Floor Pan replacement

[allstar12316]

On my 66 its time to start cutting out the floors and do some sheet metal work! It is better to drill out spot welds on the floor take out old floor, frop in new floor and fill in the spot welds? then i obviously need to seam seal but is that the best way? or do i make a bead of the weld around the edge of the pans?

[66DavesGT]

Drill out the spot welds to remove the old pan. Fit the new pan (one piece pan highly recomended) and drill out holes in the pan to plug weld to the frame rails, crossmember, etc. If its a coupe or fastback the sides of the pan sit against the inside of the rocker. If it's a convertible you need to drill holes along the sides of the pan and plugweld to the underside of the inner rocker.

[manley]

I used plug/spot welds. Seam welding thin sheetmetal never seems to look very good and I've heard the spot weld method is stronger.

[Fstbk]

Just pre-punch holes in your new floor pan and rosette weld the new one in place. Use a weld through primer or paint on the edges before you weld to reduce future rust. No need to make a bead weld when it's so easy to replicate the factory look.

Then use epoxy primer over all of the joint areas, let that dry and then sea, seal, now you are ready to prime the entire pan inside and out.


I prefer the SPI red oxide myself, you won't need any additional goo or coatings on the inside or out. In fact the bottom if my car has held up better and stayed cleaner than the painted body.

[wareagle]

What they said Plus, I went an extra step and brushed in rust encapsulator inside my frame rails. Figured what the hell, right?

Just a tip, but you could use self-taping sheet metal screws to hold your floor in before you start welding. This will help you with alignment.

[wareagle]

Oh, and I highly recommended this product for punching your holes. A lot easier than drilling holes...

Northern Industrial Hole Puncher | Chisel, Punch Stamp Kits| Northern Tool + Equipment

[65fstbpieces]

Fstbk did you put the torque boxes in first or after the floor pan install? the pictures are great. I am rounding up the pieces to do my fastback full floor. The while I am in there approach I was going to ad the torque boxes. Thanks

[manley]

Do torque boxes first. I assume you are replacing the toe boards, also? Do torque boxes, then toe boards, then floor. Get the 2 piece, more expensive torque boxes. I bought the pre-assembled pieces and the flanges and such seem to be bent/cut to replace them as stand alone repairs/upgrades(in the case of 65-68). To be more exact, the flange that welds over top of the frame rail is cut out because you wouldn't be able to install the torque box unless you are cutting out the toe boards as well. Also, I think(?) the flange against the rocker is bent down instead of up, which also aids in installation because you would not be able to get to it if it were bent up in cases where the toe boards are not being cut out.

I wish i had known this before I bought the parts. The suppliers do not detail what the differences are. It all depends on how extensive your repairs are.

[Fstbk]

I did my boxes after the car had a floor and was square. Put your GOOD export brace (NOT THE CHEAP ONE) in place before you install them. I also changed out my front frame extensions/floor supports and tunnel cross member so they needed to be in place before the boxes anyway.

The only mod you do to the cars floor/toe boards is a slice right here to allow the boxes lip to protrude into the car. I removed the 90º bracket from the kick panel side so the box could sit flush.





This is what it looks like back-lit.




This is the lip I am referring too.

[wareagle]

Fstbk, and anyone else, are sub-frame connectors and/or torque boxes necessary if you have the 200ci engine?

[Fstbk]

I dont have them, (SFC's) and I drive my car harder than most people with no noticeable flex since I added the torque boxes and gussets to the front. (EDITED TO REMOVE CONFUSION, sorry)

Everything below this line is not intended to start a flame war.
__________________________________________________ __________________

To be honest much of this "Sub frame connectors are a must" concept is propagated by those that have never held a front frame extension (Floorboard support) and tried to twist it, not much strength there to attach to. If I were doing SFC's they would need to replace those extensions and connect to the front frame rail.

The best option IMHO is a convertible floor and inner rockers, but thats a bit of work.

[wareagle]

But you do have the torque boxes, right? Rear and front, or just rear?

[Fstbk]

I have added 68 style to both sides of the front, and added the gussets. The rear has original TQ boxes.

(This pic shows the final result after gussets and 3M sound deadener.)

[xcelr8]

My 66 didn't have torque boxes and I don't plan on putting them in. Think that will be a problem?

[wareagle]

Sorry, but what are gussets? And what type of 3M sound deadener did you use?