USA 1970 911T - the Tangerine Dream

[RobFrost]

It's difficult to understand how a panel manufacturer can make the rear floor a whole 10-15mm narrower than the front. Which means unnecessary work straightening out the flange and bending a new one.



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[Gary71]

Does it measure narrower, or just have a gap to the sill?

If the panel is genuinely narrowing down it’s length then I’d be tempted to stop at this point and buy another one that’s the right shape…

Reshaping those flanges successfully is going to to take so much effort and be so hard to get right.

I know the Restoration Design floor repair panel is straight.

[RobFrost]

It's straight but narrower than the factory panel that came out. I'm 100% certain the sills haven't spread out because the front floor's still in, literally two inches away from this span.

Also, the flanges are enormous - about 20-25mm all round. I assumed this was so as to cut off the excess but maybe it's to leave you some leeway to reshape it, or maybe they were folded at the wrong place.

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[deano]

I used a couple of small sections out of one of those green panels (just a rear left). The features were very dull, compared to the original floor section, and were not in the exact same locations, so I had to reshape to get it to match the original right side. The steel was like toffee too, compared to the original. It will probably be fairly simple to move the flanges 5-7.5 on both sides, and any imperfections will be hidden under the sills.

Maybe the Dansk panels are just the same, I don't know... I think I might have sent the green one back and taken a chance on the Dansk being a little bit better...

[RobFrost]

Thanks Dean, reassuring it's not just me then. Mine seems very rigid - maybe they've increased the depth of the stampings, or maybe because I'm using it whole instead of small sections. Either way it'll be a huge improvement over what came out once it's welded to the intermediate sills, within-sill supports, inner sills, centre tunnel and rear seat well, especially now they're all fresh steel.

What I can confirm about these green Retro Line panels is you have to get all the green paint off, otherwise it flakes off after fitting, as I think you warned me in relation to the front right corner, which I had already painted over. That will now be stripped bare and epoxied over again.

[Gary71]

Once you adjusted your floor panel I’d recommend replacing the flange on the bottom of the sill. It’s going to be challenging to get a good clean with the frilly remains after the spotweld drilling.

[RobFrost]

Once you adjusted your floor panel I’d recommend replacing the flange on the bottom of the sill. It’s going to be challenging to get a good clean with the frilly remains after the spotweld drilling.

Do you mean getting it clean for a good electrode connection, a tidy bottom edge for cosmetic purposes, strong for structural purposes, or all three? Some spots didn't come away cleanly but I only drilled through the flange with a 2.5mm drill bit, which I used to pilot the spot weld cutter from the other side. I'll post a photo showing the face, but I was pretty pleased with how well I managed to preserve it. I was planning on using a dolly and hammer to straighten out the undulations and I have a wire wheel for the grinder which is brutal at removing paint and underseal.

[Gary71]

Once you adjusted your floor panel I’d recommend replacing the flange on the bottom of the sill. It’s going to be challenging to get a good clean with the frilly remains after the spotweld drilling.

Do you mean getting it clean for a good electrode connection, a tidy bottom edge for cosmetic purposes, strong for structural purposes, or all three? Some spots didn't come away cleanly but I only drilled through the flange with a 2.5mm drill bit, which I used to pilot the spot weld cutter from the other side. I'll post a photo showing the face, but I was pretty pleased with how well I managed to preserve it. I was planning on using a dolly and hammer to straighten out the undulations and I have a wire wheel for the grinder which is brutal at removing paint and underseal.

Last two

I found that even the neatest flange on the tunnel I drilled out didn’t weld cleanly back on again so abandoned it and replaced all the flanges. I tried plug welding back through the drilled holes which should work in theory, but in reality it was a spitting spluttering mess, no matter how much I cleaned and straightened it.

On this particular one I was in an easier place than you as I’d replaced the mid sill!

I’m sure you’ve already covered it but don’t forgot to pre-drill all the holes for the seat mount, mid sill and around the structure by the torsion bar.

[RobFrost]

I had that massive spluttering problem when using the weld-through zinc primer from FROST Restoration - I don't think it was conductive at all. But it worked a treat when I switched to Plasti-kote zinc primer. The original metal's shiny once it's wire brushed, no pitting or corrosion here.



I've centre-punched the seat supports welds already but not drilled.

Did you open the floor and weld through to the bottom of the jack-receiving socket? The floor I removed had a half-inch hole cut out and welded through to the bottom of each one.

[Gary71]

Yes, the jack tube was welded to the floor as well.
It’s not fitted in the picture above as I was dry building everything.

To maximise welding success I’d recommend a small cone drill through each one of the holes to open them all out to the same size and get a clean edge without burrs or thin areas.

And agreed about weld through primer, my technique in the end was to spray everything, then dry build and mark the plug weld positions with a sharpie, take it all apart again and very locally clean back to bright metal.

[deano]

Those flanges look good enough to eat off of. Have you considered spot welding in-between the holes? If you do that, you don't have to worry as much about filling all of those holes completely. And you don't have to remove the galvanising from the green floor if you use spot. If you try to fill the holes with a proper (high current) plug weld, you will inevitably end up burning away the bottom of lots of those holes.

You probably know already, but paint or galvanising around the plug weld hole or on the back metal causes spitting. If it is clean, then a shorter higher current burst usually does the trick I find.

My original jack tubes were welded to the floor, as per Rob's, although not very well, and from the state of the tube there was moisture collecting there and both tubes were toast in that area but surprisingly the floor was OK.

[RobFrost]

tbh I am tempted to hire a spot-welder for a day because I prefer the way it pulls the metal together and creates interference and tension between the two surfaces very locally to the weld. Another issue with plug-welding the holes is that the original welds were rarely placed uniformly and often close to the edge. On the other hand it suits me to dip in and out of the job as I feel like it, which I can do with my own gear.

[911hillclimber]

I spot welded all my floor repairs, inner sills and the outers way way back.
The access for the one electrode that is close to those joints is very tight, and easy to end up with the spots very close to the flange edges.
The welder quickly gets heavy....
Still, all ok after 33 years!

[RobFrost]

It took around an hour to move the flange 5mm on one side. A hypothesis as to how the panel could be off, is that maybe they now stamp the pressings into the floor a bit deeper than they used to, which would shrink the panel a few mm more.

Anyway, with pulling the panel tight it was only 5mm. I have no folder, nor a metalworking bench so I clamped it to some steel section I had and then hammer and dollied it square.


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[911hillclimber]

In 1988 there were no replacement panels, so i hand made both floor edges in the same manner, angle iron and good straight wool with careful hammer work. Worked out great.
I removed about 80mm of the floor edges and front/rear corners.
Gas welded the floor together and spot welded the sill set of flanges, all normal stuff in the day.