Replace Heater Core: 1967 Special with AC

Discussion in 'The Big Chill' started by 12lives, Dec 11, 2019.

  1. 12lives

    12lives Engage! - Jean-Luc Picard

    I've read the manual and looked on line but I can't find all the studs for the heater box. To replace the heater core you have to pull the under dash box out which has 5 studs that pass through the firewall. But, I can't find the two upper nuts on the studs from the under dash box. [​IMG]
    Last edited: Jan 28, 2020
    mineseats9 likes this.
  2. 12lives

    12lives Engage! - Jean-Luc Picard

    I figured it out, so just for the record:
    Here is the back side of the HVAC blower box on the engine side of the firewall:
    Here is the heater box under the dash, the side facing the firewall:

    and a close up:


    The studs on the inside box extend through firewall and through the frame of the fan box on the engine side and are somewhat easy to see if you know where to look.
    Last edited: Jan 28, 2020
  3. 12lives

    12lives Engage! - Jean-Luc Picard

    There are three studs/nuts on the bottom of the heater core box inside the car under the dash. See the top pic above, bottom is to the left. Easy to see in the car, they are on the very bottom of the blower box on the engine side. The top of the box has two studs/nuts and two dowels. You can see them in the lower two pics above. The left one is under/behind the hood hinge on the passenger side. On the top pic its the hole at the bottom and in the bottom pic its at the left.

    The other top stud/nut is between the top heater hose and the rubber grommet on the front of the fan case. In the top pic its the rusty slot in the center of the picture. On the car you have to find the top heater hose and its up and to the right about 2 inches. Look behind the passenger side valve cover.
    You can see the top hose connection to the left and below it. The vacuum canister and the grommet are above it.
    Last edited: Jan 1, 2020
  4. jonmil

    jonmil Well-Known Member

    Good info. I also have A/C on mine
  5. 12lives

    12lives Engage! - Jean-Luc Picard

    Merry Christmas! I'll post more as I get into it...
  6. 12lives

    12lives Engage! - Jean-Luc Picard

    I got the 5 nuts off the engine side. Here is some info on those:
    I used a gear type ratchet wrench to reach the nuts behind the hinge and the inner fender:
    I did have to use a heat gun the soften and remove the black goop they used as a sealer where it covered the nuts. I did not have to cut any holes or remove any parts to get to the lower left one behind the inner fender. It was tight but very do-able. We'll see how it goes getting it back on!
    The other three nuts came off with a socket and some extensions.
    You have to remove the kick panel on the passenger side to get to the retainer and seal assem. that holds the right side of the box to the AC shroud under the dash. Of note is a screw on the door jam that is not on the later cars:
    Last edited: Jan 1, 2020
  7. Dr. Roger

    Dr. Roger Stock enthusiast

    Ratchet wrenches are the greatest invention in our lifetime :)
  8. 12lives

    12lives Engage! - Jean-Luc Picard

    Oops - did I say 5 nuts? Someone on the board advised me that some factories put nuts on the AC/heater assembly (the part under the dash) studs to hold it in place while they did the Plenum Blower Air Door Assembly later on the line. And lucky me I have those extra nuts NOT mentioned anywhere in the manual/parts book. Follow the manual section 13-31. I got the retainer and seal assembly off:
    You do not need to remove the small 1/4 screws around the perimeter on the shroud side duct. Just the two 7/16ths and the 1/4 facing you in the center. The retainer is in 2 pieces and the part you see slid over comes right off. That releases the side under the kick panel. The manual says work the assembly from the cowl. Yes, pull and tug because its glued to the car with all the black goop. BUT, if it won't come loose check for the extra nuts:
    That's one on the stud next to the upper heater core nipple. And:
    IMG_0853.JPG that's the 2nd one on the bottom middle stud. You have to take the blower assembly loose by removing the screws across the top and prying it up enough to get a wrench in behind the flange, as shown. Again, the gear wrenches were a life saver.

    With the studs finally free the rest is like the manual says. Once the box is out you're not done. You have to split the box to get the core out because the retaining screws are inside. Boy, the later cars are easy compared to this!
    IMG_0854.JPG There are 4 screws holding the retaining brackets. Do NOT mix them up.
    Two on the left and two on the right. Of course they may be buried under the dreaded black goop. The factory sealed everything with that stuff.
    I posted a review of the Summit core I am using here:
    Last edited: Jan 28, 2020
  9. 12lives

    12lives Engage! - Jean-Luc Picard

    After disassembly, clean up, paint any bare spots, and preserve the bare metal. I just used Dawn and a long soft bristle brush to clean them up. Rinse good with hot water.

    I used anti-seize on the defrost door slide:
  10. 12lives

    12lives Engage! - Jean-Luc Picard

    When you install the core put the band in first. Leave the screws loose:

    Then the core and bracket:
  11. 12lives

    12lives Engage! - Jean-Luc Picard

    Assemble the fiberglass door assembly to the core side. There are 13 screws:

    I had to repair a few spots on the firewall mat that came off with the heater box. I painted the inside of the blower box from the inside of the car through the firewall as there was some surface rust. All ready to reinstall.
  12. 12lives

    12lives Engage! - Jean-Luc Picard

    Finally got it all back together. One issue was the upper connection. I used the non-AC heater core as it has a straight upper inlet instead of the AC core that has an inlet that angles toward the engine. My long term plans are to go with a BBB and I wanted the extra clearance, buuuttttt... The firewall hole is wide to make room for the angle and the straight inlet is too far to the right:
    Heater upper inlet.jpg

    This required clearancing the hole so the connector was not rubbing. After that everything with back together as in the manual. I found a nice 90 degree hose for the lower connector so it goes straight to the water valve with no kinks or bends:
    Part Number Gates 28467 Heater Hose.
    The black goop had me stumped until I found this:
    Rutland Seal it Right 800-Degree Latex. It matches nice. We will see how it holds up.

    That's it. Hopefully this helps.
    Last edited: Jan 28, 2020
  13. stagedgs

    stagedgs 1967 GS400

    Awesome write-up, Bill.
    I tried to replace my heater core a while ago and I could not get the heater box to let go of the FOD. I thought that the butyl had set up as it is over 50years old and was being difficult. I was planning on removing the dash (which I need to do anyways to replace the original wiring and restore the dash itself), in the hopes I would then have access to the bottom and sides of the heater box and then slide a putty knife between the FOD and the heater box to get the butyl to submit. Now, it may be the hidden nut that I was fighting. I was SO afraid that I was going to bust the flange on the heater box, and I'm sure I would not be able to find a replacement for the busted heater box.

    Also, what did you use to replace shroud side duct to heater box seal? The nasty, black, gooey, shi-stuff?
  14. 12lives

    12lives Engage! - Jean-Luc Picard

    I used the Rutland Seal it Right 800-Degree Latex. It has held up well. I did NOT clean off all the old stuff so I only had to fill in the areas where the original goop broke off.
    Also, on mine there were two extra hidden nuts, see above.
  15. stagedgs

    stagedgs 1967 GS400

    Thanks, Bill. You gave me hope with respect to getting my heater box off in one piece.
    I'll get to it this year, I have to. My car's been sitting too long. Work's been draining. I get home from work and I'm done for the day. Don't get old. :)

    Thanks again,
  16. 12lives

    12lives Engage! - Jean-Luc Picard

    Too late Mike - I am old! :rolleyes:
  17. stagedgs

    stagedgs 1967 GS400

    I blame my wife. She made me old, I wasn’t old when I met her.
    12lives likes this.

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