Lots of Rust to Cut Out

[WHFred]

Hi;

I'm restoring a 69 srl311 that has quite a bit of rust and rot, and some pretty bad previous attempts by POs to cover up the problem rather than fix it.

Case in point - the body behind the upper fenders just under the cowl and running down to the front of the rocker.

Can someone point me to a picure of what this is supposed to look like? That large diagonal opening looks to be original with supporting metal around the edges. What was it for? I'll reproduce it in new sheet metal and weld it up, but not sure why that opening is there. Looks like it's only present on the drivers side.

I'm guessing that since that upper horizontal support member is rusted out on both sides of my car, this is probably common for roadster owners. Again, I'll fab a new support for both sides.

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[Bwk2000]

… Can someone point me to a picure of what this is supposed to look like? …

You can make it out pretty well in this photo …

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[Bwk2000]

P.S. The brackets are the same on both sides for ‘68-‘70

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[Nissanman]

You could easily adjust the design of your replacement panels to avoid any dead flat horizontal surfaces that are really great in collecting moisture and debris. As you probably realise, it is imperative to re-instate the structural integrity of the body but you don't have to re-create the original design problems.
A case in point is the leading edge of the sills or rocker panels.
They were factory designed to be almost contacting the inner surface of the lower front guards, a really great debris trap.
When I manufactured replacements for my car I designed them with an 8 to 10mm gap from the adjacent panel to allow debris to fall through.
A pair of raised metal brackets were welded onto the sill to mate up with the stock mounting holes at the base of the front guard.

RHS sill front cap.jpg

Don't be reluctant to re-think the design.
Subtle changes are worth the effort to ensure the issues never happen again

[WHFred]

Thank you all for the pics and feedback. I'll post pics of the progress! I totally agree that recreating design flaws is maybe useful if you're a purist, which I am not. I really don't like how the cowl just dumps water onto the structural supports just underneath them on the inner fender. Has anyone designed an elegant way to channel water down and out from the cowling?

[WHFred]

Two follow up questions -

On the kick panels there is the rather large diagonal opening that runs from high to low as it goes from front to back of the kick panels, and they are enclosed with a U shaped structure that is spot welded. What is the purpose of these openings? I'm tempted to reproduce my kick panels with the U shaped structure, but without the openings.

Second - these structures over the openings have two holes in them. Mine are completely gone so I have no reference. Were these holes used for anything?

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[toadman]

Those holes serve no purpose other than to collect water when driving in the rain (which I never do) and proceed to rust out our cars (which it has done). I covered mine with silicone to plug them up years ago. Unexposed sheet metal surface inside those channels had zero rust protection. Maybe some folks on the forum will see them as significant for structure, but structure is no good if it rusts away. The holes were at least most of the problem. Big hole above however is for the antenna feed. I did have to weld some sheet metal on the inside years ago because of that troublesome channel (and its holes). Good luck with that rebuild, if you can reshape and rebuild that structure, you’re a better man than me. Keep us posted.

[Gregs672000]

Isn't that where the antenna mount goes?

[WHFred]

On my car the antenna exited from a grommeted hole high up on the panel which I'll reproduce. I'll go with my instinct and put as much structure back into this part of the body as I can while avoiding unnecessary holes.

When I mic the existing metal I am coming up with 20ga thickness (.036 is what I measured). Can anyone confirm that this is indeed what the entire body is made from?

[toadman]

Antenna mount is threaded hole just above front rocker cone, 3” bracket used. Metal thickness sounds right, but I think that common sheet metal around that thickness is a little heavier, which is a little more easier to weld. But still challenging to weld to the thinner stuff.

[WHFred]

Making progress! Not bad for one weekend. That is all new metal, hand shaped.

Welding 20ga is not too bad, but it's impossible for me to butt weld to the existing car metal. It's just too fragile and brittle. I'll have to plan on flanging the edges and doing overlap joints with spot welds when I get to the floors.

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[Nissanman]

I suggest you cut back further to sound metal before you do any welding.
You need to do that for two reasons at least:
1. to make sure you can weld properly to the old and new metal and
2. you need the integrity of the weld to be 100% or it won't achieve sufficient strength.
This is a structural area and as such needs to be repaired correctly.
Just what I experienced when repairing my panels.

[WHFred]

Thank you for the input. I know in the floor I'll be replacing all of it and probably coming up about 2" all the way around, which looks to be sound metal.

[Nissanman]

If you do end up doing lap joints in lieu of butt welds, make sure you prime the joints generously before you use a seam sealer.
You want that area well and truly corrosion proofed before you cover it over.

[fairlane292]

Outer body panels are prob 20ga, if that (I haven’t checked yet, might be 22ga). The structural sheetmetal on the car is 18ga not 20ga but 18ga that has had just surface rust and media blasted can be quite thin and thus very tricky to weld. Try not do any grinding on the 18ga as you are just making thin sheetmetal thinner. Butt joints need to be tack welded at alternate spacing and blowgun air cooled. The tacks can be ground down while barely touching/grinding the surrounding 18ga material. The car body shell structure is essentially overlap with factory spot welds (you can see them everywhere). You can mimic this by using overlap with plug welds and have almost no grinding. If you ever cut factory spot welds on even a basically rust free car and separate the seam you will see light rust on the two mating surfaces. It’s near impossible to prevent this but as one person mentioned you can start with primer. You can use weld-through primer on both the mating surfaces, then after welding, clean and reprime with expoxy primer. Adding a very thin bit of seam sealer in the seam and if the area is not one that is done in finish topcoat (firewall, floors, inner trunk are OE in finish topcoat) you can spray a coating like Lizard Skin. It’s similar to the insulated undercoating used on the underside of the hood and that used in the wheelwells but it’s a bit finer than typical bed liner type coatings.

Rust repair is very time consuming and often joints are going to start rusting soon after the work is done, you just won’t know it. If the car is real bad as yours seems to be I would strongly suggest getting a body shell out of the south or west, fix the few small areas of perforation or rust-though. There’s no substitute for original rust free body structure and panels. Just my .02.