C3 Heater Core Replacement on AC Car

[Robert S.]

I am replacing the heater core on my 74 (with AC). I got the heater box assembly out and the heater core removed from the box yesterday. With all the bolts and vacuum lines removed and the unit hanging from the top center stud, I found the final step of getting the heater box assembly out of the car somewhat difficult and found after removal that I had damaged the ends of the heater core tubes. No big deal as the heater core is being replaced but clearly the tubes on the new core cannot be damaged upon reassembly. I followed detailed steps I found in the archives for the disassembly steps which were great and had no issues or surprises during disassembly other than the tube damage. I know the tube ends were ok prior to the removal of the heater box assembly.

Question: Is there something that I should have removed from underneath the car to give the tubes more clearance as I removed the heater box assembly? Anyone have any hints on what to do or not to do upon reassembly?

[John M.]

Re: C3 Heater Core Replacement on AC Car

I replaced the heater core on my '74 ac car a few months ago. There was really no issues. There is a piece of foam around the lower section of the tubes on the engine side. It was not there on my car, i removed the bolts and one nut and rotated the assembly up and then down and it came out. When I installed it, just rotated the assembly up after making sure the tubes were in the firewall section and bolted in place. Then inserted the seal for the core tubes after it was bolted in.

[Robert S.]

Re: C3 Heater Core Replacement on AC Car

John - Did you remove the dash pad (the one that holds the speakers)? I did not as the instructions I was using did not say to remove but this is the only other thing I can think to do to give me more room to position the parts during reassembly

[Jim T.]

Re: C3 Heater Core Replacement on AC Car

Robert I replaced my heater core on my AC 70 a few years ago and did not encounter any damage to the heater core tubes removing/replacing the assembly. Did not remove the top dash pad.

[John M.]

Re: C3 Heater Core Replacement on AC Car

Robert - this is the article I used which helped a lot.

http://www.corvettemagazine.com/content/view/81/

John

[James W.]

Re: C3 Heater Core Replacement on AC Car

Robert,

Congratulations! You're about to embark on a painful journey! I replaced the heater core on my 71 w/air. Took out the top dash pad and it made things a lot easier. Be sure you replace all the seals in the box and ducts. Dr. Rebuild sells a kit that will work. DO not use the seals for the vent outlet balls, however, as they are too thick and the vents will not function properly - takes two hands to move them. I would up doing them twice because of this. Check all your diaphrams as well. You can get thise from the Dr., also. Good luck on your repairs.

Jim

[Robert S.]

Re: C3 Heater Core Replacement on AC Car

I am at the point of reinstalling the new heater core onto the pot metal cast plate. I have read that the plate needs to be slightly modified to mate with the non-GM heater cores that one gets today. I can see that this will be necessary but would be interested if anyone could describe the modifications they had to make to the plate before I cut any metal away.
Also I can also see I will have to rework the metal clamp that straddles the two tubes - the clamp has a single bolt to the pot metal plate. The reason is that the two tubes on the new core are slighly closer together than on the old GM (Harrison) core - has anyone else had to do this?