G body A/C or heater box modification

Discussion in 'Big Block Cadillacs' started by 5one9, May 30, 2019.

  1. 5one9

    5one9 Active Member

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    Does anyone have a close up picture of a 1978-88 G Body heater or A/C box that has been cut for clearance of a 500 Cadillac? I'm just trying to get an idea of location and amount of material removal. One vendor claims to have an engine mount kit that uses the stock A/C box, but my measurements make that claim seriously questionable.

    Any help appreciated prior to me just jumping into it.
     
  2. Caddylackn

    Caddylackn Member

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  3. Cadiac

    Cadiac Active Member

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    With my engine offset aprox 2.5” the rocker (stock) cover chafed the box. I made a hole in the box to accommodate the #7 plug wire. Lol 85 GP assuming all box’s identical?
     
  4. 5one9

    5one9 Active Member

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    GP should be the same. I assume you mean offset toward the driver side?
     
  5. Cadiac

    Cadiac Active Member

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    No to the passenger side to get the exhaust away from the steering column
    You can remove the shaft from column to box and get one from a jeep wagoneer Will give a little more room
     
  6. 5one9

    5one9 Active Member

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    If I moved my engine half that amount, the head itself would hit the box, without the valve cover.
     
  7. Darius

    Darius Well-Known Member

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    Don't you just love tight spaces??? NOT!!

    bro. d
     
  8. Cadiac

    Cadiac Active Member

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    Really? Mine is still on the same mounts 21 years later, but is gutted of everything for racing only. My stock rocker cover chafed the box
     
  9. Cadiac

    Cadiac Active Member

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    I may have a video I can get a pic from???
     
  10. 5one9

    5one9 Active Member

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    That would be cool. With my engine dead center, a chrome valve cover almost bolts on but not quite. If Caddy had mirrored the bolt holes like SBC you could flip the cover around and it would clear the box and have extra rocker clearance..........but they didn’t.......
     
  11. 5one9

    5one9 Active Member

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    So, with the rockers installed (no pushrods yet) and the aftermarket chrome covers on, the covers sit flat on the head mating surface without touching the rockers anywhere. If I turn the covers around 180 degrees, I still have clearance at the roller end, even though it's the short side of the cover. A gasket will only help the clearance situation.

    With the cover turned 180 degrees I also have about 3/8" of clearance between the cover and the A/C box at the closest point, which will barely decrease with gasket installed.

    Here is the plan. I just bought a $35 set of black aftermarket covers identical in shape to the chrome ones. I will cut parallel with the mounting flange, up high before the curve on the cover's short side, all the way around the cover. Flip the top around, bolt it to an old head, and with a little body hammer work and my TIG or MIG, weld the tops back on. By moving the tall side of the cover to the intake side of the valve cover, there will be more than enough clearance at the adjuster screw for my 0.353" lobe lift.

    It won't be the polished aluminum covers that I hoped to use, but no cutting of the fiberglass box to allow the A/C to be functional will be well worth it. I will update with pics as I proceed.
     
    Last edited: Jun 9, 2019
  12. 5one9

    5one9 Active Member

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    FB4A7445-4BE3-4F4E-9752-220F5FE2B8C9.jpeg Cut and flipped valve covers today. I have about 3/8” of clearance to the A/C box and plenty of rocker arm clearance at full lift. I’ll paint them with wrinkle paint to cover the imperfections.

    Now on to the headers.
     
    50olds likes this.
  13. Darius

    Darius Well-Known Member

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    Dang!

    Nice job!

    bro. d
     
  14. 5one9

    5one9 Active Member

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    A little textured bed liner paint and blue and the work is barely noticeable.

    A41A4FB2-C95D-48EB-9DE2-400A67459AED.jpeg
     

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