504 rear guard
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Thread: 504 rear guard

  1. #1
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    Default 504 rear guard

    We've had a '73 TI for about a dozen years. It has been treated as a work horse and is looking a bit scruffy, but it is still a sound car with no serious rust. Lately I have been warming to the idea of fixing it up, outside and in.

    Of course it's only when you scratch the surface (literally) that you find what the job really entails. Evidently this car had a hefty hit on the left at some stage, I suspect both doors have been replaced, but the worst is the rear guard which has had the panel pulled out to a diseased approximation of standard, with inches of body filler applied. A lousy repair, but quite a fetching sculpture.

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    Is there a standard way of fixing the rear guard? I'm guessing that I need to get a section from a wrecker, but where should I cut? The damage is worst at the door gap, and is straight at the petrol flap, and it extends from the guard flare up to the roof pillar.

    My POA is to:


    • Drill out the spot welds at the door join and guard flare
    • Cut at the join with the pillar
    • Cut in front of the petrol flap
    • TIG (or maybe MIG) the suitably adjusted donor section in

    This will be the first time I've had to remove a fixed panel like this, so I'd welcome any advice. E.g. the roof pillar looks like it is brazed to the guard, so TIG right there probably isn't too clever. Better to cut higher up, or should I replace braze with braze and hit it with the oxy?

    The other thing I'd really appreciate is suggestions where I can get the donor section. I'm in W. Sydney and the wreckers around here aren't too flush with 30yo French gear.

    Have fun,

    Rob.

  2. #2
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by robs View Post
    We've had a '73 TI for about a dozen years. It has been treated as a work horse and is looking a bit scruffy, but it is still a sound car with no serious rust. Lately I have been warming to the idea of fixing it up, outside and in.

    Of course it's only when you scratch the surface (literally) that you find what the job really entails. Evidently this car had a hefty hit on the left at some stage, I suspect both doors have been replaced, but the worst is the rear guard which has had the panel pulled out to a diseased approximation of standard, with inches of body filler applied. A lousy repair, but quite a fetching sculpture.

    Is there a standard way of fixing the rear guard? I'm guessing that I need to get a section from a wrecker, but where should I cut? The damage is worst at the door gap, and is straight at the petrol flap, and it extends from the guard flare up to the roof pillar.

    My POA is to:


    • Drill out the spot welds at the door join and guard flare
    • Cut at the join with the pillar
    • Cut in front of the petrol flap
    • TIG (or maybe MIG) the suitably adjusted donor section in

    This will be the first time I've had to remove a fixed panel like this, so I'd welcome any advice. E.g. the roof pillar looks like it is brazed to the guard, so TIG right there probably isn't too clever. Better to cut higher up, or should I replace braze with braze and hit it with the oxy?

    The other thing I'd really appreciate is suggestions where I can get the donor section. I'm in W. Sydney and the wreckers around here aren't too flush with 30yo French gear.

    Have fun,

    Rob.
    I'm not exactly sure how 504s are assembled but I believe the rear quarter joins under the boot seal, in line with the edge of the rear windscreen and over the rear door pillar. The full manual should detail how the hull assembles.

    Unless you are an experienced panel beater I would try avoid removing the quarter and probably try repair the existing.

    504s are quite thick steel so you should be able to shrink the panel back to being tight (I prefer a "slapper") after that it's a matter getting the correct shape back into it.

    If you are a competent oxy welder you may be able to cut a section from a donor vehicle and weld it back in.

    Make sure the infil panel is accurately cut with minimum gap. Cut a strip from one of the scrap panels to use as a filler rod.

    Clamp the panel in place and tack with a few a beads. Then weld 50mm sections, leaving 50 mm unwelded and so on. Finally come back and weld the missing section. Excess heat is to avoided because the panel will buckle. I use a BOC Comet #10 tip and strip of panel about 3mm wide. Even then it want's to blow through if don't move quite fast.

    Make sure you remove ALL of the body deadening and carpet and insulation, otherwise a boot fire is assured at least convenient time. I would also be mindful of where the petrol tank is located as well.

    If you don't have four hands, a second set of hands with a hammer on the front and dolly at the back used immediately after welding (whilst still dull red) is helpful to flatten the weld and minimise buckling. Hammering now will also reduce the amount of leveling needed with the body file, later.

    If I were doing the repair, I would try to repair what you have first. I suspect changing the quarter or welding a piece in may be a lot harder.

    EDIT: Any welding is best done with a filler rod that is same as original steel. If you feel happy welding such thin sheet (about .8 mm) TIG should be OK. Lots of people use MIG, but I find the welds are too hard to body file.
    Last edited by robmac; 15th December 2010 at 03:47 PM.

  3. #3
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    Thanks robmac. You've at least half convinced me.

    As a step up from my elegant word picture of the damage, I'll include a few photos:

    504 rear guard-lr504rq01.jpg 504 rear guard-lr504rq02.jpg 504 rear guard-lr504rq03.jpg

    So I exaggerated a bit on the "inches of body filler", but you can see that the previous repair was pretty rough hackwork.

    But, with the very limited access behind allowing little more than pry-bars, I don't see how I can improve greatly on this repair, particularly at what should be a nice sharp corner near the door latch.

    Given that there is also some rust at the guard flare, I'm thinking of having a go at a half-way approach. Drill out the spot welds on the guard and door jamb, and be a little generous in what I cut away of the rust, hopefully giving me room to get hand and dolly in behind. BTW, agree on the slapper -- besides being the best named of the weapons, it is pretty forgiving and generally leaves things better rather than worse.

    And thanks for the welding tips. I rate myself as reasonably good with oxy, but have always been bothered with the distortion. I have never taken a shine to MIG -- it's all too rushed and, as you say, the bead is pretty obtrusive. I first tried TIG briefly in 1980, but hadn't used it since then. I recently equipped myself with one, and it seems to be the best of both worlds -- the control of oxy, the concentrated heat of arc. Still, it is finnicky and punishes each wobble with a walk to the grinder. All good fun.

    Have fun,

    Rob.

  4. #4
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    Quote Originally Posted by robs View Post
    Thanks robmac. You've at least half convinced me.

    As a step up from my elegant word picture of the damage, I'll include a few photos:

    Click image for larger version. 

Name:	lr504rq01.jpg 
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ID:	10942 Click image for larger version. 

Name:	lr504rq02.jpg 
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Size:	91.3 KB 
ID:	10943 Click image for larger version. 

Name:	lr504rq03.jpg 
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ID:	10944

    So I exaggerated a bit on the "inches of body filler", but you can see that the previous repair was pretty rough hackwork.

    But, with the very limited access behind allowing little more than pry-bars, I don't see how I can improve greatly on this repair, particularly at what should be a nice sharp corner near the door latch.

    Given that there is also some rust at the guard flare, I'm thinking of having a go at a half-way approach. Drill out the spot welds on the guard and door jamb, and be a little generous in what I cut away of the rust, hopefully giving me room to get hand and dolly in behind. BTW, agree on the slapper -- besides being the best named of the weapons, it is pretty forgiving and generally leaves things better rather than worse.

    And thanks for the welding tips. I rate myself as reasonably good with oxy, but have always been bothered with the distortion. I have never taken a shine to MIG -- it's all too rushed and, as you say, the bead is pretty obtrusive. I first tried TIG briefly in 1980, but hadn't used it since then. I recently equipped myself with one, and it seems to be the best of both worlds -- the control of oxy, the concentrated heat of arc. Still, it is finnicky and punishes each wobble with a walk to the grinder. All good fun.

    Have fun,

    Rob.
    Hi Rob,

    It already looks a bit like spotted dick- someone has clearly had fun and games getting it to that stage.
    I assume the circles are either weld and pull studs or drill and pull studs.

    The traditional way to repair would be to hammer/dolly out the lumps and bumps and then finish off with a dolly and slapper and finally a body file.

    That's not an option with very limited rear access. You may (any the may is very conditional) get a spoon dolly in if you drill and tap a handle to it. The surface is probably good enough to get a slapper straight on to it and try to bring up the dimples a bit. But there is no way you will get file finish.

    To be honest, this is why I love modern filler and nice dense two pack spray putty. I think you may be best to get like it as well because without removing the quarter you probably won't do much better than you have.

    cheers and best of luck

    Robert

    PS If you were in a TAFE auto body workshop you make a replacement piece and roll to shape on the english wheel, joddle the edges and TIG it in - but for the rest of us, in home workshops, we do the best we can...
    Last edited by robmac; 16th December 2010 at 01:50 PM.

  5. #5
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    Quote Originally Posted by robmac View Post
    Hi Rob,

    It already looks a bit like spotted dick- someone has clearly had fun and games getting it to that stage.
    I assume the circles are either weld and pull studs or drill and pull studs.
    Drill and pull by the looks, and the holes left afterwards.

    Quote Originally Posted by robmac View Post
    PS If you were in a TAFE auto body workshop you make a replacement piece and roll to shape on the english wheel, joddle the edges and TIG it in - but for the rest of us, in home workshops, we do the best we can...
    That was why I was asking about sources for donor panels. Should be possible to reduce the work considerably if I can get something off a 504 that's totalled on the RHS (say), but where to find one?

    Anyhow, without a donor, and given that I have to cut the flare for rust repair anyway, I'll try to make access from below and that may allow me to get things a bit closer. Oh, and great advice about the full manual -- I grabbed it at http://www.504.org/technic_GB.htm and it makes clear many mysteries. Many thanks too for the good wishes.

    And maybe I will end up making friends with the spray putty.

    Have fun,

    Rob.

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