Quarter Panel Replacement Question

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rackerm

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To anyone who has replaced their Fastback quarter panels. I value this group's expertise and opinion here. Although I am doing this on my 70 fastback, I am thinking the thought process here applies regardless of the model year.

With that said, I am getting ready to replace my 70 fastback original quarters with Dynacorn Skins. The skins replace the old panel from the front door jamb lip to the rear quarter extension lip, and from the rocker, wheel well lip, and drop down on the bottom of the quarter to about two inches over the top of the quarter shoulder. See the pictures below where I have just laid the panel over the old panel.

My quarters are mostly good and only need to be replaced from about halfway down the quarter, this would include the section at the door jamb/rocker in front of the wheel well, the wheel well lip and the lower quarter behind the wheel well where it meets the dropdown and the tail panel and valence.

So my question, is it best to use the entire replacement skin, which means cutting the old quarter panel over the shoulder (just below the quarter window and thru the top of the trunk deck area), or is it better to cut the old panel a few inches down the side of the panel below the top of the quarter, and trim the new skin down to meet it? Seems to me, that it would be easier to patch them together on the side of the panel where you have a more "wide-open" surface area to work it, than over the top of the shoulder where the panel curves are close to the quarter window and C-Pillar.

I would appreciate feedback, from anyone who has done this before.

Thanks











 
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turtle5353

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In my opinion both have pros and cons. If you cut it on top, the material is less likely to warp when welding because of the bend in the top of the panel. But you have less area to do the mud work over the seam.

If you cut it on the side you have a much easier chance of warping the panel when welding because of the long flat plane. But you have alot more area to work the mud over the seam.

If you're careful you can do it with out warping. That's probably what i would do. Cut out old panel, But leave a few inches to over lap at top. Use self tapping screws and clamps to hold it in place and get your fitment really close. Then use a body saw and make a cut through the patch panel and the old panel at the same time. This will give you a perfect line even if your cut is slightly crooked. Once cut is made, verify your fitment for a final time, and start tack welding. Move around ALOT. Keep a wet rag with you and cool the tacks as you go.

Also personally i always do a butt weld on the seams for a cleaner look from the inside.

Here's a link to the 71 i replaced a quarter on. https://www.7173mustangs.com/thread-new-project-for-this-winter-71-mach-1?page=4

 

Bentworker

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To anyone who has replaced their Fastback quarter panels. I value this group's expertise and opinion here. Although I am doing this on my 70 fastback, I am thinking the thought process here applies regardless of the model year.

With that said, I am getting ready to replace my 70 fastback original quarters with Dynacorn Skins. The skins replace the old panel from the front door jamb lip to the rear quarter extension lip, and from the rocker, wheel well lip, and drop down on the bottom of the quarter to about two inches over the top of the quarter shoulder. See the pictures below where I have just laid the panel over the old panel.

My quarters are mostly good and only need to be replaced from about halfway down the quarter, this would include the section at the door jamb/rocker in front of the wheel well, the wheel well lip and the lower quarter behind the wheel well where it meets the dropdown and the tail panel and valence.

So my question, is it best to use the entire replacement skin, which means cutting the old quarter panel over the shoulder (just below the quarter window and thru the top of the trunk deck area), or is it better to cut the old panel a few inches down the side of the panel below the top of the quarter, and trim the new skin down to meet it? Seems to me, that it would be easier to patch them together on the side of the panel where you have a more "wide-open" surface area to work it, than over the top of the shoulder where the panel curves are close to the quarter window and C-Pillar.

I would appreciate feedback, from anyone who has done this before.

Thanks










You will need to get a dolly behind wherever you weld to do some metal planishing.  Not that I have ever worked on a 70- but where the repop panel seems to suggest a seam looks like a good spot.  With that 90 degree bend so close, and the fact that you would be butt welding flat it seems like a good way to go about it - as long as you can get to the back side for planishing, and maybe backing it with some copper for welding it you choose to do so.  Having that bend close by is going to help with controlling warping, should be pretty easy to get it back into shape after welding and grinding with a contour gauge and some hammer and dolly work.

 
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I have not done whole panel but I do know that my friend that does them for a living and for last 35 years has two ways.

The 68 Firebird HO 4 speed he just finished will be going to the Pontiac Nationals next year, is this coming weekend I think. It will also be entered in the Nationals for just Firebirds. So for a car that is going to be shown for maximum points he does not remove the entire original panel. 

At the jam he cuts maybe an inch back of the wrap around. This gives enough room to hammer and dolly weld and leaves the factory spot welds down the jam. 

He does the same in the rear where it wraps around the tail light, GM did not have bolt on end caps. Leaves the original spot welds and original rear corner. 

When you look in the trunk he of course butt welds the panel and grinds and finishes the inside just like the outside so you cannot see or feel any seams or laps. He keeps the original bend at the belt line.

If the car is really bad rusty and he can't save the corners he drills the spots and removes whole panel. 

To do the entire quarter is tough since the roof went on after the quarter and laps over. He has cut the lap off put the piece under the roof in then put the quarter on and weld back together. 

Some of the repo panels have sharper edges and some have softer can also come into the decision.

He uses narrow belt sander when grinding his welds produces less heat than side grinder.

Here are some pics of the Firebird outside. The owner could not stand it he drove it to show in town two days after it was done. 

Besides fit the other big complaint he as with the repo is they use much softer steel. You can bend a panel if you prop your elbow on it or if someone leans on the quarter it will bend.













 

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Excellent tips.

Just patched my front fender, and if there something said above to be underlined and set in big red letters:

Wet rag, I'm always amazed how fast they dry out. No wash dryer can beat that! Make sure it's really wet before you weld. So you can apply it right after the weld.

Copper: not only it helps get the pool flat on the inside, its also a massive help to prevent holes as you can start welding on the copper (the small gap you'll get from the saw)

Especially effective on the first isolated weld you'll need to make, where on a 71-73, you'd likely have light corrosion on the original material inside (less thickness). Dip the copper in water also after each weld, as they absorb lots of heat, they'd loose their purpose if already "loaded". Been using aluminium before, but copper is 10x times better for this.

Best weapon against warping.

Some shops also have various shapes avail, so you can have a great surface of copper in contact with the 2 sheets near your weld.

https://www.vocor.nl/las-gereedschap/1801-welders-helper-3-stuks-vlak-gebogen-en-haaks-koper.html

I see you've been busy already on this project. Sandblasted it?

 

Don C

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You can also just blow air on it with your air gun, cools the thin sheet metal quickly and is less likely to cause shrinking of the metal around the weld. I've encountered some sheet metal that likes to shrink after any heat.

 

rackerm

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Excellent tips.

Just patched my front fender, and if there something said above to be underlined and set in big red letters:

Wet rag, I'm always amazed how fast they dry out. No wash dryer can beat that! Make sure it's really wet before you weld. So you can apply it right after the weld.

Copper: not only it helps get the pool flat on the inside, its also a massive help to prevent holes as you can start welding on the copper (the small gap you'll get from the saw)

Especially effective on the first isolated weld you'll need to make, where on a 71-73, you'd likely have light corrosion on the original material inside (less thickness). Dip the copper in water also after each weld, as they absorb lots of heat, they'd loose their purpose if already "loaded". Been using aluminium before, but copper is 10x times better for this.

Best weapon against warping.

Some shops also have various shapes avail, so you can have a great surface of copper in contact with the 2 sheets near your weld.

https://www.vocor.nl/las-gereedschap/1801-welders-helper-3-stuks-vlak-gebogen-en-haaks-koper.html

I see you've been busy already on this project. Sandblasted it?
Fabrice, Thanks for the tips.

Yep. Its sandblasted and with huge help from my good friend John, we have done much of the metal replacement upfront and finishing up the torque boxes, toeboard, and floor now. Installed Tinman Subframes and a one-piece seat platform to add rigidity. Next will be the quarters and dropdowns.



 

rackerm

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Hey All, Thank you so much for the excellent tips. What a big help you all are.

So another question, if I may... anyone see an advantage to TIG welding the quarters over MIG? I hear TIG will (if done right) produce less heat than MIG. I would think that would help avoid warpage along with using water, air, copper, and moving around the seam, etc.

 

Don C

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Mister 4x4

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Let me chime in as an example of what not to do.

I did both of my rear quarter skins, and quite honestly the driver side came out better than the passenger side (which was first), so I wound up redoing the passenger side with lessons learned coming into play with the first go around.

I overlap/plug welded mine, since every attempt at butt welding to that point just had me buring holes along the edges of both sides of the seams.  I also went as absolutely slow as I possibly could, and both of my attempts were "surfer delights" (wave, after wave, after wave...).  I bought a stud welder/slide hammer kit from Harbor Freight, which had almost zero effect on anything.  After trying just about every trick I could come across, I finally resolved myself to the fact that my quarters are beyond my skills and just sent them to the body shop that way.  I have no idea if they'd been smoothed out with minimal filler, or just had a bucket of mud slathered on and sculpted - and I honestly don't care.  The car is shiny again - if/when the paint & body work starts going south, I'll address it then... for now, I'm just going to enjoy what I've got.

BTW - when I pulled the passenger side off to start over, I decided to give 3M Panel Adhesive a try, in order to help eliminate the waves.  Guess what - it came out a LOT better than my welding, that's for sure.  I wouldn't hesitate to recommend that solution.

 
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It takes some practice but a torch welder made by Henrob what is now Cobra is how some shops do it. We had couple women at our stamping plant that welded up splits in body panels with them and did not warp the panel and were fast. It was an approved by Ford method of repairing panels.

The torch also works fantastic with brazing rods. 

One of the issues with MIG is that the welds are pretty hard compared to the base metal. The torch welds will be soft. If you use propane the welds are harder also.

TIG also takes some practice. 

I am going to see if I can get back into the grove with mine. When I was in high school I was good with torch and first thing I bought was a Smith's torch outfit that I still have. It is like buying a guitar you have to practice. Mine has been sitting for years so I need practice. Keeping the metal cool and also hammering the weld is the secret.

You have probably seen demonstrations at swap meets with the torch. They make it look easy and can do aluminum also. 

As you can see the picture of the box it comes with lots of tips for different things. Has a DVD and you can see that the person doing the demonstration is an artist, lol. You use much less gas than with a normal torch. You set regulators at 5 lbs.. I did also get their low pressure regulators. 

Here is link to the mfg of the torch with some questions and answers.

https://detroittorch.com/pages/faq

Demo video.

They are not cheap but we used them for years in a mfg. enviornment with no issue. Just have to learn and practice, practice, practice.





 

rackerm

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Thanks to Fabrice, Bentworker, David, turtle5353, Don C, Mister 4x4 for taking a moment to share your experience and expertise. You have all given me lots to think about as I prepare to take on this new challenge... quarter panel replacement. I will let you know how it goes.

 
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