Finally found a 69 240z, #51 Time to finish a 30 year multiple owner restoration.

[dspillman]

It’s all good, I am reading through and trying to learn as well, soak in what I can, I’m hoping to not have to pull apart the flexiflier joint, but will if needed.   The conversation is directly related to this build and others.

 

[Zed Head]

On 4/21/2024 at 1:05 PM, grannyknot said:

It is a complicated joint and difficult to open up to remove the rust.  I had one of my Z's dipped because of the same kind of rust and all the leaded joints came back empty. The place I used baked the car in and oven at 600-800F to burn off all the coatings before it went into the acid tank.  I'm still looking for the photos of that car when it came back, I'll keep hunting for them. 

The remaining question seems to be - what is under the lead?  grannyknot has seen it, apparently.  I think that most people are just used to seeing the lead filler and don't think about what's under it.  I'd guess it's more stitch welds but it might be spot.  Hope he finds those pictures.  Maybe he remembers and can describe more.

You should be able to melt the lead out and grind the welds down to open it up but you'd probably have to do more than one seam since any flexibility will be of low magnitude.  Could be a can of worms.

[HS30-H]

2 hours ago, Zed Head said:

The remaining question seems to be - what is under the lead?  grannyknot has seen it, apparently.  I think that most people are just used to seeing the lead filler and don't think about what's under it.  I'd guess it's more stitch welds but it might be spot.  Hope he finds those pictures. 

Posts nos. 88 & 89 in this thread answer those questions, I'd say. 

 

[Zed Head]

On 4/21/2024 at 1:05 PM, grannyknot said:

That rust hole in your pic of the D/S roof is just above where the roof panel and the C pillar were joined, it was soldered together with lead. Some have said over the years that it was done that way to allow some flex in that join, others have said that it was just the technology of the day, they both sound plausible to me.

I was talking about the C pillar.  The original joint of concern, and the start of the lead focus.  I don't see a lead-free but intact C pillar joint in anybody's pictures.

[Patcon]

5 hours ago, Mark Maras said:

 I've never had a good look at that seam but I vaguely remember Matsuo-San talking about the welded seam options. Butt or flush lap seams would be too stiff so they opted to bend both sides 90 degrees (or possibly a standing seam joint) to join the two parts. @Patcon Charles, do you remember that part of the conversation?

No I don't recall that part of the conversation.

[HS30-H]

10 minutes ago, Zed Head said:

I was talking about the C pillar.  The original joint of concern, and the start of the lead focus.  I don't see a lead-free but intact C pillar joint in anybody's pictures.

You obviously don't see the drilled-out spotwelds either.

 

[Patcon]

I have seen pictures of the qtr to roof joint over the years. There have also been pictures posted up of roof cuts that show how many layers are in this area. I don't remember what threads they were in. It is a very complicated joint with multiple layers

[Zed Head]

Sorry, I didn't recognize it.  It would be nice to know if that picture is from a production car or somewhere else.  There's no identifying text for that shot.

Here it is, from post #89.  More detail would be helpful.  How much overlap is there in the joint?  What does the backside look like?

A good old rusty production car joint would be good to see.

[grannyknot]

Found them, not sure these are going to help much, seems like only some of the lead melted off. 1st pic is melted lead that had pooled,

 

 

[Zed Head]

That's two pictures of the C pillar seam area now.  The first one was the inside of the bottom half of the pillar, yours is the top part that gets treated with lead.  It seems like what yours shows is that the the outer/upper portion of the seam is welded, then covered with lead to fill the groove left behind.  Those blobs are probably welds.  So, both spot welds and seam welds are used to create the pillar.  A messy area to work on, as you said.  Hard to see how you'd get it apart without creating a lot of extra work.

You can see how the upper part of the "tube" that you show sits on the lower part that was shown earlier.  And there's rust on the weld blobs.  It might be crude brazing efforts.  Not an expert on welding methods, older or newer.

 

 

[Namerow]

14 hours ago, HS30-H said:

...and here's a right-hand rear quarter roof/quarter joint with rear quarter panel removed (spotwelds drilled out), blasted and etch-primed:

It's a complicated joint - the meeting point of roof outer panel, roof rear crossmember/hatch hinge mount/roof longitudinal rail/rear quarter. Perhaps not surprising that it required lead-loading.

Excellent photos.  Thanks for posting.  It is, indeed, a complicated joint.  I'm always impressed by the skills of the manufacturing engineers and designers who (with little credit) develop such schemes and make them ready for mass-production.

I've often wished for 'exploded view' explanations of how the contributing panels come together at complex joints such as this one (another good example is the 'dogleg' behind the lower-rear door area).  Unfortunately, it would require either: a) an informed industrial artist (similar to the person who created the drawings in the parts manual), or; b) a photographer in possession of all of the individual panels/stampings.  Alas, the chances of either happening is remote. 

Edited April 26 by Namerow
more discussion added

[grannyknot]

8 hours ago, Zed Head said:

 And there's rust on the weld blobs.  It might be crude brazing efforts.  Not an expert on welding methods, older or newer.

 

 

 

Those are rust stains from the rinse water draining off, I've never found any braze that looked like it came from the factory.