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TECH:Chopping a hardtop's vent posts ....

Discussion in 'Tech Archive' started by choprods, Sep 29, 2007.

  1. choprods
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    choprods Alliance Vendor

    This is a subject that could end up in the tech archive.....if it gets noticed by anyone here.:D

    The front vent window posts on most HARDTOPS are made of a Zinc based DieCast metal,not a real Aluminum alloy.

    When you chop the top, you will have to shorten them as well...
    This has been a problem so I want to share a few bits of information here on the subject.

    The ones I am showing here are from a 50-s GM.
    It was given a 3" chop.
    First you need to plot the cuts where the MINIMUM amount of "welding"/-brazing ,is needed.
    I say this to save you trouble as this is not an easy task.


    I had done chops on these as long ago as 20 years ago, but not really much lately- so I needed to refresh my own memory as well...
    I cut the top off the posts and removed the 3" as I did on the adjoining body posts.

    The problems are multiple here -as it's a combination of things that makes these a bear to shorten...

    The vent post's metal ,is very touchy -in that -just as it reaches the melting point it is :eek: VERY NEAR the point of just melting and dropping off as a big splatter of molten metal,leaving your post an inch or two- too short!:rolleyes:

    I remembered using a propane torch the last time I"welded" these.
    I had misplaced my old one and had to buy a new one a few days ago...
    sadly it is not a very efficient one as it would not do the job at all.
    I next used my acetylene torch[I use Propane with my OXYgen].

    This proved to be hot enough at almost it's very lowest possible flame pattern:eek: .

    I used a special alloy brazing rod that combines Magnesium with the rod ...it was about 5 dollars for two 10" rods.
    Rods are Made by BERNZOMATIC.....available at most hardware and farm stores...

    they do not go very far in the process -so buy several.

    I drilled the two peices to be joined -and that was very tough as the only "flat" area is very small at best.
    This was done so I could "pin" the two in position.....using a screw in these 1/8' holes...I used one that I could bend slightly so as not to break it while final alignment is achieved.....
    It also allows you to install it on the door for fit....

    This is also necessary because the two sections are not straight or square in any of their surfaces.
    That basically prevents you simply clamping the two with clamps or vise grips well.....
    I then heated very slowly the entire peices together for a few minutes, before concentrating the flame on the splice....

    take your time and hold the heat -back -when the posts start to become molten...
    as stated above it is very touchy and can easily ruin your posts completely.....
    I then flowed the rod in the splice[1/8" wide] which ends up bein a very nasty looking glob of metal!
    I used cut off wheels to slice off the majority of the lumps -then a 24 grit sander to sand the area smooth..
    It clogs a lot so several discs are needed.
    These are welded although a long way to being ready for a plater.....

    Hope someone can use this info here -it seems not a lot of tech is posted any more....
    I wonder why that is?

    Attached Files:

  2. jonzcustomshop
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    jonzcustomshop Member

    Thank you! thank you! thank you! this was the post I needed to see!
    I have 6 or 7 vent window frames saved up for my 60 chev chop, 'cause I wasn't sure how it would go....
    this will help.
  3. zman
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    Your the man... great tech
  4. glassguy
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    glassguy Member

    this is great!!!!! i had a really hard time doing those thank you
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  5. X38
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    X38 Member
    1. Hot Rod Veterans

    Thanks for the tech! Yes, we need more of it.
  6. the shark
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    the shark Member

    i will definitely need this in the future. thank you
  7. Moonglow2
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    Moonglow2 Member

  8. TP
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    TP Member

    Chop have you ever used a "jewlerers torch for the pot metal? I used some of that pot metal rod on some 55 cameo tailites and a jewelers torch and it worked pretty well. It has a real defined small flame. Me and Adrian of the "Los chochinos" was discussing this very thing today. I've heard you can use the Henrob torch also but I never can get it to adjust right. TP
  9. breeder
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    breeder Member

    nice tech kenny! too bad im only missin all the parts to do one...you know, the vehicle, shop, talent! other then that, im good!:eek: ;)
  10. choprods
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    TP...a jewler's torch is the schiznitz for that thin trim...But the thick posts at mid point and on up are thicker than it can EVENLY heat....that is why a full size propane torch would not achieve the task......
    I use propane in my torch with oxygen, that would be a little less heat than acetylene I think-right??
    Anyways -be cautious guys ,as it is very EASY to botch this weld job.....
  11. choprods
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    Forgot to mention,You will need to grind off the chrome an inch or so from cut and bevel the edges of both peices,this helps adhesion properties of the weld/brazing rods......
  12. choprods
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    BACK- TO THE TOP.........
    The tops of each vent glass's steel frames needed to be extended longer... [to line up at the back edge with the bottoms]....

    I used a scrap off a 49-51 Mercury Qtr side window frame....
    a lot of 49-54 cars used the same V profile channel in these frames...

    Does anyone here like seeing TECH any more, or should any of us posting it just give up?:D:cool:
  13. Moonglow2
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    Moonglow2 Member

    Kenny - I have been wondering why we have so few tech articles lately. They are mainly what I like about this forum.
  14. Unclee
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    Unclee Member

    I thrive on tech! Thanks bro.
  15. lucky
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    lucky Member

    thank-you!!!!!!!!!!!!!!!
  16. fitzee
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    fitzee Member

    Thanks Choprods for the link to this post.Great info. did you relocate the hing points for the vent glass or did you leave them as is?
  17. Pro Stock John
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    Pro Stock John Member

    I was talking to Matt today about this stuff, this is a great thread.
  18. choprods
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    choprods Alliance Vendor

    Is there any chance this needs to be archived in the tech archive or does the Tech editor not love me........
  19. choprods
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    Guess not........
  20. gmpartsgod
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    gmpartsgod Member

    Thanks....this will save a bunch of vnt frames from the trash..
  21. IowaMercMan
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    +1 on liking more tech.

    And ++ on putting this in the tech archives. Thanks for taking the time to post and explain, Kenny.
  22. choprods
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    Hi Walt,did you notice the post date on this?

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