Rear valence attachment questions

[dreiermann]

I am installing a Euro rear valence (new sheetmetal, not cut from another car), and have a couple of questions about how to attach it:

1) At the upper corners, it was brazed from the factory, beautiful work. I had never thought about brazing stuff before - could I just weld these corners and use body filler to smooth it out, or is brazing necessary to shore up this very thin area?

2) Immediately below the taillight openings is a seam that is visible under the paint. From what I can tell after cutting out the old panel, this joint was welded from the back and then partially filled from the front. Is that correct? I want this seam to look as 'factory' as possible.

Also, any recommendations for the flexible seam-sealer used in the trunk? The original stuff must have been great - still flexible after 40 years, and clean metal underneath any part of it that I have peeled up.

Thanks!

[cgifool]

I think you'll have a heck of a time welding those areas without burning through or distorting the metal. Also even if you do manage it, the result will be harder and more brittle. Perhaps ductility there is important as well.

[Layne]

I think it's just that the area needs to be smooth for the trunk gasket to seal, yet body filler will fail and cause rust if moisture is held against it. Brazing is easy, you should just do it the right way. Here's the one I did.


Layne's iphone 4 208.jpgLayne's iphone 4 209.jpg

[Layne]

You're right about the seam, it is welded from the back. I'm not sure about a 'cosmetic' seam sealer to use... something that can be smoothed easily. It does exist, I just don't know what to buy. I did the seam with standard seam sealer and it's not that great. I did not try to find what the sealer is soluble in... pretty sure it's not water, acetone maybe. Could use a gloved finger wet with acetone or whatever (test first) and possibly wipe it smooth. I agree with you this seam needs to be right, I hate when people bondo over it.

For inside and under the trunk, standard seam sealer is fine. It comes in a caulking tube at pro paint stores. 3M and SEM are the brands at my store. Both are good, but SEM is a lot cheaper (still $15/tube though). I use an acid brush or chip brush with the hair cut short to spread it around basically like the factory did. It's pretty sticky and hard to work with, but it comes out ok in the end. The factory was pretty messy with it too. Try to use up the whole tube, it doesn't store long. And don't buy more tubes than you need.

I don't yet know of any solution for the sprayed on rubber texture they used. Standard tar undercoating in a spray can is ok for under the car (Duplicolor has the best texture of the ones I've tried), but it doesn't dry hard like the original stuff, so I'm afraid using it inside the trunk would result in it rubbing off onto whatever touches it, even if you paint over it. I'm sure this can only be replicated with a professional spray setup. I'm very interested in finding a way to do this.

[dreiermann]

Wow, looks like you had to get a lot of heat into the metal for brazing. I looked up brazing kits, they are not too expensive and I am sure that I will find other uses for it, so I will just go ahead and do it that way. What amazes me about the factory joints is how smooth they were - like they were leaded in, but with brass. As a beginner, I'm sure that I will spend a lot of time grinding brass blobs.

For the sprayed-on texture, I was going to go without for now until I eventually repaint the whole car (more than 5 years down the road). There are several manufacturers that have a "Schutz" product that are applied with a special gun - should be the same stuff that is on the lower rockers and inside the trunk, as well as the lower portions of the front and rear valences.

[Layne]

I looked up brazing kits, they are not too expensive and I am sure that I will find other uses for it

What kind are you looking at? The tiny torches with a disposable red oxygen tank and propane or 'mapp' gas are cheap and will do the job, but they aren't very good and the oxygen is way too expensive. A good option for rare or one-time use. (A propane or mapp torch without oxygen will not braze). I used a "turbo torch" which runs on acetylene and air. They work good for lots of things (mostly plumbing and AC work), but you can't cut steel with them. The torch itself is reasonably priced, but you have to buy or rent the acetylene tank and it's expensive to fill. Don't need oxygen though, and it runs a long time on a tank of acetylene. A real oxy/acetylene torch (two refillable bottles) is the ultimate of course, but expensive to buy and small ones are very costly to run. You can cut steel, but only for a few minutes per fill.

So the best option really is to borrow a torch from someone with a good one

[dreiermann]

I totally agree that the best option would be to borrow one! Unfortunately, none of my friends have one. I was looking at the Bernzomatic kit for about $60 - that is probably the one you are talking about with the disposable mapp and oxygen bottles. I will also look into the Turbo Torch.

On the plus side, if I get a torch that isn't that great, I will be less-inclined to use it for major projects, like building bicycles. That will save some time!

[okieflats]

This is the typical turbo torch plumbers use with propane. About $60. I have brazed with one using MAPP gas, stainless sheet metal 14 gauge. Takes a while to get it hot enough to melt the brazing rod.

I suppose this would be better. http://www.zoro.com/turbotorch-brazi...35/i/G1508692/

[pofo]

I will be doing the same very soon. You are right that welding could damage the panel but if done correctly it will be the best option. I plan on stitch welding at a a very high amp with a fast wire speed. Doing this you will avoid add to much heat into the panel. Also make sure you work in small sections and let the metal cool after 5 or so stitches. It's a slower process but works grate. Then also you just grind it flat and use body filler like a normal repair on the body.

Also use raptor truck bed liner for a high quality textured finish, and if you dont want black they have tintable version also.

[dreiermann]

I had thought that I was going to get to the brazing over the weekend, but forgot that I had to fit in the euro lower corners (on the sides) first - I spent most of the weekend doing that. Getting the rear valence to fit correctly is more three-dimensional than it looks, and without the lower corners in place first, the rear valence doesn't want to sit right.

Looking at the top joint and thinking about it, I decided that it would be best to tack it in place with a weld before brazing it. And looking at the shop manual, it appears that is what they recommend there.

Thinking about the different brazing torch options - the (affordable) ones that are short of a full welding torch - I was wondering if there might be a different brazing rod that would melt at a lower temperature. If the strength was slightly lower than with regular brass rod, I could back it up from behind with reinforcement. And a lower temp might allow me to smooth out the finish like the factory version, kind of like using lead filler.

[Layne]

Thinking about the different brazing torch options - the (affordable) ones that are short of a full welding torch - I was wondering if there might be a different brazing rod that would melt at a lower temperature. If the strength was slightly lower than with regular brass rod, I could back it up from behind with reinforcement. And a lower temp might allow me to smooth out the finish like the factory version, kind of like using lead filler.

There are. You could definitely use something like 15% silver solder that AC repairmen use. They don't use flux for AC, but you'll need it for steel. I don't know if you could use Borax for flux like you can with brazing (it's cheap). I use Harris black flux. The problem with that is it still melts about 1200F, and even though that's 500F less than brass, you still need the same high powered torches. You could try it with a propane/air torch (the $20 kind with the little disposable bottle), but I'm skeptical that would work well.

Unfortunately I don't know much about soft soldering except for electronics and water pipes (soft solder = less than 840F). It's generally very hard to get it to stick to steel.

[dreiermann]

After thinking about it some more, here is what I decided to do, and did, at the upper corners: 3M panel-bond plus tack welds (a lot of them) inside and outside. I was not confident in being able to get brazing throughout that joint, and would have probably really overheated the area in the process of trying. I was using panelbond/tack welds anyway, where I extended the trunk floor to meet the new valence. I will use filler (not much will be needed) to smooth it out.
Hopefully, it will hold up and not crack. Since I am not doing a primo paint job for now (just epoxy primer plus enamel color on the new panels and repair areas), it won't be too big of a disaster to re-do it later if it doesn't hold. However, now that the panelbond is in there I will never get it out and any repair would have to consist of welding in reinforcement from behind. I will update the situation when I eventually paint the whole car (at least two years from now).