[north]

As for those free spinning screws I’d imagine it’s to allow for the thermal expansion and contraction of the tank?

As for the clip on the wires near the trunk latch I suspect they were never used. I’ve got many survivor 69 A bodies and I’ve never seen any mark indicating it was attached to anything. Perhaps it’s the same wire used on 68’s or some other model and they just never bothered to delete the clip from the design?

[Greg Reid]

My '68 has what appear to be the original plugs at that location near the trunk pass-through and no clip.
As for the vent tube filter, I like Patton's idea of using the breather vent material. I rolled up and inserted a piece of Scotch-Brite pad for mine.

[Shiny]

Thanks to both of you.

I'm not sweating the clip and don't even know if it's original... was just curious.

As to the tank strap fastener, clearly they wanted the strap tension transferred to the rear bracket by the strap loop and not by being clamped. My guess is they simply didn't want it to slip after it was tensioned by the front clamp and bolts. I think it's pretty clever - retains the loop but doesn't clamp and installation is no different than any other fastener.

Apparently it was important enough to tool a special bolt. Like most of this stuff, I'd love to know the back story on this decision. Must have involved rattling tanks or worse..

For the vent, I am following this photo posted by 85_SS in this thread:

http://www.forums.maxperformanceinc....d.php?t=398479



Yesterday I asked the guy at O'Reilly's for a fuel-resistant filter material. He walked to his shelf and grabbed a breather just like it. Then I found this photo on the old thread and made me feel a little better.

Should have the tank install finished soon and I can move on to my next adventure.

Mike

[north]

You can do like the factory did and slam a deep staple into the hose to prevent the breather material from moving.

[P Glade]

The rear-strap screws are designed that way so there is a smooth surface (on the bolt shaft) where it passes through and contacts the FIRST HOLE in the strap. If the screws were fully threaded the threads would grab into the first hole (as well as the second hole) and end up SPREADING the strap as the threads worked against the first hole.

The smooth part of the screw shaft prevents that from happening......you only want thread/thread contact with the SECOND HOLE in the straps.

[north]

That’s exactly it P Glade, forget my earlier opinion, too long since I looked at that arrangement!

[Shiny]

That's a good point but I'll have to think about it as my interpretation is different.

The assembly note clearly says "until the screw spins freely", which to me means the threaded section passes completely through both holes. I think the fastener may have a smaller diameter section that is long enough to pass through two thicknesses of strap.

If it were only about avoiding "pushing" the tail during assembly, a clearance hole in the strap would accomplish this. In fact, the repro straps I bought did have a clearance hole. But with the supplied "normal" (fully threaded) screw, the strap was clamped. Getting it to spin freely would mean stripping it which would not be a good idea IMO.

I'll have to go run this special fastener through the old strap and watch what happens.... stay tuned.

[Greg Reid]

Originally Posted by Shiny

That's a good point but I'll have to think about it as my interpretation is different.

The assembly note clearly says "until the screw spins freely", which to me means the threaded section passes completely through both holes..

Yeah, that's the way l interpreted it.

[Shiny]

The fastener is indeed designed to spin freely and NOT clamp the strap.

I could not say if the straps I removed were original or aftermarket. The only marking I found was "W". There definitely was a clearance hole on the fastener entry side of the bend:



The start of threads on the bolt is ~0.7" from the flange. The strap is ~0.095" so there is about 1/2" of "thread-free", reduced-diameter bolt.

3 washers are thicker than the bracket on the car. When I started the bolt, it cleared the outer hole:



When tightened, the threads pulled through the strap and then "exited" the far end without fully clamping the strap. The bolt clearly "spun freely", effectively being a "self-stripping" fastener. The threads that were formed in the strap allowed the bolt to be removed easily:



Net:

- The strap is not clamped "by design"
- The special fastener makes it all happen
- The repro fasteners with full threads don't accomplish the assembly as intended by Pontiac

I'm not too worried about any of this, but as I said, I see this as a very clever system to assure the strap tension is held by the bend and not by the clamped connection. Why? Dunno.....

I can't read the part number for this fastener (#13 on the 1970 assembly drawing). It looks like 399782 ??? Anyone have a clear PN for this?

Mike

[Shiny]

Wonder if the idea was to limit the bend radius in the strap?

If so, fully clamping the strap with the aftermarket screws may "overstress" the strap at the bend? I doubt it would cause any damage but just a thought... I think a general guideline for forming sheet steel was to keep the radius greater than 3 times the thickness ??

Mike