Heater Box Seals-65 Corvette Non-A/C 350 HP (Long) - NCRS Discussion Boards

Heater Box Seals-65 Corvette Non-A/C 350 HP (Long)

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  • Richard L.
    Very Frequent User
    • May 31, 1988
    • 156

    Heater Box Seals-65 Corvette Non-A/C 350 HP (Long)

    Replaced Heater Core in car last month...Ever since, I've been getting alot of radiant heat emanating from the Inner Heater Box on the car...so much that I'm going back and looking at the installation procedures that came with Doc Rebuild's Heater Box Rebuild Kit to make sure that I didn't do something wrong. The heat can be felt near the Inner Heater Box area where the Heater Core is actually physically located, and the heat is NOT coming out of the Heater Box distribution floor duct outlet(s). I have checked all of the seals (inner and outer) to make sure they didn't roll up or get kinked and they are fine. I also looked at a past article in the Corvette Restorer about the Heater Core R&R procedure and I did notice one discrepancy between the magazine article and Doc Rebuild's installation instruction sheet (which is very good, BTW). The discrepancy exists betweeen the articles for the two Core Pipe Seals (Donut Seals) that slide over the heater core pipe nipples. The Restorer article says they are installed BEFORE the outer box cover is installed (if I'm reading it correctly) and Doc Rebuild says they are press fitted over the heater core pipes AFTER the outer box has been mounted to the firewall, and that they (the seals) are squashed by the heater hoses after installation. Opinions requested, please sirs....I did mine like the Doc Rebuild instruction sheet says and I'm wondering if I'm getting possible air blowby into the heater box areas through potentially unsealed areas.

    One of the other items I'm not sure on is that Doc Rebuild's Kit says that for midyears, sometimes TWO Outer Heater Box Seals are used and sometimes only ONE Heater Box Seal is used in this area. The instructions don't offer any more assistance on why some cars used one seal and why some used two seals. When I took mine apart it only had one seal so I went back with just one seal. The only deal is that the heater core had already been replaced once and I don't know if it originally came with one seal or two seals installed on the Outer Box firewall. If anyone could shed some information on this matter it would be most appreciated, as well.

    Obviously, I will be calling Doc Rebuild to get a little bit more information on these issues but I thought I'd poll the masses and get some real world opinions on this matter, as well.

    It might be possible that the old heater core could have been so restricted or partially plugged that since I now have a new heater core this may well be the way it is supposed to operate. Since the midyears W/O A/C weren't equipped with vacuum operated hot water shutoff valves, radiator water gets pumped through the heater core all of the time. If I can feel radiant heat in January, what is it going to feel like in July-August...

    For my own knowledge, should any type of sealant or adheisive been used on the Outer Box Firewall Seal??? Also, once the Outer Box was installed, is any type of dum-dum (sealant) supposed to be run on the outside seal area of the box where it meets the firewall??? Again, any assistance here would be most apprecitated...

    Thanks In Advance for any and all help...

    Rick #13174
  • John H.
    Beyond Control Poster
    • December 1, 1997
    • 16513

    #2
    Re: Heater Box Seals-65 Corvette Non-A/C 350 HP (L

    Rick -

    The heater installation sheet in the A.I.M. (UPC 1-ASM, Sheet E5 in the '65 Manual) shows three or four continuous sealer applications between the inner and outer seals, gaskets, and dash panel, and 67's also got a sprayed-on gooey sealer around the joint between the blower case and the dash panel on the engine compartment side - don't know when that started, but it should show in the '67 A.I.M. (I only have the '65 Manual).

    Comment

    • Duke W.
      Beyond Control Poster
      • January 1, 1993
      • 15643

      #3
      Re: Heater Box Seals-65 Corvette Non-A/C 350 HP (L

      All these old GM non-a/c cars constantly circulated hot coolant through the core, so the housing got warm to hot, and some warm air came out the air nozzles.

      Could be your last statement was the key - the core could have been clogged to the point where little water was circulating through.

      I've found that the only viable solution is to install a heater shut off vavle somewhere in the hoses and keep it closed during the summer months.

      Duke

      Comment

      • Geoff C.
        Expired
        • May 31, 1979
        • 1613

        #4
        My thoughts

        Rick

        1. Big lip flat speed nuts not tight enough to squeeze both boxes together on either side of firewall.
        2. Two biggest Black rectanguler seals on same side of firewall - instead of 1 on inside, 1 on outside.
        3. Cable controlling door right behind core is not closing door completely leaking.
        4. You other non-air car is also plugged, so you don't notice it there and if it is hot in your AC car - you put on the air.
        5. Liquid "Rubbery" Black" sealer slop" is sprayed on the outer firewall to seal everthing better back then - right over the outer box - but from the heat you describe - lacking this "slop" would not account for quantity of heat you are describing.
        6. Definite solution: sell non-AC, buy another AC model. I will not buy any Vette without AC unless that model did not come with AC. (any 435, L89, L88, FI, pre62 must be convertible or a steal).

        Woody

        Comment

        • Richard L.
          Very Frequent User
          • May 31, 1988
          • 156

          #5
          Thanks, John, Duke and Geoff.....

          I'm gonna do a little bit more investigative work tomorrow PM and I'll give an update....Geoff, I can't afford the L88 right now so I'll have to work on my small block and get it right....

          Rick #13174

          Comment

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