. You're also going to need a sheet of 1/4 foam for the little door. The bad news is: you're going to need to figure out a way to get a piece of that foam on the backside of said door. You can leave it off but be prepared to hear a "thud" each time you move that cable to shut the door. If you have small hands, you'll struggle but it'll be doable. If not, you may want to ask the Google machine how to become a contortionist.

    20190807_201212.jpg 20190807_210537.jpg

    I used Weldwood contact cement brushed on both pieces of foam. You want to cut it just a bit bigger than the actual size of the door and remember, you only get maybe one or two stabs at affixing the foam to the backside of the door. Be patient.

    Once your new foam is glued back on and the caulking strip - which is very easy to manipulate - is sitting in the heater box, it's time to secure the new core in place.

    20190807_211256.jpg 20190807_212311.jpg

    And now you're ready to reverse everything I've just typed.

    You and your helper will now have the incredibly enjoyable task of maneuvering the cumbersome, refurbished box and shiny heater core tubes under the dash and through the firewall - with limited space to move around - while trying to make sure you don't bend said tubes. It really is fun for the whole family.

    Once the box is back in, you're going to hook the cables back up to the heater box. Hopefully all three of the aforementioned plastic tabs are still intact. If not, at least now you have a reference.

    That annoying speed nut goes back on with some dum dum on your fingers to start it onto the stud. Once you start it, you can use the wrench to snug it up to the firewall.

    3shields likes this.
  2. CJay

    CJay Supercar owner Staff Member

    Pretty sure you can remove that door
  3. Brett Slater

    Brett Slater Super Moderator Staff Member

    More power to whomever can.
  4. SteeveeDee

    SteeveeDee Orange Acres

    Wish I'd known the solution for that one nut before I pulled the hood and fender off my '68...and then had to do it again a few years later because that ******* ***** cheap Chinese heater leaked. 35 years for OEM, 3 years for Chinesium. The brass one I bought is still in the Skylark I sold to Sebambam.
    Brett Slater likes this.
  5. CJay

    CJay Supercar owner Staff Member

    I recall removing it when I did the core in the aqusmist car. I believe there was alot of kroil, a Tonya harding (hammer) and a punch
    BadBrad, Dano and Brett Slater like this.
  6. Brett Slater

    Brett Slater Super Moderator Staff Member

    It's worth the money for the re-core of the Harrison to not have to go through the hell again in a couple years.
    Dano and SteeveeDee like this.
  7. BadBrad

    BadBrad Got 4-speed?

    I did the hole-drilling thing on my A/C equipped GSX back around 1987. Unbolted the wheelhouse from the fender two or three bolts up and then peeled the two halves apart with a wedge. I could then see the impossible bolt. I split my vision by using my nose as guide between the two sides of the wheel house; with both hands simultaneously on either side of the sheetmetal I made "virtual" contact via the split vision and marked where I would drill from the tire side. A 1.25 inch holesaw (still have it!) was employed to cut about 300-ish degrees of circle. I folded the flap back and got the bolt. When done I folded it shut where it could've been welded, but I just gooed it over to seal it. Current car that I've had since '93 had similar repair work prior to my ownership although not as ingenious; the hole is there but nobody thought to simply fold over a flap. I can push a rubber plug in that hole, but we never ride in the rain. In 2008 when I last had the drivetrain out I replaced the core.
    Brett Slater and Dano like this.
  8. Rich Skylark

    Rich Skylark Gold Level Contributor

    Has anyone else put together a a thread like this for heater core removal/installation on A bodies with a/c ? I’ve never done one on an air conditioned car and I’m pretty sure it is more “ labor intensive “Nice job on this thread .
  9. Brett Slater

    Brett Slater Super Moderator Staff Member

    Thank you.

    I don't recall seeing one and agree it's definitely a lot more work than I've posted.

    I guess you would have to remove as much of the air conditioning unit as you'd need to in order to start the process I've laid out in this thread.

    No matter who you slice it, it's an absolute suck job.
  10. Buicksky

    Buicksky Gold Level Contributor

    Brett thanks for sharing. Surprised it is possible without removing the outside box. Great to know.
    Brett Slater likes this.
  11. Brett Slater

    Brett Slater Super Moderator Staff Member

    You're welcome.

    It's very possible, as all the work is basically in the heater box under the dash.

    Trust me when I tell you that there's absolutely enough work for a person - or two - that removing the firewall heater box isn't necessary. :D
  12. Dano

    Dano Platinum Level Contributor

    I remember doing one on my GF's no A/C '66 back in the day (on the street) and getting to one nut was the hard part but didn't actually pull the firewall box IIRC.

    A few years later working as a mechanic I had to do one on a Ford Van. Was kinda dreading it & amazed how quick/easy it was.
    Brett Slater likes this.

Share This Page