Yet another rust question

[rick b]

While working on removing the spring plate hub on the rear suspension on my 1970 911, I spent a little time wondering how I am going to fix the small holes that appear on the bottom on the longitudinal piece that the torsion bar goes through. Originally I though that I would just weld on pieces of metal as I would on other sheet metal repairs. Then it dawned on my that this is a hollow section that runs the length of the car (or a long part of the length). Since there is a hole, this means that water and salt once got into the hollow area. Should I take the time to open this piece up further and try to clean out the inside? Maybe even try to prime / paint the inside prior to closing / welding the holes? The sides and tops of this piece appear solid as do the rear seat buckets, and the rear cross panels that support the rear seats.

Thanks.

Rick

[classic]

Rick,

It sounds like water has made it's way in there, by your discription, rather then the other rust seen in that section from people trying to jack the car from that point compromising the undercoat.

The rocker is a pretty complex section, and can allow water to get into the longitudinal section.

Open up the outer section, and have a good look inside, clean treat and get some good cavity wax in there.

If you see the bottom edge compromised, you're going to have to open it up, as it's a tripple section, with the internal section giving support to your torsion tube.

[jerryg]

Rick

While restoring my '67 911S project I encountered a real mess in this area. I ordered replacement panels from Restoration Design and was surprised at just how long the outer panel is. I have a picture enclosed (I hope) to give you an idea. The replacement kit for both sides includes two inner panels that go around the torsion tube. For a pretty reasonable price, it would give you a piece of mind.

Jerry T

[66S]

If you are just replacing the bottom there isnt much room around the heater tube to spray the inner panels but you should coat everything you can while it is open. I like LPS cold galvanizng spray paint on clean metal, it dries quick and doesnt like to catch fire. POR15 over surface rust only, not on paint or smooth metal, it wont stick. I saturate welds with POR15 and wipe off the excess to seal any porosity.

[jerryg]

Thanks, Rick. Great recommendation. I have not had any smooth metal yet!!!

[frankc]

I have some pinhole rust in the same area that I was wondering how best to repair (difficult to see in photo). One option is to purchase the RD panels, but cut out and weld in only the bottom section of the panels where they are bad, instead replacing them entirely. Is this a reasonable approach?

[Fishcop]

This is possibly the most complex point of the car... It's essential that if you're going to have a go at fixing it yourself, that you do it right. As Tony mentioned, you need to crack that can of (tin) worms open and have a good look at what's under there - it is a location where three separate sheets of reinforcing panel meets. If there are pin-holes already there, then you're going to have much more to repair inside.

[frankc]

John,
Thanks for weighing in here - your thread over on Pelican is legendary.

RD sells the middle/internal structural piece along with this longitudinal section, but I was wondering how I would be able to get in there to weld the internal piece if I only replaced the outer section. From your picture it appears I will need to cut out a section from the inboard side as well (which is probably necessary anyway) to get at the middle piece, then weld in the new inboard piece. Does this sound correct?

[Fishcop]

Hi Frank, yes that's right.

It's a bit of a complex project. Unfortunately you need to crack it open to get an idea of the extent... if it's not too bad and the rust hasn't crept up to the torsion bar, the middle section can be "home made" out of some sheet and it doesn't need to be too pretty as no one will see it. It's worth noting that the middle section is particularly important if you're using a rear sway bar as it assists the inner section with the load. You can see in my photo that I got lucky and the perforated metal was all very low and only required small patches. I don't know how you can repair the center section without removing the surrounding layers (which are either reused or used as stencils to make new patches).

In the worst case you need to support the car on a bench and cut away all the metal from the torsion tube and the use the RD parts to rebuild - I really think that's a job for the pros unless you're a masochist like Timp See his mammoth resto here http://www.early911sregistry.org/for...S-resto/page10 there are some very good photos of the area and how the RD panels fit up... (You might recognize the octisserie )

[jerryg]

As another note, I would not do this job unless the car is on a rotisserie. When my '67 project was upright I did not appreciate just how bad was the damage in this area. I originally welded an inner panel that I fabricated and thought that it would do the job. When I rotated the car upside down and cut away the logitudinal sections, I knew that the entire sections on both sides need replacement from the inner to the outside. RD has a complete package with both inner panels as well as the outer section. I've been working from the front of the car to the rear and this should be the last major problem with body structure. Incidently, the Targa has an additional structural panel between the heater tube and the inner logitudinal that coupes do not have. That piece was also rusted away from the original floor and I am boxing a new section on to that panel going from the rust free portion to the new inner logitudinal. The Targa has it for additional rigidity and should not be ignored.

Jerry G (and the black 1967 911S Targa that was for sale at the 2013 Lit Meet swap.)