Frame Boxing?

Discussion in 'The ragtop shop' started by SDJHAWK, Jun 19, 2015.

  1. SDJHAWK

    SDJHAWK Member

    Hello Everyone,

    I have grandma's 1971 Skylark Custom convertible and it has a bad frame. I have the opportunity to pick up a 1971 coupe frame locally for a replacement. My questions are: 1. Is there a standard way to box this frame? 2. Are there any schematics available that I can use as a template? Now the curveball, I would like to drop a in 455... someday, so I would like the frame to be strong enough to handle the engine. Any and all help would be greatly appreciated.

    Matt
     
  2. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    What you can do is cut the boxed section out of the convertible frame and have it welded or weld it to the coupe frame. Usually that part of the convertible frame is the last part to rot out, and any bad sections that may be rusted thru from the boxed section you cut off of the convert frame can be repaired and fortified before its welded on the coupe frame. GL



    Derek
     
  3. DeanTX

    DeanTX Silver Level contributor

    I got the pre-cut kit from ABC Performance. $200 and you get plates for the non-boxed sections, so you end up with a fully boxed frame.
     
  4. Duane

    Duane Member

    "What you can do is cut the boxed section out of the convertible frame and have it welded.......to the coupe frame."

    Matt,
    I have done this many times, and it works great. It takes some time to trim/clean up the edges of the boxed section, but they go in like a glove, and you cannot tell them apart from factory when finished.

    I even used a set of boxed sections off an El-Camino once. I cut the extra 4" off the back section, welded them back together, then welded them to the frame.

    The trick is to mount the pieces to the frame and bolt the trans cross member in before welding. That way you won't weld the sections too far apart.

    Its a cake job.
    Duane

    PS. The other thing to consider is this, if you use original pieces the brake & fuel lines will fit and mount to the original holes. If you use some aftermarket pieces you will have to fabricate your own lines, plus if you ever decide to sell it, it might be difficult to do once someone sees an altered frame.

    The convertible bodies need the boxed frame for structure. It's bad enough to change a frame out once, but having a new owner consider changing it out again, might really hurt the sale. Best to do it right the first time.
     
  5. SDJHAWK

    SDJHAWK Member

    Thank you all. I would slice and dice my existing frame, but it is so weak that I can not even get it on a lift, talk about saggy. I like the look of the ABC Performance kit, but do any of you think the frame needs additional support for the 455? I would rather over build and end up with a really stiff frame than have to go back and re-support it later. finally, looking at the ABC inserts, would you recommend cutting out and using my old crossmember mounts (the cross member is 2 years old) or going with the ABC crossmember?
     
  6. DeanTX

    DeanTX Silver Level contributor

    I would not think twice about the need for boxing on a convertible, unless you don't want your doors to close. On the crossmember, once you box the frame, there is a surface to mount the crossmember. Just weld in 1 1/2" angle on each side as a shelf for the stock crossmember. Drill the two holes on each side and you are done. I would leave an extra 2" of length in the angle iron for any adjustments.
     
  7. hugger

    hugger Well-Known Member

    Reinforcing the rear upper control arm.mounts is a good practice also, ive.had to.weld up.a few of those that cracked or even broke off over the years
     
  8. staged70

    staged70 RIP

    I think Duane's advise to use your boxing section on the good coupe frame would be best if its not rotted. If it is then either look for a Arizona/Utah/Oregon/ Nevada/California/Texas/ New Mexico/Colorado convertible frame. The after market reinforcements are fine but as mentioned may hurt resale value. The best fix is original parts if you can find them
     
  9. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    OR;

    You can look at '70 to '72 Grand Prix and Monte Carlo frames if the frame in front from the core support to behind the front wheels is still good on your convert you can weld the 2 together from that point and you'll have an A-body convertible frame.

    Usually the front section of the frame where the suspension and engine bolt to is the last to rot out. If that is the case then one of the cars mentioned above with the front section of your convert frame will make what you need.


    There was a junk yard in Pennsylvania that I bought a convert frame from and that's how they were able to sell nice rust free convertible frames, they would cut the front section off of the mentioned cars frames and weld on an A-body front frame using a dedicated fixture to make sure they came out right when they welded them together.(they sold a lot of them)

    If the front of the convert frame is toast as well you might find a '70-'72 Grand Prix or Monte Carlo frame and cut the front of the coupe frame you bought or are buying and the front of one of the 2 car frames mentioned and weld or have welded the front of the coupe frame to the GP/MC rear frame. Or try to find the yard in Pennsylvania that sells the frames that way if they still do that? I remember that they were close to New Castle, its been at least 10 years since I bought a frame from there so you would have as hard of a time as me trying to find it.

    Or you could cut off the box part of the GP/MC frame and weld that to the coupe frame?GL


    Derek
     
  10. Duane

    Duane Member

    If your sections are rusty then you could buy the coupe frame and then buy a pair of "boxed" sections off a convert or El-Camino frame.

    Quite often people cut off and sell just the convert boxed sections from damaged frames. You could also use the El-Camino section and cut off 4" as described on my earlier post.

    This would allow you to have a completely solid "new" frame ready for when you do the swap. My only concern is this, if the frame is that bad what do the floors/body braces look like.

    Believe me, I have done some extensive rust work in my day. Check out the repairs I did on my 70 Chevelle convertible.

    The thread on this board is titled "Some of Nicks work (Warning-Not Buick)".

    Duane
     

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