Chevy Impala Front Floorpan Replacement - Flooring It

Whenever any cutting or welding is contemplated on a floorpan, the first thing to check is where the fuel line runs. On the Impala it ran along the inside of the passenger side chassis 'rail, very close to where we'd be cutting and welding.

Unhooked from the factory clips, the fuel line was dropped a couple inches until it rested on the trans crossmember. Before we started cutting, it was inspected for leaks, then when deemed safe, wrapped in a fire retardant blanket normally used to protect paint, glass, or interior trim from weld spatter or grinder sparks.

With safety issues taken care of, work could commence. The replacement floorpan from CARS is a nice piece, and fits well. It appears to be designed as an overlay panel, whereby it's simply welded over the old floorpan, though the original could be removed to within an inch or so of the replacement's edge, leaving a lip to overlap and weld.

We prefer to make repairs as invisible as possible, even on a floorpan. Besides, there was no need to replace such a large area and create unnecessary work by welding up the sides of the trans tunnel and toeboards when the rusted area was much smaller. Therefore, we marked the new panel to be trimmed.

Ignoring the obvious lack of gloves or safety guard (this was for "photographic purposes" only, honest!), the CARS panel was cut to size using a 4-inch grinder and cut-off wheel from Harbor Freight.

With the trimmed panel laid in place, its perimeter was marked using a silver Sharpie, which would provide my cut line to remove the original floor section. Of note here is that the front edge of the trimmed panel is actually on a factory lap joint, so this will appear stock once we're done. Cutting across any swage lines was purposely avoided for ease of cleanup after welding.

An air saw was used to trim the old floorpan away, partly because it produces no sparks (given that this is a regularly used car with oil and grease on the underside, and the proximity of the fuel line) and partly because it's often quicker than using a cut-off wheel.

We removed the old floor section by cutting an inch or so behind the lap joint at the base of the toeboard, then used the spot-weld drill to remove the welds. A chisel made light work of any remaining small welded sections. Note how the underlying sheetmetal is not damaged by the drill, and the fuel line is wrapped in a fire-retardant blanket.

With the old rusted floor section removed, the old paint was removed from where we'd be welding using a 36-grit pad on an air sander. The same tool was used to trim the edges to allow the replacement panel to fit perfectly.