heater core assembly ???

[Tinkerr]

Does anybody know what the substance that the heater core rests in to keep it from chafing against the heater box assembly is? Mine is hard, black, and brittle. I'd use caulk, but I'm not sure it has the suspension properties necessary to avoid the chafing. I've also considered the black tar ribbon used to install windshields. Any idea's?

[rich69rs]

When I replaced my original core last year, I used a new seal kit, made sure the clip on the RH side of the core was properly engaged, and used caulk to seal up the gap between the front of the core box and the firewall.

Pic 1 shows the new square seal on the door.
Pic 2 shows ths gasket seal that goes on between the heater box and the core.
Pic 3 shows the new core installed with the clip installed.  The clip slips over the box and has fingerst that push the core against the back seal.  There is also a seal that goes around the inlet and outlet pipes.  All of these seals are in the seal kits available throught the aftermarket.
Pic 4 shows the caulk going in between the heater box and the firewall.  About 60% finished when this picture was taken.  This was something that I added - I didn't see any sign of anything in this gap originally.

First pic.

[rich69rs]

Second pic

[rich69rs]

Third pic

[rich69rs]

Fourth Pic

[rich69rs]

Tinkerr -

Was the heater core that you removed original? 
 
When I did the front end mechanicals 2 yrs ago, and due to great timing with the CRG report on cooling systems, I realized that the radiator was the original., Jan 69 date coded, base SB V8, non-AC, 2 row radiator  Then I pulled the heater core and I realized that it too was original to the car.  

Finding the original radiator still in the car was interesting enough.  Finding the original heater core was interesting in its own right. 

Pics below are the heater core that came out of my '69:  manufactured by Harrison and clearly date coded 69A (Jan 1969).  Build on my car is 01C.

[rich69rs]

Stampings on the tank on the blind end.

[Tinkerr]

Rich,

I believe the core is original, it's dated 67 M which would be Dec 67 build date is 04A of 68. It looks like the sealer/caulk I'm referring to is just visible at the top where the gray meets the black area in pic# 2, looks like a bead of caulk. This was on the top and bottom of the heater(very hard and brittle) box and the core sat against it I believe so it didn't chafe metal to metal.  I was of the impression the firewall pad went between the heater box and the firewall and thats what sealed the area you place the caulk in pic# 4 ?

[JohnZ]

  I was of the impression the firewall pad went between the heater box and the firewall and thats what sealed the area you place the caulk in pic# 4 ?

That's correct - the dash mat went on first, and served as the seal between the front of the heater box and the inside of the firewall.

[rich69rs]

Nice - Harrison obviously built some pretty good radiators and heater cores for them to last this long.

When I changed mine, I removed the heater core from the firewall side.  Didn't remove the heater box from under the dash.  Once the blower motor / outer cover was removed from the firewall, the heater core was easily accesible.  However, when I did take it apart, the only seals on the heater core were the seal on the inlet / outlet pipe connections and what was left of the seal on the door.  There was no obvious seal behind or in front of the core itself.   From what you and John have pointed out, I got the seal on the wrong side of the core, but it sure made it fit nice and tight and is well cushioned.  Only problem that created was that I had to manually seal up the gap with caulk. 

One benefit of putting the pad on the dash side of the heater core was the alignment of the inlet / outlet pipes.  With the pad on the dash side of the core they exited through the firewall properly.  Without the pad on the dash side of the core, they didn't want to line up correctly with the cutouts in the outer cover - one of those repro issues - at least in my case.