1-800-551-4754 Bodywork on your Firebird is the most important part of your restoration. For many enthusiast restorers, it’s the most challenging part of restoration and the results are critical to the quality of the overall restoration process. Think of the body as the foundation of your house. If the foundation is not solid, everything else attached to it is compromised.
The Firebird, or second-generation, F-Body car is a unibody vehicle, and therefore the body is constructed as one unit. The floors, rear frame rails, inner and outer wheelhouses, quarter panels, trunk floor extension panels, rocker panels, rear body panel, roof, and cowl are all welded together to form this one unit. Any of these parts that become compromised due to accident or rust require proper repair procedures to maintain the structural integrity of the body.
These cars have had at least 35 years of ownership and road history. Most of them have lived an interesting life . . . if they could only talk. As most people suspect, and as many experienced owners know, these cars often possess and hide many problems. Many things have happened over the course of these years, and this includes overaggressive use, accidents, and excessive rust. In some cases, routine maintenance has been almost or completely ignored, and this has significant consequences. It means you have more to repair and restore. In addition, some cars may have been improperly stored, and this leads to more rust and mechanical problems.
The importance of bodywork cannot be stressed enough. The overall quality of the restoration is largely determined by bodywork underneath the paint. The quality of the bodywork is evident in this 1970 Formula. The paint has been applied and wet sanded; the results are beautiful. The fender is installed and will be aligned.
This Tech Tip is From the Full Book, TRANS AM & FIREBIRD RESTORATION: 1970-1/2 - 1981. For a comprehensive guide on this entire subject you can visit this link:
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Taking all of this into consideration, you need to be well aware that many cars have been repaired, restored, and in some cases messed up over the years. In my experience, the vast majority of repairs are substandard. You need to correct that substandard work while you are at it so the vehicle has a consistent overall look when your restoration is complete.
The doors, trunk lid, and front sheet metal need the unit body to be in proper shape for them to correctly work. Four 15/16-inch bolts hold the front subframe to the underside of the forward portion of the floors and directly under the firewall, which requires the body to be square or it throws off the alignment of the front suspension and sheet metal as well as the engine and transmission.
Safety
Safety cannot be compromised. The whole point is for this process to be enjoyable for you and for you to enjoy the car when it is finished. Missing a finger, a limb, becoming visually impaired, partially paralyzed, or dead will not help you enjoy your car. Using the proper safety equipment such as welding gloves, a good-quality auto-darkening welding helmet, safety glasses, and the proper tools to do the particular task are important. Using a dust mask, paint respirator, and well-ventilated areas are also critical to maintaining a safe environment. Make sure you are not welding near open combustibles, as the fumes are what explode, not the liquid. Always use common sense and read the warning labels.
Make sure you clean up properly and allow time to do so before stopping for the day. Never keep working when you’re tired because it is too easy to make a bad call or have an accident when you are tired. Never work under a car without using jack-stands underneath. The coil springs are under immense pressure and can pop out of the control arm and cause major physical harm and death if one loosens. Do not assume that if a mechanic makes a particular procedure look easy that it really is easy.
Don’t wear open-toed shoes; wear steel-reinforced work boots. Wear non-flammable clothing and long-sleeved shirts. Keep your hair out of the way. Make sure you wear gloves, especially when handling flu-ids and chemicals. A majority of the chemicals with which you’ll come in contact will absorb through your skin on contact and can make you very sick very quickly. Make sure you have at least two sufficiently sized Class B fire extinguishers in each end of the workspace.
Preparation
This chapter discusses the most common rust issues Firebirds have and the proper procedures to deal with rusted areas as well as superficial dents. I do not believe in replacing entire panels unless absolutely necessary. Think of replacing panels as overly invasive surgery. Why cut more than you need? The original sheet metal is unquestionably the best to have, so why remove more metal than you need to?
The bodywork procedures I discuss will make for a proper and long-lasting repair. I cannot emphasize the importance of these steps to ensure a good-quality repair as well as stunning results once your Fire-bird is painted. Prep is paramount when working on the body and the paint reflects that hard work.
After all, the paint job is only a reflection of the level of bodywork and prep performed.
Tools for Bodywork
Performing bodywork is an acquired skill. Although a beginner can learn this skill, body panel replacement techniques and welding are not skills that are learned in a day. That’s why you need to assess and accept what you can reasonably accomplish on your own.
To perform body repair and restoration procedures yourself, you need to rent, borrow, or buy a fair number of specialized tools. You should have a full selection of crimpers, formers, notching tools, an anvil, a bench vise, and metalworking hammers. A basic kit that includes dollies, shot bags, bossing mallets, and hand-held shears costs $200 to $500. Remember, with tools, you get what you pay for; high quality does not come cheap. You can purchase these tools from Snap-on, Sears, Eastwood, Jegs, and a number of automotive supply stores.
Beyond the specialty metalworking hand tools, you need a compressor to run the air flange and punch tool. In addition, you need a MIG welder and a high-quality welder from Lincoln, Hobart, Miller, or another brand; it can cost $900 or more. And of course, when welding, a weldor’s mask and gloves are always essential apparel.
If you’re restoring one car, my recommendation is rent or borrow the tools needed to complete the restoration job. If you plan to restore several cars over the coming years, investing in all the tools necessary to complete more serious restoration jobs is most likely worth it.
Quarter Panel Patch
Firebirds are known to commonly rust behind the rear wheels, especially where the lower portion of the quarter is joined to the trunk extension panel. It is important to evaluate the rusted area and to find where the weakened metal ends and the good metal begins. It is a good idea to cut at least 11⁄2 inches into the solid metal when making a patch. When welding, you need to be sure there is no burn-through because of compromised metal integrity.
Look inside the trunk at the back side of the quarter panels to find any evidence of prior work, such as a line of newer metal indicating where a prior patch may have been made. Also look on the underside of the top of the quarters because larger patch panels generally end at the transition from the side to the top.
Most body shops do not take the time to hide the inside line that is left when doing patch panels, but if you do not see one, that does not mean it has not been patched. It just means that the seam may be hidden or just out of view due to other panels blocking it.
In almost all cases, the three- and four-decade-old 1970–1981 Firebirds need some body panel replacement because after such a long period of time, rust almost inevitably sets in. Bodywork requires metalworking and welding skill; you cannot become proficient overnight. But certainly, these skills can be learned with discipline and practice. In this case, the amount of rust warranted a quarter panel replacement.
1974–1981 Component Removal
Open the trunk lid and remove the two 3/8-inch nuts for the side-marker lights using a socket. Remove the lightbulb socket with a slight twist and pull. The lamp comes out from inside and the lamp bezel comes out from the outside.
Two 7/16-inch nuts hold the spoiler ends. They are located at the top of the quarter panel; remove them from inside the trunk.
Remove the license plate lamp lens. Remove the two Phillips-head screws with a Phillips screwdriver, and twist the bulb retainer, then remove it.
Remove the three taillight bulbs and one reverse lamp bulb by twisting the sockets from inside the trunk. Remove the taillight assembly 7/16-inch nuts (eight total) from inside the trunk. The lamp lens and outer trim are now loose and require some wiggle and twist to remove from the rear body panel. It may be necessary to rotate the top out slightly to allow the lamp to clear the bumper cover.
Next, remove the two 7/16-inch nuts holding each end of the bumper cover to the quarter panel. They are accessible from the underside of the trunk at the quarter panel ends.
Remove the two 11/16-inch bumper bracket nuts, which are accessible from inside the trunk.
Here, the rear bumper, spoiler, and taillight have been removed in preparation for body-work. Firebirds often develop rust around the rear spoiler, particularly if they have not been sealed correctly. In addition, it’s not unusual for Firebirds to rust on the rear body panel or in the trunk.
1970–1973 Component Removal
The 1970–1973 Firebirds were equipped with a chrome rear bumper, smaller taillights, and a fiberglass finish panel, so these components need to be removed. The spoiler and side-marker removal procedures are the same, but taillight and rear bumper steps are slightly different.
Place the jack under the center portion of the rear axle and use it to raise the rear of the car; raise it high enough so the rear tires clear the ground by 4 to 5 inches. Place jack-stands under each end of the rear axle and then lower the floor jack. It is important to have the weight of the car on the suspension and not on the body when replacing panels.
Two additional 11/16-inch nuts for each side sit below and behind the bumper on the rear body panel. Slide the bumper straight back and place the bracket facing down so the cover does not get damaged.
Brackets hold the rear bumper to the vehicle. They are easily accessible from the trunk.
To remove the quarter panel, taillight assembly, finish panel, and related parts, use a 7/16- and 9/16-inch socket and ratchet. Two 9/16-inch bolts hold the outer brackets on the quarter panel side while two 9/16-inch bolts hold the back side outers. A single 9/16-inch bolt holds an inner rear bracket on each side. The taillights are held in with six 7/16-inch nuts on each side: three on the top and three on the bottom. The finish panel also has four 7/16-inch nuts. The license bracket is held in with two 7/16-inch bolts accessible from the outside lower edges. The bracket also holds the finish panel in place. The taillight sockets are held in below the lamp housing. They twist to remove, as do the side-marker lamp sockets. The rear bumper has six brackets attached to it.
You need to reach inside the trunk to remove the bolts that secure the bumper to the car. Like many bolts, these can be very rusty and may require application of a lubricant such as PB Blaster. This rear view of the bare body panel also includes the back side of the rear bumper and its brackets.
Rear Quarter Panel Rust
Remove the wheel-opening molding (if equipped) and eight Phillips- head screws. Cover the exhaust tip extension with a couple of masking tape wraps so it is not damaged while you work in the vicinity.
With a 24-grit wheel, start grinding where you identified the prior patch (as in this case) along the seam. If you could not identify a prior seam, start grinding around the rusted area and work your way out until you see solid metal. You may be grinding through a white powdery substance, which is body filler. Keep grinding through that until you hit metal. Think of this procedure as exploratory surgery.
Check the inside of the trunk and the drop-off areas for any rags or flammable objects before cutting the body to minimize the possibility of a fire. Also make sure the vehicle does not have any fuel leaks. Have a suitably sized Class B fire extinguisher nearby.
Now you can see how thick the body filler is and also where the metal is sound on the remaining panel so you can trim the replacement quarter panel patch to fit once this area is properly prepared. As you can see here, substandard prior repairs have compromised the panel behind the quarter panel. This panel is called a trunk extension or a trunk drop-off. Trunk extensions are extremely rust-prone and may require replacement.
Trunk Extension
The trunk extension panel is part of the trunk floor. One side attaches to a flange at the floor; the other side ties into the bottom of the quarter panel and also has a flange. The forward portion attaches to the rear of the outer wheelhouse. The rear portion attaches to the rear body panel. This is an important part of the structure of the body. This panel usually rusts behind the quarter panel and is not visible from the inside of the trunk. Therefore, it is commonly overlooked.
Patch Panel
A trunk extension replacement quarter panel patch is not of great quality and often needs some minor reworking to make it fit and function as original. Having access to a shrinker and stretcher is helpful. This is a difficult skill to master. If you do not have access to a shrinker and stretcher, you can use a hammer and dolly to get the shape you need once the panel is installed.
Most sheet metal for patch panels is 16-gauge, but the thickness can vary depending on the manufacturer. These patches are generally available for about $50. Using the stretcher part of the tool is a matter of inserting the panel and working the metal with the handle to stretch the metal.
The same goes for the shrinker to make the curve that you need. It takes multiple times to place the panel on the body panel to com-pare your progress. Small steps are necessary because you really do not want to go too far too fast with this procedure.
The procedure works by trial and error. Starting out with just some scrap sheet metal gives you the feel and technique necessary to figure out how the tools work. Practice will make you much more proficient.
Place the patch panel in the proper position. Use body clamps to clamp it down, and make sure all mating surfaces are flush. Body clamps are available in small, medium, and large sizes and you should purchase an assortment. Almost any tool supplier (Eastwood, Sears) carries them. Make sure you have at least 10 clamps because every panel will use a different number of clamps to hold it.
Whenever you are mating a replacement panel to an existing panel, you must have enough clamps to hold the panel in place correctly to allow for proper welding. Once you have welded in the patch, be sure to look at the panel from all angles and adjust your clamps as necessary until you are satisfied that you have the panel sitting in the right place. You can obtain the anti-heat compound from many sources, including Eastwood.
Trunk Extension Patch Panel Installation
Step 1: Evaluate Patch Panel
Measure and trim the patch panel. It is important to make sure you do not cut off too much metal. Use a marker to draw a line to follow with the cut-off wheel.
Step 2: Cut Quarter Panel
Many second-generation F-Body cars no longer have solid sheet metal below the paint on the rear quarter panels, and rust may be poking through. This 1978 Firebird had a lot of body filler; I had to cut through it to find solid metal all the way around. I had previously tested the area with a magnet and knew I had a lot of filler to deal with. Simply rapping your knuckles on the panel tells you if it has a lot of filler. When you rap the panel and hear a thud sound instead flying metal shards. Also make sure that no flammable fluids or rags are in the general vicinity. Once you start the tool, slowly lower it into the metal and smoothly push the tool along the line. Use a cut-off wheel on a pneumatic rotary tool to make the first cut. It should be about 2 inches below where you designate the final cut across the top of the sheet metal. Remember, if you remove too much sheet metal you may need to replace the entire panel.
Step 3: Mark Your Second Cut Line
Once again, measure several times and make sure your lines are accurate. It is better to cut smaller sizes later than to cut too much now. You can mark this cut line with a magic marker or you can simply drag a flat-blade screwdriver across the metal so you can see a line in the e-coat. A good solid line is important to use as a guide when you cut the metal with your cutoff tool. Make sure the metal is clear underneath so you do not accidentally cut something you did not intend to. Another tip is to place a strip of masking tape along the line you have drawn to give you a better visual as you cut.
Step 4: Cut Other Sides of Panel
Cut the other two sides of the panel and peel back the panel. The technique is the same to cut the sides of the panel. You just want to be sure not to cut the metal underneath it.
Step 5: Scrape Off Seam Sealer
Use a scraper or utility knife to remove the thick seam sealer that hides the seam between the trunk floorpan and the extension. Once you get under the sealer, you can peel it off.
Step 6: Cut Quarter Panel Seam
Use the cutoff wheel and make a small cut at the metal seam where the extension and floor meet. Use an air saw to cut along that seam. The air saw cut only needs to be about 2 inches long to allow the cutoff tool wheel to smoothly engage the line. If you did not make an initial cut with an air saw, your cutting tool could move back and forth before actually making a cut. That may result in the cut being in the wrong place.
Step 7: Remove Quarter Panel
Cut off the rest of the panel where it meets the rear body panel and wheel-house. Remove the quarter panel and extension. This panel had serious issues and the seam line of the prior patch is now visible.
Step 8: Trim Metal in Quarter Panel Area
With the cutoff wheel trim the rest of the remaining metal edges to reveal the flanges. Remove the spot weld fragments to provide a smooth surface to attach the new trunk extension panel. It may also be necessary to use tin snips, hammer, and chisel to remove the remnants.
Step 9: Remove Excess Sheet Metal
Now that all spot welds and excess metal have been removed, you have a flush surface for attaching the new trunk extension panel. It can be fitted against the edge to verify that the two flanges are flush. Simply using a hammer and dolly on the metal edge to straighten the flange makes the two panels mate together. The rusted panel below the taillights is also being replaced.
This Tech Tip is From the Full Book, TRANS AM & FIREBIRD RESTORATION: 1970-1/2 - 1981. For a comprehensive guide on this entire subject you can visit this link:
LEARN MORE ABOUT THIS BOOK HERE
SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link:
Step 10: Check Fitment of Panel Patch
Check the fitment of the new extension against the floor, wheelhouse, and rear body panel. You must straighten the flanges as necessary to ensure a flush fitment. It is not uncommon for the metal to have distorted somewhat during the remnant removal process. The edges of the new panel need to be checked, because it is common for the edges to distort during manufacturing or shipping.You want to make sure every mating surface matches up squarely for a proper fit. This is accomplished by constantly checking and re-checking every edge of the existing panel and the new panel to make sure the flanges are going to fit flush. When you correct one side, double-check the other side; modifying one side can slightly change the other. This has to be done over and over again until the part fits perfectly. Leaving gaps can, at a minimum, cause leaks or debris to get in or worse, cause an adjacent panel to not fit correctly.
Step 11: Clamp Panel in Place
Test fit the panel and use body clamps to hold it in place. It should fit flush against all flanges. Be sure that all the mating surfaces fit flush against the existing panel as you clamp them into place. This is how the panel will sit after you have welded it. This is not a step to take lightly and should be checked multiple times until you are satisfied with the fitment.
Step 12: Punch Spot Weld Holes
Once you have verified that the panel fitment is good as described previously, remove the panel. Use an air flange/punch tool (available for less than $75) to punch holes in the new panel flanges about 1 inch apart. These holes provide an opening for the spot welds to join to the panel. Take your time and punch the holes in the middle of the flange so the work is clean and professional. This trunk extension is part of the body structure so it should have many spot welds to hold it in place and provide strength.
Step 13: Strip Paint off Panels
Use a wire wheel to clean up the edges of both panels (new and original joining) until they are shiny bright metal. This ensures a clean surface. Use a good-quality weld-through primer, such as 3M Weld-Thru Primer (PN 0511 31-05917). This reduces spatter and distortion caused by excessive heat that occurs during the welding process and replaces certain properties in the metal that are burned off. Spray some weld-through primer on all surfaces that will be welded. A few light coats are sufficient. Let the panel sit 5 minutes between coats and approximately 10 minutes after the final coat.
Step 14: Install Trunk Extension Panel
Clamp the panel into place. Use as many clamps as needed to properly hold the panel in place but still allow enough space to properly weld it. It is critical to fit this panel precisely. The quarter panel attaches to it and any mistake could make the quarter panel look distorted.
Using a good-quality MIG welder perform some test welds on scrap sheet metal to determine the settings to achieve a good weld. Burning a hole in the metal means that the setting is too hot. Lots of spattering can mean that the setting is too cold or that contaminants are on the panel. Every welder requires a different setting depending on its level of power and what material you are welding. Starting the welding at the farthest points and working inward prevents the panel from warping or distorting from heat. This is the same procedure to be used when welding on other panels where you are not plug welding but rather stitch, butt, or tack welding.
Step 16: Inspect Tack Welds
Take a good look at your tackwelds before you continue because you want to be sure the welder settings are correct and you’re not transferring too much heat to the weld area. An excellent plug weld should look like this on both sides.
Step 17: Adjust Patch Panel Radius
A shrinker/stretcher tool lets you easily fabricate gentle radius bends and contours. These tools generally sell for less than $200 at most restoration supply stores. The technique for shrinking and stretching metal takes time and practice. Perform some tests on scrap metal to practice making the metal bend the way you need it to bend. Wear leather gloves at all times. Secure the tool to a workbench. The better the tool is secured, the easier it is to use. Pre-drill and tap two holes into the base; it accepts 3/8-inch bolts. Bend the metal to be formed 90 degrees on a corner or a brake, if you have one. Create a flange that is no longer than 2 inches. Make a template out of cardboard. Trace the outline of the section you want to form. Work the leading edge first. This reduces the resistance and allows for easy and accurate working of the metal.
For best results, place the metal halfway into the jaws. Any metal that rises can be hammered out. Control the amount of pressure you exert on the handle and the number of strokes used while forming the metal. Move the metal back and forth until the desired radius is obtained. The jaws of the tool are ser-rated to bite into the metal. These serrations leave marks, which can easily be smoothed with a grinder or sander. Instructional videos on the Internet can help you gain skill.
Step 18: Form Correct Radius
The replacement quarter patch does not have the slight con-cave roll in the lower portion, as does the stock panel. Although the roll may be slight, you need this roll for an accurate and faithful body profile. Using the shrinker/stretcher technique helps makes the slight bend necessary to achieve the correct body profile.
Step 19: Use Factory Wheel Opening Molding for Reference
It is a good idea to use the factory wheel opening molding (if equipped) as a guide for the proper bend.
Step 20: Create Flange on Quarter Panel: Part 1
You need to create a recessed flange on the quarter panel so the patch panel can overlap the quarter panel and anchor it to the car. An air punch/flange tool is very easy to operate. Simply place the jaws of the tool on the edge of the existing quarter panel until it stops. Then press the button, and the flange is made. The jaws of the tool are fixed so you always get the same size of flange.
Step 21: Create Flange on Quarter Panel: Part 2
Carefully guide the air flange tool across the length of the quarter panel so you create one even flange surface area. Simply keep moving the flange tool over to the next spot after you have made the flange in that area until the entire area you want to flange is completed. You are now ready to final fit the patch panel.
Step 22: Cut Patch Panel
In this photo, our veteran body technician trims the panel on a parts cart. I recommend using a workbench that affords you plenty of room. Make sure the patch panel is clamped or firmly held down on the bench. Position yourself so you have a clear sight line to the tape because you want the cut to be as straight as possible. Start from one end and methodically move the rotary across the trim panel until the cut is complete. The procedure is described in Step 3.
Step 23: Prime Patch Panel
Treat the panel with a weld-through primer. The 3M product’s quality is second to none and I always get consistent results. Place the panel over some newspaper or a spray cloth and evenly coat all the edges of the patch panel that will be welded. I typically apply two coats for thorough coverage. After the primer has been applied, use an air punch/flange tool to place spot weld holes 1 to 1.5 inches away from the edge and spaced 1 to 1.5 inches apart. These holes align with the flange area on the quarter panel and the spot welds hold the panel in place.
Step 24: Tack Weld Patch Panel
Properly fit the patch panel in place using body clamps. Drill holes into the adjoining panel for spot welds Tack weld the panel starting at the corners. This is the same procedure used on fenders.
Rear Body Panel Sectioning
You need to section the rear body panel if the lower half has been previously rotted and poorly repaired. The upper half may be in good condition and structurally sound. Remember, you do not have to replace an entire panel just because you purchased it. This is especially true with structural panels. On this project, I was able to remove the lower section below the frame rail attachment point and leave the body structurally intact. This makes for a better repair.
Sometimes the entire panel may need replacement. Every car rusts differently depending on its care (or lack of care) and the environments to which it has been exposed over its lifetime.
I will section the panel just below the spot welds where the rear body panel ties into the trunk floor. This process is not exceptionally difficult, but it requires exact measurements and concentration.
You want to ensure that the part of the panel that remains on the car is solid. You should cut at least 1/2 to 1 inch beyond the edge of the corroded or rusted metal, so the panel serves as a solid foundation for the patch panel. Multiple measurements are critical so a proper cut is made. In the body Industry, this is called sectioning, and it means you are only replacing a portion of the panel and not the entire panel.
When trimming a wide panel, leave a strip of metal toward the center to help assist with placing the panel. Once you have the panel where you want it, use a cutting wheel to lightly cut a groove into the new panel and existing panel to create alignment marks. This allows you to take the panel on and off for final trim but still line it up properly.
Tail Panel Installation
Step 1: Inspect Trunk and Valance Area
The lower portion of a rear body panel is a common area for Firebirds to rust. The 1974 and later Firebirds tend to have more rust in this area because the sheet metal is hidden behind the rear bumper cover and moisture gets trapped behind the bumper cover. Often that area is not cleaned because it’s not visible.
Step 2: Determine Cut Line on Valance
This cut panel reveals prior body filler and rust. After determining where the solid metal starts, use a cutoff wheel to cut along your marked line to properly section the panel. You need to find clean, non-corroded metal so you can cut at least 1.5 inches into that solid metal surface.
Step 3: Remove Rust from Valance
It’s important to remove all the rusted sheet metal from an area; once metal has started rusting it doesn’t stop until it’s cut out and replaced with fresh sheet metal. You can use a cold chisel or screwdriver to knock off the rusted metal; a chisel often works the best. A hammer and chisel are typically required for tougher spots.
Step 4: Inspect New Sheet-Metal Panel
Here is the new replacement panel prior to being sectioned. It is important to measure multiple times before cutting the replacement panel. Several suppliers offer this rear body panel, including Tamraz Parts Warehouse (I bought one for $288, including shipping). If you trim the panel a bit longer it can incrementally be trimmed until a perfect fit is made rather than trying to add metal to fill the gaps.
Step 5: Apply Rust Neutralizer
Once you have removed the panel, cleanup is needed. Use a rust neutralizer such as Mar-Hyde One-Step (PN 3509). It converts the rust into a black primer sealer.
Step 6: Neutralize Rust
Apply rust neutralizer to the exposed metal on the original side and the back side of the new panel to help minimize corrosion.
Step 7: Punch Spot Weld Holes in Rear Valance
Use an air punch tool for adding holes on the bottom and sides approximately 1 to 1.5 inches apart. Be sure to place the holes in the center of the flange for a neat and clean appearance but also so the panel has the best support and strength when attached. Find a large clean area of your shop to spray down the valance with weld-through primer. Apply the anti-heat compound to the existing part of the taillight panel (as you did when repairing fenders). Using the anti-heat compound reduces the possibility of warping the tail panel while welding.
Step 8: Clamp Patch Panel in Place
Start clamping the panel in place and trim the edges as needed to make them fit as close to the original panel as possible. Make sure that the new valance is correctly aligned with the existing panel. Once it’s tack welded in place, you would have to cut off or grind down the tack welds to realign it. Again, place the spot weld punch holes 1 to 1.5 inches apart. Use the body clamps as needed to hold the panel in place but allow enough room for welding.
Step 9: Butt Weld Seams
Align the new lower body panel with the existing upper body panel. Tack weld a couple of corners along with the existing ear. Press along the line where the new panel meets the old to make sure there is no overlap. Here, I butt weld the two panels together. You want the seam to fit as flush as possible so you have less metal work to do and use less body filler later. You cannot plug weld the panel because there isn’t a flange. You need to trim the panel in the middle. Make sure the MIG welder is set at the proper amp setting and the correct wire is being used. Make the actual welds start at the farthest point and work inward. Once enough of the panel has been welded the ear can be simply cut off.
Step 10: Tack Weld Patch Panel: Part 1
Tack weld on the outside of the panel and work your way to the center. Keep the body clamps in place until you have spot welded in the center of the panel. You do not want the panel to shift during this process. Place about a dozen spot welds at the outside of the panel on each side.
Step 11: Tack Weld Patch Panel
Remove the center ear that was used to anchor the lower panel to the upper panel. Place spot welds every 8 inches along the seam between the upper and lower valance panels (the panel is now securely welded in place). Remove the body clamps. When all the spot welds have been placed along the panel seam, start stitch welding between those seams. It's like connect the dots.
This thin-gauge sheet metal can withstand a moderate amount of heat before it starts warping, and warpage must be avoided. Lay down a bead of weld between two spot welds and them move to the opposite end of the panel so you are spreading the heat. Apply air to the area of the panel that has been stitch welded and let it cool for a few minutes. This is the best way to avoiding warping the panels.
Step 12: Smooth out the welds
After the panel has cooled, grind the welds smooth to finalize the metal work. A coarse 36-grit grinding disc on a DA sander is sufficient to remove the weld slag.
Written by Melvin Benzaquen and Posted with Permission of CarTechBooks
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