A treatise on early 911 longitudinal and rocker replacement

[Zeke]

We have seen a few different approaches to sheet metal replacement on bodywork and the inner structural components of the 911. The early 911 to '73 uses a welded door threshold/rocker panel as opposed to the '74 and later bolted on type.

Behind a permanent panel such as the rocker is likely to be an accumulation of dirt and rust, depending on where the car has been living and driven. Certainly salted roads are the bane of any unplated metal, especially concealed cavities.

We have seen a few different approaches to sheet metal replacement on bodywork and the inner structural components of the 911. The early 911 to '73 uses a welded door threshold/rocker panel as opposed to the '74 on bolted on type.

Behind a permanent panel such as the rocker is likely to be an accumulation of dirt and rust, depending on where the car has been living and driven. Certainly salted roads are the bane of any unplated metal, especially concealed cavities.

So, if you end up with a car that has such rust, you have to find it and eradicate it. A lot of the metal will be eaten away to the point of needing replacement. The purpose of this thread is to show a little of what I did and gather some thought from others on the subject. Eventually, the information here may be edited for a tech article. There are some tech articles for floor pan and longitudinal replacement in the 914 tech section, but nothing in the 911 section that I could find.

This has been discussed a lot, but the threads are scattered throughout the archives. One issue is whether to drill out spot welds or cut near the seam and grind. I used both methods in this most recent task.

Let me
link to the beginning of my project to avoid being redundant.

The first pic shows some of the 100 or so holes left by drilling spot welds on the inner and outer rocker ass'y. I guess one can use a special stepped bit, but they don't last long and are hard to sharpen. An ample supply of bits, a good drill motor and a drill bit sharpener will make this job go easier.



Here's an inner long from Pelican Parts that is being readied for installation.



I'm holding it down to reveal the cut off original longitudinal member that I'm using as a welding flange. Notice this side doesn't have all the spot welds drilled, just the ones needed at the ends. There is also a hand punch laying on the sill that I used to punch holes. This side will be a lot easier due to the flange. There is no reason to offset the piece or the flange.



Here's a cross section taken from a parts car. At the top, three members of the structure come together and they are spot welded every inch on the top surface and in the door seal channel. You can look back to the first pic and see what it looks like with the inner and outer rockers removed. The door sill is attached to the floor pan and that is the third member shown at the right. The tube for the heat remains in the section. This is where the muffler/heater hose fits on that runs the length of the long.



All clamped up and ready to plug weld the punched holes. You'll notice I didn't replace the jack reciever and support on this side as they were OK. I just shortened the inner piece and wedged it into the jack receiver support



The rocker is now in place to check the door gap. You must have the door on the car at this stage and aligned as you want it with the lock pillar.



It's plug welded now and the lap seams are welded here and there for extra strength.



I'll dress the welds with a grinding wheel and prime before shooting the body schutz (underseal).

Thanks to those that got me this far and please post your unique procedures for doing this job.

[nostatic]

jezus h. criminy Milt, you are a madman. Is there going to be any original metal left on the car when you're done?

Drilling out spot welds is a pain. I think I'd go cutting...

[dtw]

Looks pretty much exactly how I did mine, Milt, save for the inner rocker did not need replacement on mine. I was able to patch it up.

Nice work. Drilling those spot welds is a royal pain, but well worth it in the end.

[H.G.P.]

Did you coat the inner before installation, if so with what?

[toolman]

Good work Milt, I know what your up against. You might want to check into a Zinc "weld through" primer for some added protection.

[niner11]

Milt thanks for the pics and all of the documentation you have provided. After doing an early Z car and seeing what lurks behind your rockers I will have any future restorations dipped to see what I've really got as a starting point.

DTW, nice website. Any updates on your engine rebuild or restorations?

[Zeke]

Originally posted by H.G.P.
Did you coat the inner before installation, if so with what?

I have my own theory on that. First of all, there is no way I will attempt to rid the car of very bit of rust. There will be some lurking in the car always until it is taken completely apart and media blasted or dipped (which, after some research, I 'm very much against).

So, as the story goes about a chain being only as strong as it's weakest link, something will appear someday depending on how the car is cared for. I don't intend to ever drive in the rain and we con't have snow or salt in Long Beach, or anywhere I'd go in the car.

That being said, the bare metal pieces I'm fabricating and the primed and/or plated pieces I'm welding in should last as long as the weakest original part. That is not to say that I want to do this again, it is only to put things in perspective. This is not a restoration for a museum, this is a necessary restoration so I can drive the car agressively and know I've got a good foundation around me.

As protction against future rust, I will prime and undercoat the exposed areas with the proper materials, and use body cavity treatment such as Waxoyl (sp?) in the concealed areas. It only takes an 1/8th inch hole to apply the cavity wax. Actually, the compound I prefer at this time is a cosmoline based spray I get from Aervoe in Sparks, NV.

That was a good question, thanks. I will have a couple more pics of the work soon. I expect the right side outer rocker to arrive any day and I was going to finish that side and complete the process of documenting the two different approches to doing this work.

[billyboy]

Milt, I was curious as to what size welding wire you use for body repairs. Do you use bare wire with CO2 or flux cored. thanks

[TimT]

Milt, impressive... also reminds me of what I have gone through on my car these past few years... I swear those pics could have been taken by me ...except that you take better pics than I do.

that overhead weld on the lower part of the rocker was a pain in the coconuts, because with the torch "where you think it should be" you cant see the wire

I came up with a solution for this... I cut a mig nozzle on my band saw at about a 45 mitre. that way I positioned the sharp side of the nozzle up, and I could view the wire, the weld joint, and the puddle.