Steppin' Out

You never get a second chance to make a first impression. The same is true of custom-crafted pickups, especially when you open the door to let a passenger climb in. Will that guest be greeted by nice carpet and custom paint, or frayed fabric and rust holes?

On '55-59 Chevy pickups, passengers enter the cab using a wide doorsill, one that can be likened to a step or running board that sits inside the doors. As you'd expect, these sills take a beating over the years and are often riddled with dents and rust--not the sort of qualities that make good first impressions. Fortunately, replacement panels are readily available and not too difficult to install. Over the next few pages we'll be showing you the highlights of such a procedure using a pair of replacement panels from Brothers truck parts.

Our patient for this operation is Paul Darden's '59 Chevy cab, which you may remember from last month's "Perfect Patch" story chronicling cab corner replacement. Once again our surgeon is Bryan Fuller, one of the metalworking masters at GMT Quality Metalwork & Fabrication in

Huntington Beach, California. Compared to last month's cab corner surgery, the doorsill replacement is a little more cut-and-dried since the panels fit along factory seams. In other words, you don't have to figure out where to cut and splice because the seams are already there to work with. That doesn't mean that the procedure is a total cakewalk, though, because drilling out the spot welds along these seams can be a time-consuming chore in itself. Just like with anything else, patience and perseverance will pay off if you take things one step at a time.

As we mentioned last month, Bryan's first task before replacing anything on the truck was to make sure the cab was square and the doors fit properly. This meant adjusting hinges and doing some "convincing" on the door openings using a Porta-Power. "The cab has a lot of its strength in the rocker panels [which are part of the sills], so it's a good idea to have the doors fitted and on while doing this operation," Bryan says. "That way you can check the door gap on the bottom of the door as you're installing the rocker. You wouldn't want to get it welded in, hang the door back on and find it doesn't shut because you didn't double check."

With everything square and the cab thoroughly braced, Bryan made his rough cuts, slicing out most of the old sills with a plasma cutter. Getting the bulk of the old metal out of the way made it easier to concentrate on the next chore--drilling out the spot welds.

When cars and trucks are welded together on an assembly line, spot welds are the most common means of securing panels to each another. It's called resistance welding--where two (or more) panels are sandwiched between electrodes and zapped by current until the metal is molten and becomes one. When one of those panels needs to be replaced, the spot welds must be drilled out so the parts can be separated. Most auto body suppliers carry special bits designed for drilling spot welds that make the task a lot easier, although panels will often need some additional convincing to come apart after sticking together for so many years.

Once the old sills are out you'll need to make any necessary repairs to the flanges (fixing rust holes, hammering the metal straight, etc.) before trial fitting and installing the replacement panels. From the factory the L-shaped sill panels sit on top of the lower flanges and vertical flanges, and slip behind the upper flanges where they meet the floor. Bryan did the same with the replacement panels, although he opted to position them on the outside of the upper flanges so the welds would be hidden. He held the sills in place using Cleco-style clamps, then plug-welded the new panels using the holes from the spot welds.

Plug welding the panels may seem pretty self explanatory, but Bryan had a few words of advice on this matter. "When welding spot welds, most people don't turn the heat up enough," he says. "Do some test pieces with the material size and some 5/16-inch holes to test. If done right, the welds should turn out almost flat, requiring little grinding."

As we mentioned before, the rocker panels on these trucks are integral parts of the doorsills. They tie into the cab corners with a seam at the rear of door, where the rockers overlap flanges on the cab corners. Since the cab corners on this truck were being replaced too, all of the old stuff was just cut away and the junction recreated with the new parts (the seam was welded smooth for a cleaner appearance). If your cab corners don't need replacing you have a couple of options. You can drill the spot welds of the seam, separate the panels, then weld them back together like original. Or you can cut the rocker ahead of the seam, trim the replacement panel accordingly, butt weld the old metal to the new, then grind and finish this new seam until it disappears. As we showed you last month, Bryan also welded a piece of 1 1/4-inch tubing along the back side of the rocker panel, adding some extra strength to this damage-prone area. This bracing should also prevent excessive flexing, which Bryan wanted to minimize after welding the rocker panel seam.

The accompanying photos highlight the basics of Bryan's doorsill surgery. Check 'em out and see what it takes to get an old Chevy steppin' out in style.

Off with the old and on with...        read full caption Off with the old and on with the new. Though the old doorsill on this '59 Chevy looks fairly decent in this photo, GMT's Bryan Fuller felt it would be just as well to replace the whole panel rather than patch and fix the multiple trouble spots. The replacement panels are from Brothers truck parts.	Bryan used a plasma cutter...        read full caption Bryan used a plasma cutter to quickly get the bulk of the old metal out of the way. This isn't totally necessary, but makes things a little easier when you start separating the panels at the flanges.	To make the repair as clean...        read full caption To make the repair as clean as a factory installation, Bryan separates the panels at the seams. This process begins by locating all the spot welds and drilling pilot holes with a small drill bit.
Drilling spot welds is made...        read full caption Drilling spot welds is made easier and cleaner if you use a spot weld drilling bit like this. These are available through auto body suppliers or specialty outlets like The Eastwood Company.	The bit lets you drill out...        read full caption The bit lets you drill out the spot weld without opening up a large hole in both panels.	It's probably unfair for us...        read full caption It's probably unfair for us to jump ahead to this photo because it makes the process of panel separation look so easy. Nevertheless, this is what you're aiming for--bare flanges ready to accept new panels. A little prying persuasion is generally necessary to separate the panels after the spot welds are drilled out, so the flanges will typically have to be straightened out with a hammer and dolly. We should also note that the panel is not just attached around the perimeter--notice the support brace in the center.
Bryan uses a weld-through...        read full caption Bryan uses a weld-through primer (phosphate-rich) to cover the bare metal flanges before trial fitting the new panels. The primer will help prevent corrosion within the seam once the panels are welded together.	Next the new door sill panel...        read full caption Next the new door sill panel is trial fit in place. Note that Bryan also has the replacement cab corner mocked in place at this point. Since the two panels join together, it only makes sense to make sure they fit together properly before beginning to weld either one.	With proper fit achieved,...        read full caption With proper fit achieved, Bryan holds the new sill panels in place using Cleco-style clamps. You can see here that Bryan strayed slightly from OEM specs by placing the new sill panels on the outside of the upper flanges, rather than slipping them behind the flanges. This will simplify the repair and make the finished product tidier by keeping all the welds on the back of the panels.
A look at the rear of this...        read full caption A look at the rear of this sill shows how it fits together with the new cab corner. Note how the rocker panel portion of the sill panel overlaps the cab corner where they join. This seam was spot-welded from the factory, but Bryan eventually welded the seam shut and metalfinished it for a cleaner appearance.	Now it's finally time to begin...        read full caption Now it's finally time to begin welding. Bryan uses a TIG for most of his work, although a MIG machine would work fine for a repair like this. As mentioned before, the sill panels were primarily plug welded on the back side using the drilled-out spot weld holes, but Bryan also had to fill a few Cleco holes on the top sides. (All seams were coated with seam sealer on the back.) Note that this cab corner has been tack welded in place at this point, and the seam between it and the sill panel is already welded and ground smooth.	A view from underneath and...        read full caption A view from underneath and a couple from up top show the repairs after welding and finishing. Pretty slick, huh? The panels look as good as new originals -- even better because most of the welding was done on the back of the panels, hiding the welds and eliminating a lot of finish work. Spray on a little primer and they will be ready for prep and paint.