Floor Pan Replacement

Q: Floor Pan Replacement

I am about ready to replace the floor pans in my Firebird. Anything special I need to do or suggestions for completing this task.

A: I’m no expert, but I did replace the floor pans on my 1968 firebird. Some of the things I learned are:

• Do one side at a time to keep the body straight. If you have a convertible, weld in some temporary supports from the dash to the rear seat. (Angle iron or square tubing)

• Cut around the forward body mount brace and use that to locate that corner of the floor.

• Cut around the extra bracing for the leaf spring front mount, and use that to locate the back of the floor.

• The seat support has about a million spot welds, and you have to take that off to get to some of the spot welds for the body mount which is under it.

• Measure the distance from the old floor to the top of the door sill or to the bottom of the rocker panel before cutting out the floor and use that dimension to locate the outboard side of the new one.

• There are a couple of factory holes in the transmission hump which can be used as reference points to locate that edge. I left 3-4″ overlap so I could move the floor pan around, and to maintain the strength of the transmission hump without the old floor.

• Set the new floor on top of the old one and mark the edge with a soapstone, then cut 3-4″ below the line, going around the aforementioned items.

• It is easy for the floor to twist and get away from being level, so check that often while welding.

• Plus the basics: tack weld in various areas, and move around a lot, so as not to warp the floor. Seal the seams when you are done with seam sealer, available from various suppliers.

Again, I am no expert, and you may get better advice on this board to be 100% factory correct.

A: I’m not an expert but I’ve done a couple of 1969 floor pans… One coupe and one convertible. First thing you need to no is that the convertible will be much more difficult than the coupe. When I did mine, I left the belly brace ( the brace that is underneath the car) in place. You may also want to support the car in to keep it from buckling in the middle. A brace at the top of the door between the door jam on each side is best. Do one side at a time to keep as much support a possible. After this I used these procedures:

• TAKE NOTE OF THE LOCATION OF THE GAS AND BRAKE LINES IF THIS ISN’T A FRAME OFF RESTORATION.

• prime and paint new pan.

• removed the seat pedestal.

• removed the rear seat floor brace (the angle piece connecting the tunnel to the rear jam).

• remove bottom of old floor pan and clean up belly brace (take note of the different support pieces that are welded to the original pan. remove as much old metal as the pan will cover but leave these supports in place).

• set new pan in place and scribe a line around the top of the pan onto the old sheet metal (make sure it sits tight on belly brace, use screws if necessary).

• trim excess metal approx one inch below line.

• re-install new pan and re-check scribe line. (make adjustments as needed).

• while pan is in place, mark seat belt location, rear sub-frame attachment point and the different brace locations from underneath the car.

• once your satisfied w/ fit, trim to 1/2″ of scribe line

• cut holes for seat belt and frame attach point.

• I drill holes in the pan to allow me to spot weld through the pan to the different brackets located on the bottom of the car.

• install pan and weld (tack weld all the way around about 4″ apart then tack in between first welds until welds are 1 to 2 inches apart then weld solid).

• re-install rear brace.

• reinstall seat pedestal.

• repeat for other side.

• Be sure to caulk area between the new pan and the inner rocker panel.

• TAKE YOUR TIME.

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