Technical Fixing rusted floorboards

[smahaley]

Piecemeal or buy new pre-made floorboards?

1978 124 CS1- and I’m slowly addressing rust issues. I’ve started on the floorboards and would like some opinions as to my next best step. The video is of the passenger side:

Thanks in advance!

 

[bugsymike]

I would say if good quality replacement floor pans can be sourced of similar thickness to the original, so you can cut away cleanly all the rusty metal , maybe using a plasma cutter, then a good welding job followed by rust treatment and sound dampening like original you will be well pleased with it.
Much better than trying to patch up or bend steel to the factory shape.
Mind you I was at a friends today and he is rebuilding a Jensen Interceptor and making up wooden formers to shape steel to factory design, a lot of hard work, but he is well experienced at the task.
Regarding gearbox mounts, providing you can get the postioning correct, it may be possible to cut around the thick area with the studs in from the old parts and drill holes in the new panel to place those fixings down through and weld into place, assuming they don't come on the new preformed panels.

 

[smahaley]

Thanks, @bugsymike - I’m really on the fence. I may try one area to see how I do, since I have the materials already for that. I don’t need or want to make it look like original - just solid and weatherproof…

 

[bugsymike]

Thanks, @bugsymike - I’m really on the fence. I may try one area to see how I do, since I have the materials already for that. I don’t need or want to make it look like original - just solid and weatherproof…

If you are reasonable competent with your welding and take your time it should be fine, just don't set fire to the place.

 

[Twink80]

Piecemeal or buy new pre-made floorboards?

1978 124 CS1- and I’m slowly addressing rust issues. I’ve started on the floorboards and would like some opinions as to my next best step. The video is of the passenger side:

Thanks in advance!

The usual cost vs time vs quality weigh up! I don’t know what replacement panels are available and if they will cover all the area you need.
Looks like you could cut around the crossmember and seat mounts to maintain some datums. You may need to temporarily weld some braces in like the gearbox mount to maintain its location
You can also make cardboard templates for the more complex areas eg curves where the floor joins the sill etc
You might also have to consider which side to weld from as the weld side is sealed the otherside is open and craggy so a good dirt/moisture trap. You can get automotive body sealer on eBay (similar to OEMs use) to seal the seams after welding. Its like a mastic but sets with a skin

 

[smahaley]

Thanks, @bugsymike - I’m really on the fence. I may try one area to see how I do, since I have the materials already for that. I don’t need or want to make it look like original - just solid and weatherproof

The usual cost vs time vs quality weigh up! I don’t know what replacement panels are available and if they will cover all the area you need.
Looks like you could cut around the crossmember and seat mounts to maintain some datums. You may need to temporarily weld some braces in like the gearbox mount to maintain its location
You can also make cardboard templates for the more complex areas eg curves where the floor joins the sill etc
You might also have to consider which side to weld from as the weld side is sealed the otherside is open and craggy so a good dirt/moisture trap. You can get automotive body sealer on eBay (similar to OEMs use) to seal the seams after welding. Its like a mastic but sets with a skin

thanks @Twink80 - I think I’m going to first clean more and cut out some segments to see if I can create some easy shapes. I have cardboard for making templates - and yes I think I’ll have to get creative about the trans support member bolt locations - maybe even get new metal in and then reestablish those points with new bolts…