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Old 09-18-2005, 12:54 AM
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Question on grinding, filling, blending and seam sealing welds

We just got the car back from the welder after many many months.
One of our first tasks is grinding the welds (which he left for us to do to save money) -this is going to start in the floor pans, engine compartment, frame etc

I would like to grind the flat (panel to panel) welds down till they are almost level with the sheet metal.

Once that is done, I want to feather in body filler, so the panel joins are invisible.

I also understand I need to place seam sealer in places.

What is the best way to fill out these panel joins?

Do I place seam sealer over primed, body filled, or bare metal?

Check out my gallery for the pics of the stang coming home today

One local hot rodder suggested that I get epoxy primer, and place it on the bare metal, in places, with a brush or small roller (where it is not easily seen or sprayed)
The welder who did the car says that's not needed, just use acid etch primer, and spray it with that.

The car is not going to be painted out for a number of months. I'm confused, but after spending all this money on welding and replacing sheet metal, I want to prepare and protect the metal properly before paint.

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Old 09-18-2005, 08:34 AM
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If it were mine I'd grind down all the welds first using a 3 inch roloc and 1/4"X3" 3M hard wheel then spot blast the welds or use a klean and strip disc to clean out all the nooks and crannies. Go slow at low rpms with low pressure while grinding to avoid any heat buildup-the metal should not discolor while you grind. Then apply two good coats of epoxy primer. Use filler over the epoxy in areas that need to be blended out. Evercoats Rage Etreme or rage gold works well and in stressed areas Everglass gets my vote. Once all the filler work is done apply two more coats of epoxy. Open seams should be sealed with seam sealer over the epoxy primer and I prefer 3M's Ultrapro MSP seam sealer as it tools really nice, stays forever flexible, and can be primed and painted while wet or within 72 hours. After 72 hours it needs to be scuffed with a grey scotchbrite. After all your filler work is done and the car is sprayed with epoxy primer then you're ready for a primer surfacer either polyester or urethane. If you plan on doing some major blocking that's going to require high build I'd definately consider using Evercoat's Featherfill2G polyester primer. If she's fairly straight and you don't need any major fill you can get away with a urethane primer surfacer. Do all of your blocking with as long a block possible and use a guidecoat on every stage to see your progress.

Some prefer to use a self etch primer but if you go this route you'll need to do all of your filler work over bare metal then apply the etch primer followed by your seam sealer and primer surfacers.

What kind of paint will be applied? You may want to consider using SPI products to save a few coins while using quality products, I've never heard a complaint about anything from SPI.

Any internal seams that can't be properly prepped for primer should be coated with a rust preventative spray like 3M's rustfighter or Transtar Ambercoat, cosmoline, or similar. Some cowl areas, rocker panels, sail panels, unibody frame rails, and wheel houses are inaccessable for prep and primer- the rust preventative coating applied with a wand works well for these areas. Transtar makes a very economical 360 degree spray head wand kit that attaches to their aresol cans- I've added extensions to it and it can be fished down the length of any rocker panel interior. A case of 6 cans + the wand kit cost me about $65

You may want to strip all of the black primer off of your replacement parts if it isn't an ecoat. Wash an area down with laquer primer and see if the primer rubs off-if it does then I would definately remove it all. If it doesn't rub off than it's probably an ecoat which should be left on and only scuffed for primer. When you do any priming make sure your surface is perfectly clean and textured properly for adhesion. Refer to all product tech sheets for suggested application and prep. Hope I answered some of your questions. Bob
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Old 09-18-2005, 10:26 AM
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Very helpful , thanks

When I use a 360 nozzle to blast hard to reach places, should I do this first, or do my general paint prep and do it afterwards?
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Old 09-18-2005, 08:39 PM
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Use the 360 degree spray head on the wand for the rustfighter cavity wax type coating only on the interior of panels, this should be done after all your paintwork is done. The oils and wax in this stuff can cause fisheye problems when you paint so it's better to do it after the paint is on. Bob
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Old 09-18-2005, 09:03 PM
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Ripped,

Be careful when grinding welds flat. I dont know what the guy used to weld or if its a butt joint or lap.

If its a butt joint grinding it flat leaves virtually no strength if its the "average MIG weld". I have worked on lots of cars where just that has been done and have seen seams split/crack.

If you can I would leave a little bead on the top (not much) and then skim over it. Not knowing what your welder did is good reason to use a little precaution.

I want to add that I agree with Bobs comment on the seam sealer. He turned me onto that a couple months ago and I am not going back to my old sealers. Great Stuff.

Rich
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Old 09-18-2005, 09:17 PM
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Hello Rich, how is the Z comming along? I bet you're into the final blocking now. Bob
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Old 09-18-2005, 09:44 PM
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One thing I noticed, when looking over the Mustang tonight, trying to get a plan of attack in place; The car was sand blasted, then epoxy primered, then welded. There are a few pin holes in the trunk. There are also a few trim holes in the rockers to be filled. Lastly there are a number of areas where welding has blasted through and created a small hole.

There was a rear fender mounted antenna, which I want to delete

I am reluctant to simply bondo over, or seam seal these areas.

I was thinking of getting a welder, of my own to go over these holes. I could possibly braize them I suppose.

Any suggestions on what I should do, are more then welcome, as well as welder type suggestions,
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Old 09-18-2005, 10:02 PM
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I would NOT braze then. There is issues with brazing that you dont want to deal with.

I figured as much when it comes to pinholes. Not uncommon no matter how careful you are.

I would not hesitate to get a small sheetmetal MIG.
Rich
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Old 09-18-2005, 10:20 PM
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And Bob.........

Shell is blocked but checking fit on everything. I thought I had this done but the trunk does not fit as well as I like. So doing a little tweaking on that.

I have not touched the front fenders yet. The are NOS that I picked up at the dealer a few years ago. Hoping they dont need too much work.

Rich
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Old 09-19-2005, 06:46 AM
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Rich, I know what you mean about the trunk lid fit, they weren't very nice from the factory and there isn't a whole lot you can do without getting into some major surgery. Just a suggestion-One thing that you might want to do is put two or three layers of masking tape between the hinge and lid to simulate the paint that will be added to those areas, this will raise the lid some-the same as when the paint is applied. I didn't do that on the last one I worked on and when I reinstalled it on the car I found it setting higher than expected and then I had some major tweaking to get it right. Had I simulated the paint thickness between the hinges and lid I would have been alright. I used mock up bolts with plastic washers to get the lid dialed in then when it's on the car for good I put the correct bolts in one by one. I usually put some sandwich bag plastic over the bolt head and push the 6 point socket on over that-this way the paint doesn't get marred on the bolt heads, I've tried the sockets with the plastic inserts-they are junk IMO. ramble, ramble
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Old 09-19-2005, 10:30 AM
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Thanks Bob.

I had a couple issues. One minor and one that could have been severe.

The minor one was the curve of he trunk did not follow the quarter as well as I would like. That was a matter of laying padded blocks under the trunk and using the palm of my hand to tweak it into place. All is good with that now.

The major one was the seam between the filler panel and trunk was skewed. It might have just looked worse because the car is DP gray and the trunk was DP black. With the trunk aligned across the back and up the sides the gap on the passenger side front seemed HUGE. The drivers side look OK.

I installed new quarters on this car (NOS GM) because both sides had amateur body work done and I was concerned you could see it from the inside. I did one quarter at a time and left the trunk on when I did it. The passenger side had been skinned and the outer wheel house was wrinkled. So I replaced the outer wheel house while I was at it. Apparantly this is something that happened in 69 from a discussion with previous owner.

Anyway, I thought everything was good but when I put the trunk back on it looked like "doo doo". I might be more particular now than when I started the car. I noticed there was a slight shift in seam between the quarter and trunk filler of about 1/8". I did not think about it when installing the quarter as everything fit so nice and its a radiused seam that gets caulked anyway.

So ended up drilling the spot welds back out and cutting the brace that goes from the trunk hinge to the inner wheel house out (glad I have a donor car now) As soon as I cut that brace.. boing it came back in place. I cheated it an extra 1/16th the other direction and all is good now.

Was a few tense moments because I honestly could not see how 1/8 inch could make so much difference.

Rich
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