Sheet metal screws through firewall and footwell. Correct?

[Grigio330GT]

Much of the interior trim in my 330GT is held in by sheet metal screws, and many of these protrude through the floor, firewall and footwell housings on my car. Over the years, it seems that anytime someone worked on the interior trim and had to remove these screws, they would subsequently re-install the screws without re-using the old hole. This has resulted in multiple holes all around the various screws. This is an example from the driver's footwell:

footwell walls.JPG (81.12 KiB) Viewed 12559 times

So this leads to several questions:

1. What is correct- are sheet metal screws really just supposed to protrude through? Or are there maybe pems that are supposed to be there? I should have been more observant over the years, but have never carefully inspected other 330s I have see
2. If it is correct - is there any place I can find out how many/which screws the factory drove through?
3. I plan to patch all the "extra" holes with epoxy - (JBweld). Any other suggestions?
4. Would it be terrible to bond m3 weldnuts to the firewall (boss facing out), and use a machine screw?

Slab_base_weld_nut.png (211.07 KiB) Viewed 12559 times

[330GT]

From my experience, Pininafarina (body maker) used metal plates that were spot welded or riveted to the backside of the piece that the screw fastens to:

SplashShield12_small[1].JPG (8.19 KiB) Viewed 12544 times

The plate was typically about 1/8" thick and had a machine screw thread (usually 4 or 5mm) tapped in the middle.

If the metal being fastened to was steel and thick enough, a nut was just welded over the appropriate sized hole. In other cases, a square nut was captured in a spot welded or riveted on box. This allowed the nut to move around to accommodate slight location variances. Examples of these are nuts that hold the headlights in, attach the grill to the body and transmission tunnel to the firewall and floor.

[Grigio330GT]

Kerry

Thanks for the note. My car has a few of the captured nuts you mention, but not for all of the carpet button and trim screws. Those are the ones that I am trying to figure out. In any case it sounds like your car does not have any sheet metal screws sticking through the foot-well housing (under the brake booster)

Dave

[tim]

Greetings... On 5769, the carpet snaps are secured by what appears to be sheet metal screws on the firewall. The panels are coated with under coating and the pointy end of the screw sticks through maybe 1/8 inch. Not real evident due to the thickness of the under coating. The snaps on the floor are also secured with what looks more like a small shanked wood screw into the floor panel which is thicker. On the trans tunnel, what looks like self taping machine screws go through into a tinnerman or "speed" nut. Hope that helps.

Tim

[tyang]

Hi Guys,

In my opinion (you know what they say about opinions!) Sheet metal screws that were used for interior pieces like carpets and trim panels were often cut flush with a pair of side cutter pliers after they were screwed into place and if they protruded far out the other side. There's only one place these sheet metal screws can poke through, and it's at the transmission tunnel. ( In fact, I cut myself just this week from one of these screws because my upholsterer didn't cut one of these screws down! ) The floorpans are double layered, so rarely do you see a screw poking through. Screws like the ones to hold the transmission tunnel in place were capture nuts with threaded screws. The screws holding the splash shields were also threaded, but the receiving threads were tapped into the support structures. Certain screws did have support backing sheetmetal as pictured previously, but I can't think of where I saw them.

Tom

[enio45]

I know this is about 330 cars, but i can tell you that on the 250 Ellena i have, all the screws for the tunnel that go in the floor
are sheet metal screws with no captured nuts, and are not cut off on the back side etc.....

the firewall on the other hand has 4 holes with captured nuts type for the front edge of the tunnel to secure to

[330GT]

Hi Guys,

...The floorpans are double layered, so rarely do you see a screw poking through. ...

Tom

The later (interim and series 2) 330 GTs have a fiberglass floor. The carpet snap screws go through and stick out underneath. I've never scarred my hands on them, but if I ever do, I'm sure that the cut-off wheel will be wracking off the ends post haste.

[Suebian330]

The backlayered metal strips you find as I remember only for the mud shields inside the fenders. It is tapped M5. See pic

DSC01327.JPG (36.79 KiB) Viewed 12402 times

[Suebian330]

May be now pic in better size

DSC01327.JPG (23.59 KiB) Viewed 12401 times

[Grigio330GT]

My car has all the correct machine screw bosses for the major hardware. It’s just the carpet trim screws that’s protrude through the footwell walls. From everyone ones responses, it seems that is not correct - the screws should be very short so they go through only the 1st layer of the double wall. So I will patch the engine-bay side of the foot well with epoxy and then find the appropriate short screws for the inside....

[Melchior]

Hello Tom,

this thread would show the Information I look for - what are the correct screws that secure the transmission tunnel to the floor panels in a 250 GTE? Is there any possibility to make the pictures in this thread visible again?

Best regards, Martin