Just so y'all know:

If you only have the rear belly pan on your car, AND

You ignore the fact that the front bolts are really kind of stripped, AND

They fall out while you're driving down the highway at 55 mph-

The front of the pan will scrape hard on the asphalt. It sounds like your timing belt AND clutch have just exploded at the same time, and it'll get your attention fast.

I borrowed a coat hanger to wire it back up (to the sway bar) to get home, no harm, no foul.

Now I have to figure out how to re-thread the hole for the front corners of the pan.

 

This reminds me of the car I recently saw on the side of the freeway. The hood had opened at hiway speed, flipped up against the windshield and the part higher than the windshield flipped back, hitting the roof very hard. Needless to say the car was a total loss... no, it wasn't a 928, but a good example of what the power of wind can do. I'm glad you got away with only the damage you describe!

 

Rivnut is probably the optimum solution but for the sake of inserting just two nuts all the tools you need to buy to do it are a bit on the expensive side.

I need to do this myself at somepoint - the same connections on my SE are now M8 bolts - tapped into the frame rails - about 3/4 of one thread engaged. The easy solution is probably a piece of steel plate with an M6 nut welded to one side, then plate welded to the bottom of the frame rail with the nut engaged in a carefully filed hex hole in the frame rail. Thinking aloud you could probably just JB Weld the plate and nut to the frame rail. Tighten a well greased bolt through the nut first to hold the nut in the right place then JB the plate to the rail. When hard remove bolt and use it to hold up the tray.

 

Isn't a simple solution to use larger tapping screws?

 

That works until the hole gets bigger than available larger sizes of self tapping screws. - Biggest available in the metric world tend to be 6.3mm shank diameter - roof sheeting screws. When they pull out you can then use an M8 tap but that doesn't work to well either.

 

Blind Rivet Nuts solve this problem beautifully and permanently....
I'd not seen them until a few years ago when we started using them at work, and
if you'd not heard of them, you might want to check them out....
Here's a linky, but the tool and rivets are available at Grainger and other tool supply houses too...
http://www.emhart.com/products/pop/popnut.asp
They install just like a pop rivet, except the rivet gun screws into the rivet nut before and after it's installed,.... The video on the linked
site shows this if you pay close attention.....

Oops, ..... Just saw Jon suggested this in frame 3 already..... Oh well, I'll leave the post for the linky if nothing else.....

 

I've used a metric tap & die set to thread larger holes into the frame rails, which seem to be the only one's I've had problems with. Then use metric bolts to fasten. I do have a mismatched set of bolts though.

 

Nicole wrote: "This reminds me of the car I recently saw on the side of the freeway. The hood had opened at hiway speed, flipped up against the windshield and the part higher than the windshield flipped back, hitting the roof very hard. Needless to say the car was a total loss... no, it wasn't a 928, but a good example of what the power of wind can do. I'm glad you got away with only the damage you describe!"


BTDT X 2.

1st in XK150 at 100plus. I was a passenger and I'm glad the top was up. It bent the bows far enough that my Dad and I couldn't see each other's eyes.

2nd in 356B Roadster at 60 or so. Somewhat less damatic but not much. I was driving that time.

Both instances were caused by letting a gas station attendant close the hood. Not again in the forty plus years since.

 

I modified the rear pan on my 90' S4, so that it can be removed while the two aluminum front side brackets remain on the car.

So to remove the rear pan, I only need to remove the screws going into speed nuts. Saves wear and tear on the self tapping screws into the chassis.

For this mod, I just drilled thru the spot welds that hold the brackets to the pan, then cut two slots (each side) for speed nuts to slip into. Used the same Porsche screws and speed nuts as elsewhere on the pan. Very easy mod.

 

Had this happen to me the 1st month of owning the '88. It was 5:30am, very dark on a street with no lights. I think I might have left a stain in my shorts.

 

Rob,

Both trays on my car are held up with nutserts. I have the tool and the inserts, albeit only in SAE threads. I have 10-32 throughout, except for the tinnerman nuts in the pseudo NACA ducts at the steering rack in the front pan. You are welcome to the tool and the inserts you need, of course. The inserts allow you to use lockwashers successfully.

 

Bob-

Ha, I was just looking at the blind rivet nut webpage.... I would love to put a pair of nutserts into the frame rails, those holes are pretty far gone. Yet another reason to find an excuse to come to Glendale!

 

Rob--

I plan to visit 928 Int'l Monday or Tuesday for some bits, and also will get the new windshield installed if Michelle's delivery stars are aligned correctly. Something about harmonica virgins. Anyway. if your patients can give you a break, I can either drop the kit to your house/office/whatever, or meet you at some other convenient place for lunch and a tool transfer.

Let me know!

 

Well, I finally got 3 hours of bachelordom, so I nutserted the belly pan holes. Dr. Bob kindly lent me his nutsert kit a few weeks ago. For those of you not familiar with them (I wasn't), they're sized for the O.D. of the hole you're drilling out to fit them. The stripped hole in the frame rail was just under 1/4", so I drilled it out with a 1/4" bit and loaded an 8-32 nutsert on the tool:



For a given size nusert, you screw the nutsert onto a hexhead bolt which runs through the ~1/2" nut, which in turn fits onto a corresponding allen socket inside the barrel of the tool. The knurled black collar on the tool rotates to lock the assembly together.



Then you just place the nutsert in the hole, and turn the T-handle clockwise, forcing the hexhead bolt through the nutsert and expanding it in the hole. Then just unscrew the T-handle and you're done. Voila:

 

They are also available in metric sizes. I've installed them in my aluminum belly pan.

Jim mayzurk
93 GTS 5-spd