At first glance, this trunk doesn't look all that bad-just a couple of small holes. For those of you who are new to rust repair, what you can see is just the tip of the iceberg. Sheetmetal in this condition is thinner than you think, and there is likely a lot more damage hidden from sight.At first glance, this trunk doesn't look all that bad-just a couple of small holes. For th There are two reasons to use a factory replacement part from a donor car instead of a reproduction. The first is if you are building a car that has little or no aftermarket support. The second is if you are an owner of a '69 1/2 440 Six Pack Super Bee (code A12) and you want to claim that it contains all factory stuff. Muscle Car Restorations (MCR) in Chippewa Falls, Wisconsin, certainly had to learn to deal with the dwindling supply of original muscle over the last two decades, and anxious owners worried about their investments. It's actually common now to replace the passenger and trunk floors in most of the cars the company restores. We're going to show you the correct procedure for a trunk floor installation on this Mopar B-Body, including having to deal with the annoying overlap you'll find on lesser-quality restorations. The methods used can be adapted to the replacement of just about any piece of sheetmetal on the car. Try it. A few easy taps with a pick hammer show how bad it really is. Don't mess around with rust, especially on a keeper like this. Treat it like cancer and cut it all away.A few easy taps with a pick hammer show how bad it really is. Don't mess around with rust, The replacement floor is from another B-Body. The ideal replacement floorpan should be cut along the trunk extensions and up to the flat area between the wheeltubs. Someone cut this one a little bit short. Get as much trunk floor from the donor as you can.The replacement floor is from another B-Body. The ideal replacement floorpan should be cut Chris at MCR drilled out the two rows of spot welds that secure the trunk brace to the floor using a spot-weld cutter. The guys at MCR prefer the Blair 3/8-inch Rotabroach cutter and a Century 1/8-inch double-ended drill bit for this job.Chris at MCR drilled out the two rows of spot welds that secure the trunk brace to the flo Chris placed the replacement floor in the trunk and drew an outline around the donor floor. Removing the fuel tank brackets at this point will make the job easier.Chris placed the replacement floor in the trunk and drew an outline around the donor floor Using a good cutoff wheel, Chris cut through both pieces in the center of the overlap, peeled back the excess, and placed a tack weld about every inch or so. He aligned the gap by prying up on the floor with a small screwdriver to be sure both parts were perfectly even before placing each weld. Since the new trunk will drop down into place, he made sure to keep the cutoff wheel vertical so the gap didn't get too large. In this case, it was especially important along the front edge where the panel slopes upward. This is why you'll want to get a panel that's cut all the way out to the trunk extensions. Remember where that center brace is located so you don't hack through it.Using a good cutoff wheel, Chris cut through both pieces in the center of the overlap, pee Don't be surprised if you need to use a chisel to pop loose a few of the spot welds to remove the last piece of floor from the center brace. You will also need to grind off the remains of the spot welds.Don't be surprised if you need to use a chisel to pop loose a few of the spot welds to rem TECH NOTES DESCRIPTION PN SOURCE PRICE Blair Rotabroach 3/8-inch cutter 11108-3 Blair $21.88/three pack Replacement floor panel N/A DVAP Call Arbor for cutter 11122 SJ Discount Tools 13.92 3-inch 36-grit Roloc disc 22393 3M 47.00/box of 50 Roloc disc holder 05540 3M 18.17 Weld-grinding wheel 051131-01991 3M 33.65/5 Scotch-Brite Clean and Strip disc 6-inch x 1/2-inch extra coarse, black 61500120722 3M 12.47 A 3M Clean and Strip Disc works great to clean up the inside of the brace. This car will eventually be E-coated, but 3M Weld-Through Primer or a product such as POR-15 can be used to protect this inside surface.A 3M Clean and Strip Disc works great to clean up the inside of the brace. This car will e The torched edge on the replacement floor from the junkyard needs to be trimmed with a cutoff wheel. Chris scrawled a guideline using a straightedge, being sure to use the business end of the Sharpie.The torched edge on the replacement floor from the junkyard needs to be trimmed with a cut Chris replaced the floor and again traced around the outside so he could trim the edges of the original floor and leave a slight overlap. He reinstalled the replacement floor and tack-welded it in place so it stayed put while we made the final cuts.Chris replaced the floor and again traced around the outside so he could trim the edges of Using a good cutoff wheel, Chris cut through both pieces in the center of the overlap, peeled back the excess, and placed a tack weld about every inch or so. He aligned the gap by prying up on the floor with a small screwdriver to be sure both parts were perfectly even before placing each weld. Since the new trunk will drop down into place, he made sure to keep the cutoff wheel vertical so the gap didn't get too large. In this case, it was especially important along the front edge where the panel slopes upward. This is why you'll want to get a panel that's cut all the way out to the trunk extensions. Remember where that center brace is located so you don't hack through it.Using a good cutoff wheel, Chris cut through both pieces in the center of the overlap, pee Once the replacement panel was tack-welded in place, Chris went around again and placed another tack weld between each of the first round of welds. To avoid any heat buildup, he quenched the area with compressed air and moved around.Once the replacement panel was tack-welded in place, Chris went around again and placed an When the second round was done, Chris did it again. At this point, the welds should all be about a quarter of an inch apart and ready for the gaps to be filled with a few quick tack welds. Don't run a short bead here-this is not stitch welding. Instead, tack-weld the tack welds together. While a trunk floor is not as sensitive to heat warping as a quarter-panel, the goal is still to keep body filler to an absolute minimum so the seam becomes invisible.When the second round was done, Chris did it again. At this point, the welds should all be Chris ground off the excess bead with a 3M weld-grinding wheel leaving a very slight crown to avoid touching the original material. If you spot any pinholes along the way, go ahead and place another tack weld to fill them in.Chris ground off the excess bead with a 3M weld-grinding wheel leaving a very slight crown Chris ground the area with a 3-inch 36-grit weld-grinding disc and an 80-grit disc on a DA to get the area ready for a skim coat of body filler.Chris ground the area with a 3-inch 36-grit weld-grinding disc and an 80-grit disc on a DA The final job was to hold the floor tight to the brace and plug-weld the two together. Chris finished the welds just like the seams to make the car ready for filler and sealer.The final job was to hold the floor tight to the brace and plug-weld the two together. Chr SOURCES 3M Corporate Headquarters 3M Center St. Paul MN 55144 888-364-3577 www.3m.com Century Drill and Tool Co. Green Bay WI 920-339-8700 www.centurydrill.com Muscle Car Restorations 11371 20th Ave. Chippewa Falls WI 54729 715-834-2223 www.musclecarrestorations.com Desert Valley Auto Parts 23811 N. 7th Avenue Phoenix AZ 85085 623-780-8024 www.dvap.com Blair Equipment Company P.O. Box 2005 Flint MI 48501 810-635-7111 www.blairequipment.com By Mark Ehlen Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
