Here is my question and potentially my new problem. I had the heater core out of the heater box to paint the outer heater box ( blower motor mounts in it). The inside box was POR 15'd on the inside where the core sits. While I was gone for a couple of weeks my body man painted the outer box and installed the core in the inner box and mounted the assembly on the car. All he did was put the original clips on that hold the core. He did not use a seal at all inside the inner box for the core. He did seal the outer box when he mounted it to the car. am I going to have issues where the heater core mounts or am I going to be alright with leaving it as is? I hope I explained the situation correctly.

Here is my question and potentially my new problem. I had the heater core out of the heater box to paint the outer heater box ( blower motor mounts in it). The inside box was POR 15'd on the inside where the core sits. While I was gone for a couple of weeks my body man painted the outer box and installed the core in the inner box and mounted the assembly on the car. All he did was put the original clips on that hold the core. He did not use a seal at all inside the inner box for the core. He did seal the outer box when he mounted it to the car. am I going to have issues where the heater core mounts or am I going to be alright with leaving it as is? I hope I explained the situation correctly.

I'd be concerned about it rattling around without a seal.

About 90% of the time when I take a heater box apart to replace a core, that square seal is either missing or was never put there from the factory. I know it's there for a reason, but it doesn't seem to effect the performance of the heater. The firewall seal is the important one you don't want to forget to put back. You will have problems such as fumes and water leaking into the passenger compartment of the car.

I kind of thought it would be alright without and thanks for the reply. I think that the body man used some sort of sealant around the edge of the box. I think it will be okay. I don't believe he used an actual gasket.

I kind of thought it would be alright without and thanks for the reply. I think that the body man used some sort of sealant around the edge of the box. I think it will be okay. I don't believe he used an actual gasket.


I don't think there is a gasket for the outside of the box. I just used Ultra black silicone.

When I had my 69 box apart, I did not notice a squarer seal between the core and the outer box. My core was held in place with two clips (funny light green). I replaced all the heater box seals and converted to a BB core. No problems. I agree the seal at the blower box (outer) to firewall is the most important.