Author Topic: RIVNUTS (Read 2879 times)

MalteseFalcon · « **on:** January 18, 2007, 10:56:29 PM »

A while back on TAC we had a discussion about the rivnuts that the bolts that hold the front sway bar mounts thread into. These often freeze up, creating a problem. Mine were stuck, but my subfame frame was also bent, so I ended up replacing it with one from a Camaro.

Only problem is that Camaros didn't get rivnuts - only the cars with the 1.25 inch front sway bar got them. I got a VSE front sway bar, and it came with rivnuts and the information that if your car wasn't a Trans Am having the rivnuts, you had to install them because threads in the subframe weren't strong enough.

We've talked about different ways of installing them, and I've looked for tools, but I finally found this:

http://www.hansonrivet.com/w69.htm

I saw a similar unit pictured in an article about installing a Fire Am package where the work was being done in VSE's shop. Price is $50.15. They only do one size of rivnut. The part number for one that does the 3/8 coarse threaded rivnuts used in our cars is L722-3716. I've ordered one.

LeighP · « **Reply #1 on:** January 19, 2007, 08:49:12 AM »

Did you consider simply drilling and tapping threads into a 1/4" to 5/16" thick piece of plate steel with two holes, then sliding it into the end of the subframe above the holes for the sway bar saddles? Tack weld the end of it to hold it in place while you feed the bolts in when fitting the sway bar.
Just an idea.

MalteseFalcon · « **Reply #2 on:** January 19, 2007, 11:09:16 PM »

Quote from: "LeighP"

Did you consider simply drilling and tapping threads into a 1/4" to 5/16" thick piece of plate steel with two holes, then sliding it into the end of the subframe above the holes for the sway bar saddles? Tack weld the end of it to hold it in place while you feed the bolts in when fitting the sway bar.
Just an idea.

That would probably work, although I just checked the rivnuts that came with the kit and they provide about 5/8 to 11/16 of thread engagement - I suppose you would have to have a simlar thickness of metal plates to get the same grip?

thumper78 · « **Reply #3 on:** January 19, 2007, 11:47:12 PM »

Quote from: "MalteseFalcon"

That would probably work, although I just checked the rivnuts that came with the kit and they provide about 5/8 to 11/16 of thread engagement - I suppose you would have to have a simlar thickness of metal plates to get the same grip?

I think that grip and strenght doesn't improve once the length is equal to the diameter of the fastener. i.e. 3/8" length for a 3/8" diameter bolt, 1/2" length for a 1/2" diameter bolt .

But extra length for a bolt does make one feel all warm and fuzzy and safer. Just not necessary from an engineering standpoint.

LeighP · « **Reply #4 on:** January 20, 2007, 07:16:20 AM »

Yep...aircraft hardware (nuts) are rarely larger in length than the diameter of the bolt.
Another idea would be to weld a couple of high tensile nuts onto the back of a thinner piece of stock (say 1/16" or 1/8") then slip that into the chassis and tack it to the front of the rail.....probably easier to do than the drilling and tapping a thicker piece of stock.

DWills · « **Reply #5 on:** January 20, 2007, 07:59:01 AM »

Just an aside from a mechanical engineer; the first three threads no mater the dimater of the fastener take 90% of the load, and additional threads after that provide less and less load capability.

RENOVATIONS · « **Reply #6 on:** January 20, 2007, 09:14:40 AM »

Quote from: "LeighP"

Yep...aircraft hardware (nuts) are rarely larger in length than the diameter of the bolt.
Another idea would be to weld a couple of high tensile nuts onto the back of a thinner piece of stock (say 1/16" or 1/8") then slip that into the chassis and tack it to the front of the rail.....probably easier to do than the drilling and tapping a thicker piece of stock.

That's a good idea I hadn't thought of. The attachment point for the sway bar mounts seems to be a common problem. I may be able to use this to save my sub frame, if I can also repair the body mount "tabs". I bought a parts car hoping to use it's sub but come to find one of the "horns" was bent once I got the front sheet metal off. :? Good save, thanks guys.

LeighP · « **Reply #7 on:** January 20, 2007, 12:35:29 PM »

You're welcome....I've seen "nut plates" used in lots of applications over the years. I'm surprised Pontiac didn't use them for the engine mount bolts instead of individual nuts.....those nuts are annoying to get hold of when changing engine mounts.

MalteseFalcon · « **Reply #8 on:** January 20, 2007, 02:04:45 PM »

Interesting. I would assume that the reason Pontiac used them was the speed with which they could be installed, then.