Floor Pan Replacement - where to cut?

[BillGrissom]

1965 Dart GT. Replacing the rusted passenger floor pan and need to know the best place to cut it at the top. My plan was to install the new pan all the way to the upper seam. I already cut it to the top and popped the spot welds loose along the frame rails, as shown. However, the top seam doesn't seem to come apart easy, and it is complicated since a splash plate comes to the seam, behind the front wheel (see photo from wheel side). (The strut tied below pan protects the fuel lines while cutting/welding).

For those who have done this job, would it be simpler to cut it short of the seam, a few inches below (above the red line), and make a butt weld there? I can still get a copper spoon up there from below to avoid burn-thru. The metal is sound once the vertical turn starts.

For materials, I have the $55 floor pan shown, that is sold on rockauto for "62-65 Dart, Lancer, Valiant". It is only a rough fit, and will take some bending and beating. I have the cheap $90 wire welder from Harbor Freight I have used on other jobs, including sheet metal. It does sputter and spit, but works. I have the interior stripped, side windows out and the front and rear windows and dash covered with plastic sheet, so a weld splatter doesn't mess up my glass or dash. I will sand-blast and paint the frame rail interiors while I have the opportunity.

 

[Hell_Fish]

A friend just replaced the drivers side in my 65 Cuda. I had seperated the pinch weld and removed the lower lip. I shouldn't have bothered. My friend flattened the lip on the replacement pan and covered the pinch weld for a more solid seam.

 

[BillGrissom]

Thank Hell_Fish. If I understand, I should cut the existing floor ~1/4" below the upper seam and overlap the new floor pan there and weld it along the seam. That seems stronger and easier. I might beat the existing pan in a bit so the new pan sits flush on the sides.

I don't want to overlap too much because I don't want to trap bare metal where I can't prime. I understand there is a special weld primer one can spray to help protect blind areas like that. Where can I buy? The new pan has some type of grey primer. Does anyone know if that is similar? Otherwise, I will first coat inaccessible areas with Rust Destroyer since good to 800 F.

 

[Hell_Fish]

Paint or welding supply will have the weld through primer.

 

[jefflock]

Eastwood sells a weld thru primer.

 

[stroker_valiant]

All Orielly Auto Parts will sell weld through primer in a 3M brand.

 

[furyus2]

I like your idea of cutting the pan below the seam and butt weld it. looks nicer when ground down and like you said, no place to trap moisture

 

[66 Dartman]

if the factory seam is solid i would leave it and butt weld your patch panel in, Here's a couple pic's i made my own pan and butt welded it in. Hope this helps some.

 

[BillGrissom]

Thanks for all the info. O'Reilly's is easy.
I know my result won't be near as nice as 66 Dartman's. I can't even tell where he repaired it. At least carpet and undercoating hides a lot.

 

[mopar410]

I cut out all the floor to fit the new pan,reason I did this is because I wanted the most new metal in the car.That being said the pan I bought from rockauto was a full front side(I installed both front pans seperately) the pan you picutred doesn't have the lips on the side and top area so IMO you should leave the pinch welds and trim the floor 1/2" below it then place your pan in the car and outline the pan with a marker(fine tip)Also cut the end of the pan to match the floor cut..When you cut the floor cut it about 1/8" on the inside of the line then go back and trim it as needed.I personally wouldn't overlap the floors,too bothersom sealing the top and bottom.You will still need to stitch weld around till its complete.

 

[BillGrissom]

mopar410,
Thanks for the info. The rockauto pan actually is long enough to reach the pinch-weld and fold a lip, but I will try the butt-weld. I did some butts OK on another car and once welded two exhaust pipes butted together OK, so I am confident. I will hit it with little stitches and let it cool between while I do other things, to avoid warping. I don't like over-lapping.

 

[Hell_Fish]

Here is a shot of mine. All panels are overlapped.

BTW- The shop made a 67 panel fit well.

 

[4spdcuda66]

Mine are home made. Lap welded on both sides.