[pontiac1981]

I have a 81 trans am that i need to replace the floor pan on the drivers side, i've never done this before and i would appreciate any help on cutting out the old and installing the new one. i bought a new floor pan that measures around 49x21, i bought a rand welder and welding rods. i'm thinking that i would lay the new pan down over the old and trace it then cut about a 1/2 inch on the inside of the line, does that sound about right? and i was wondering what needs to be done with the bolt holes for the seat brackets. and what type of tool would i use to cut out the old pan? thanks for any help.

[mikeb]

There are a couple of crossmembers under the floorpan that the seat bolts to - DO NOT cut these crossmembers out when you remove the old floorpan. As far as the rest - I don't know.

[pontiac1981]

thanks mikeb, would you know how these crossmembers are connected to the floor pan? are they spot welded?

[Smasher]

the braces are spot-welded to the floor. As far as tracing out the new floor and leaving a half-inch overlap, that sounds good. If you have air, I would use a cutoff wheel to get the old floor out. If not, I suppose a sawzall or electric grinder would do the trick, but be careful! I'm not sure how bad your floor is, but remember, you don't need to use the whole replacement floor. The more you can leave original, (as long as it's good) the better. Good luck!

[1badkiller]

Take some blue painters tape and put one little piece on the tranny tunnel as far up as you can go, and still be in line with the door sill, then put a piece on the door sill even with the one on the tranny tunnel....then go back 8-10 inches and do it again on both the tranny tunnel and door sill....do this all the way to the back of the door sill.....Now take a sheet of paper and make a little drawing of the floor pan, noting how many pieces of tape there are and where they are located....Now take a straight edge or a 2x4 and lay it across from one tape to the other, and measure down from the bottom of the board or straight edge till you tough the floor pan...do this on the inside of the pan and the outside for each piece of tape, then record your measurements.....now once you remove the pan and go to weld it back in your seats will be back where they originally were and your head wont hit the roof, or you wont look like granny trying to see over the steering wheel.....I did this in my stang, and it worked PERFECT...i have pictures if your confused.....you can use a saw zaw or an air cutter or what ever you want, but do like you said put the pan in then cut 1/2" higher.
and i would use a wire feed welder, the pans are generally pretty thin, and a stick welder will be tough to use, especially if you are not in good practice when you weld upside down...Mig is much easier.
Mike

[Grand73Am]

I agree that a stick welder will be very difficult. I don't think it's going to work with thin sheet metal like that. A MIG is the way to go.

Also when cutting out the floor, 1/2" to the inside of the line is not enough. I suggest leaving at least 2" inside the line to begin with. Once the old floor metal is cut away, your new pan will fit down deeper than before and not reach as far as it did when you drew the line. So, if you only leave 1/2", the new metal won't reach the old metal and leave gaps, which would be a big problem. So, by leaving more metal, you can always trim it back some more as you get a better idea of what's needed.

For cutting tools, a cutting wheel on an air powered die grinder will be very useful. Here's the type of cutting wheels to use. The thin 1/32" ones like these cut faster and easier: http://www.northerntool.com/shop/too...5521_200305521

Also, an air powered recipricating body saw speeds the cutting up after you get the hole started with the cutting wheel, like this one: http://www.northerntool.com/shop/too...ct_22114_22114

And an air chisel helps to separate the old floor from the body brace welds, and cutting difficult places to get to: http://www.northerntool.com/shop/too...2899_200342899

And finally, I suggest getting a pair of snips like these: http://www.northerntool.com/shop/too...4072_200384072

[Ollie]

Invest in a dozen Clecos.
Clecos are used to temporally hold two pieces of sheet metal together when working on them. Go to eBay and search key word Clecos.

[Grand73Am]

That's good advice about fastening the pans down in position before welding. Rather than Clecos, I screw the pans down by drilingl 3/16" holes and screwing them down with 1/4" sheet metal screws with hex heads from a hardware store. Then remove them as you weld the floor in and plug weld the holes. Use an air ratchet to screw them in and out.

[pontiac1981]

Thanks everyone for the advice and help some of the advice is a bit confusing but i'll figure this job out.