I am in the process of replacing the floor pans. I have the car on a rotissiere. I can drill out the spot welds with my Blair spot weld cutter. This is still a lot of work and my elbow is protesting. What if I were to cut the pans out but leaving the strips of metal where the spot welds are and weld the pans ofer the top. Is this ill advised? My thoughts were to save time and maybe more metal is better. Less chance of weaking the long with welding heat.

I don't think there would be any structural problems with what you suggest.

Of course, a future owner might raise an eyebrow at the repair.

I have a ViceGrip-type tool that's used to create a "step" in sheet metal. You could create a step and lay the pan in snugly. I believe that would help make your welds neater and the area stronger.

By all means drill out the spot welds! Obviously at the front pedal cluster you will have to cut it but the ease of installation will make spot weld drilling well worth it. (spot weld the pan back in as well just like the factory or maybe solid weld if racing).

In the body shop leaving the strip of metal is a widely accepted production method for changing large panels like quarter panels and roof skins. I must have done 100 or more rolled over Broncos like that. This allows the factory integrity to remain while changing the damaged panel.

The concern would be, that with a floor pan you may have hidden rust between the layers of metal. Also, because there is added stress by passanger weight and vehicle dynamics, there would be a concern that the new pan would only be attached in places to the left over strip of floor pan and not the structure.

I wouldn't be overly concerned about it. Just examine the areas between the spot welds. If they are bulging from rust, remove that section and clean up the rust.

Another method of removing spot welds I use is to identify where they are by tapping (gently as nt to damage the part you want to save) a sharped standard screw driver between the panel being removed (in this case the floor pan) and the structure beind saved. This caused a bulge around the spot weld. You can then take a 4" cut off tool or die grinder and surgically grind away at the spot weld until the metal is thin. I do a row of them and come back with either an air chisel, (mostly I just use a sharped standard screw driver it's neater and less damaging) or a sharped screw driver and slice the old panel off the body. This mostly leaves a small bump from the left over spot weld you simply finish grind while preparing the the surface to accept the new floor. After you get the hang of it, this method is faster than the spot weld drill and far less damaging. Actually I haven't used a spot weld drill for 20 years. Oh ya, and it's easier on the body!

In restoration work I always remove the strip but never use the Blair tool.

I guess that is what I will do. My Elbow will complain but I guess I can shut him up with beer later.

Has anybody used this, or something similar:
http://www.thetoolwarehouse.net/shop/STK-20015.html

I've used a die grinder, much like Rick's method but I've never tackled a panel as big as an entire 914 floor.

No but that looks like a nice tool. I'd still grind first to thin the panel being replaced. I think the slicing tool would last longer.

, especially about hidden rust in the seams.

Man I wish I had one of those seam busters 2 months ago!!!
I ended up grinding away each spot until I was at the original metal.

I have been busy removing the pans. I am making pretty good progress. I am glad I decide to remove the metal. The rust between the spots is not real bad but it is there. This would have been a weak link. I'm not using the Blair tool. I am using a 4" cuttoff wheel in my angle grinder. I cut on both sides of the spot. This weakens the metal between the welds and allows that material to snap out. I use the same wheel on the spot. I watch the color to see where the metal is getting thin and the spot weld remains (as was suggested here). Your inputs were helpful. Thanks

I have the same elbow problem. Glad the advise helped. Be sure to post pics.

Here are a few pics of my progress. As you can see, the rear firewall is total trash. I have new parts on order. You can see how clean the longs are. I didn't cut into it once. I think the Blair would have made a mess. This car had water sitting inside. The rear rusted as did the tunnel. The front floors are pretty good. There is some rust at the pedal mount place but no rust through. I have not decided to replace the front pan. I have a full front pan on order. My plan is to cut out the tunnel part and weld it over where I cut off the rusty one. This sounds like where I started this thread But I am only talking about the tunnel bottom. I am still a little afraid of doing unnecessary surgery (removing the full front floor). I also have new tubes for the tunnel. I will post pics of that repair. I figure it is easier to replace them when I install the rear outer firewall.

One more pic of the tunnel. This is a good view how the tubes run.

Thats a great pic of the center tunnel contents.

Are you sure your elbow problem is really at your elbo? I have had CRAZY nerve related pain in my arms- took back surgury one time and traction the next time to fix the nerves pinched by herniated disks.
After the surgury the releif was instant and awsome.
Ever have back or neck problems? We DIY914 types spend a lot of time contorted in bad positions....

I hadn't thought about my back causing the problem. You may be right. I have had back problems for years. My neck also has problems from a whip lash rear end accident 10 years ago. On the other hand, I am just getting old. My elbow really started hurting when I drilled out a LOT of holes in a donor part. It started then. I stopped working on the car for 3 months and it got better. My plan is to not stress it. Work in measured lengths. It is a little more fun that way.