Metal Replacement Pt 1 - Replacing the trunk floor
Turning Worthless Metal Into A Valuable Asset
By Rob Halas
What we are going to show you over the next year or so is how you can take a rusty and seemingly worthless hulk and change it into a valuable asset with a little time and effort, (well, depending on the condition of what you start with, it could be a lot of time and effort, but as long as you are having fun though, right?) The main thing is to be patient and take your time; the end result will be well worth it!
The procedures we describe here can be used on almost any vehicle, but especially apply to older iron. There are other ways that the same things can be accomplished, but the methods we use are what we feel are the best and easiest using common tools, and they have worked for us. Of course, some equipment is necessary, like a welder, grinder, drill, etc.
The intent of this series of articles is to show how to replace rusty or damaged sheet metal with fresh new steel. As we are going to completely restore/modify this particular Barracuda, we elected to totally strip and media-blast the shell. We even roughly cut the quarter panels off for easier access. This does make it nicer to work on, but is not absolutely necessary, especially if you intend to replace only the affected part and/or if the rest of the car is good.
The guidelines that follow assume that all of the surrounding bolt-on parts are removed.
Removing the old floor
The first area we will tackle is the trunk floor, a common area for rust on many older cars, especially E-body Mopars. We used a two-piece floor as the tail panel is to remain in place; if the tail panel is going to be removed, a one-piece floor can be used. They are of a little better quality and make for a nicer overall job if you do go that route.
After making sure that the tail panel and frame rails are straight and true, and the car is level, the first step is to carefully cut the floor out in sections. Use an angle grinder with a zip-cutting wheel or a plasma cutter and make sure you inspect underneath so that you do not cut into the frame rails or any area that is not being repaired or replaced. Cut close to the edges where metal is overlapped/joined by the factory, then drill out the spot welds. Sometimes they can be tough to drill and even though you may seem to have drilled the weld out completely, the metal may still be stuck together. The remaining bits can be pried, pulled, bent and twisted until they come free. However, be careful not to bend and distort the remaining metal that you are going to attach to.
A few useful tips. We used new gas tank braces and did not try and save the old ones. Mark and measure the placement of these and any other tabs or brackets that you will be re-using or replacing. You can also use another car as a guide if you elect to, or if you miss something.
After metal is removed
After all the old metal is removed, grind any spot welds down and make sure the frame rail flanges are straight and flat, as well as the front, rear and side portions that the floor will be attached to. Sometimes it is necessary to make up small patches if those areas have rust holes; form, fit and weld those before installing the new floor.
Now, test fit the new floor pieces; sometimes trimming is needed, but don’t get too carried away yet. If you are fitting the parts between the trunk extensions, use them as the baseline and use vice grips to hold them in place. Check and see how the overlap is in the centre, as you may have to trim to get them to fit properly together. By now, you should have an idea how everything fits, so now use a few self-drilling/tapping sheet metal screws to hold everything in place; as the floor forms to the frame rails, you may have to adjust the surrounding areas, so don’t use too many yet. If the edges look good, start installing the screws approximately every three inches along all sides, the centre, and the frame rails. The screws do two things - they locate and hold the sheet metal tight and they provide a hole to plug weld through later. (Note: with the parts we used, the rearward edges were way off, so we used the front edges and sides to determine the best fit.)
Metal screws in place.
Now that the floor is located and secured in place, remove all the screws and parts and do any final trimming. Now drill half of the holes oversize; we find that 5/16-inch is about the best for plug welding. What I mean by half is, only drill the holes that you will be welding through and not the matching part you will be welding to; for instance, drill the trunk floor holes where it meets the frame rails, but not the rails themselves. You can drill oversize either the new or existing part, but drill the one that is easiest to get to with a welder.
With everything open, now is the time to brush or spray rust stopper such as Rust Mort or POR 15 into the frame rails and let dry.
Welding the floor in place.
Now, re-install the floor using the screws again, then remove one screw at a time, or every third or fourth screw, and start plug welding! After welding, continue to remove screws until everything is welded; you may also elect to weld the edges of the new and existing metal together. We also use primer on any bare steel that will be hidden from being painted later, way over and above what the factory did. Now you can carefully grind the welds to prepare for finishing and painting.
Next time, we will be on to the passenger floor area!
Rob Halas is the owner of WeldTech Industries located in Surrey, B.C. The company specializes in installing sheet metal on your classic car. Check out their website at www.weldtech.ca
Related Posts
© Copyright RPM Media Inc. All Rights Reserved. Site Design by JC Design