Whether you prefer paint, powdercoating, or just good old chrome, those two hulks of press-formed steel hanging off the front and rear of your car often need some attention. Bumpers are there for one real reason—to protect the car in low-speed accidents, but they can also bring style and flare to your car's body in a unique way. When building a custom ride, the bumpers can serve as an excellent opportunity to show off your design skills, if you have the nerve.
The main issue with modifying bumpers is that chroming requires a perfect surface. There cannot be any imperfections in the base metal, or it will show up like a glaring zit on your nose on prom night. The key to tricking out a bumper is the processes used. Welding is easy enough, but unless you are a TIG master, MIG welding is likely the method used for most mods. If you plan on painting the bumpers, then a little body filler finishes the task, but what if you want to powdercoat or chrome your custom bumpers? In that case, you will need to take a page from the days before plastic body filler—that's right, lead body solder.
Modifying bumpers requires a few steps that you might miss if you didn't realize it was necessary. Before doing any actual work on the bumpers, they need to be stripped. The top layer, Chromium, is actually very thin and clear. This is the protective coating for the base layer of nickel. Some bumpers have a third layer of copper, but not always. In order to properly weld on the bumpers, the chrome coatings must be stripped away completely. If you have access to a chrome shop, they can chemically strip your bumpers using the reverse process for chroming, which is electroplating. Most of us do not have such access, so the best method is a high-speed grinder and some elbow grease. A paint stripper or flap wheel works best here, as you only want to remove the chrome layers, not gouge the steel. You don't have to strip the entire bumper, only the areas that will be modified.
Once the chrome is gone, the real work begins. The most common bumper mod is shaving the bolt heads. The trick is that you still have to mount it back to the car. You could weld the brackets directly to the bumper, but that eliminates the ability to adjust the bumpers later. The best bet is to weld the bolts in place. Using a carriage bolt, the head is removed, leaving the square base that fits perfectly in the original hole. In order to keep the bolts in place, it is a good idea to bolt them to the brackets and clamp the brackets to the bumper. Once the bolts are welded into place, the remaining nub on the outer surface gets ground off, leaving a smooth, bolt-free look.
Even though a good weld job can often be ground smooth, there are still imperfections that won't disappear under chrome. This requires some finish work using lead body solder. There are two types of body solder: lead and lead-free. Lead-free solder is made of an antimony alloy, which is easier to work with, has a longer plastic window, and is much safer than pure lead. We ordered our lead-free components from Eastwood, who has everything you need to make it happen.
1. The project began with a set of driver-quality bumpers for our ’69 Road Runner. This car needed something extra, so the bolts were shaved and all the unnecessary openings filled with 1/8-inch plate. This piece was cut with a plasma torch and ground to fit with a grinder before being bent.
2.-3. The area around the marker light and license plate holes were prepped with a grinder before a series of welds were laid down to secure the panel. Using stitch welds as shown will reduce the warping of the bumper. Filling the tag location in the center was significantly more challenging. Four pieces were cut to fit and then stitched into place with the exception of the bottom edge.
4. Using an oxy-acetylene torch, the lower section was heated to cherry red and tapped into shape to re-create the roll of the original bumper.
5.-6. The mounting holes were the simplest mod. The heads were cut away from Grade 8 carriage bolts and tacked into position using the brackets to secure the bolts in the correct place. Next, the brackets were removed and the bolts welded from behind. It is a good idea to stack a few nuts on the bolts to keep slag off the threads.