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Was going to replace the front sway bar bracket bushings. Noticed that the two bolts holding each bracket are just self-tapping bolts and the thread into the frame with just 2 threads engaged. The frame thickness just allows about 2 maybe 2.5 threads of engagement with the bolt. Not the best design and the threads can easily strip out with such minimal thread engagement.
There are some holes in the side of the passenger side frame that would allow for running a washer & nut on the opposite of the bolt but it would be difficult getting a socket in the frame but appears doable. The drivers side does not due to the steering box.
I replaced the front stabilizer bushings on my 1971 CS. I recall the screws and they appear identical to the image you posted - self-tapping (5/16" I think ?). It's possible someone previously stripped the screw threads &/or the self-tapping hole has been stripped (enlarged). It's also possible a PO may have replaced the bushing brackets &/or the stabilizer with the incorrect (or oversize?) front stabilizer requiring a differently sized bracket but used incorrect screws? The 1972 PIM demonstrates P/N 9431970 (20 - 28 lb-ft torque), but I can't find the exact size of these screws. Since they are self-tapping screws, I would "suspect" if the threads are stripped in the holes or the screws you could use oversized self-tapping screws since they're "self-tapping". Just a thought anyway.
I have replaced those bushings on my Vista and convertible. They were no problem. Are yours stripped? If not I would just put 'em in. Seems most of the force on the sway bar would be pushing up against the frame??? But if you can get a nut inside- sure why not if yours are stripped.
The self-tapping bolts are stock and are fine for factory parts. If you are going larger/stiffer than factory, the start to become questionable. The best solution is nutserts in the frame. If you think you have access, separate nuts and bolts will work, but are a PITA to install and remove.
The biggest problem with the self-tapping factory bolt is that thread engagement is only 2 threads into the frame. If there was more thread engagement, then it wouldn't really be a problem. Who was the engineer who decided that 2 threads of engagement is enough to hold a sway bar on a 3,800 LB car?
The passenger side front one did strip out while trying to reinstall it. I ended up going with a threaded bolt, washer and nut. I ran a swivel extension through the frame with a deep socket and was able to clamp it down nice and tight. Hopefully never have to remove it again.
My worry is the drivers side. They are holding for now but if I remove them to replace the bushing, I fear one will strip like the passenger side. On the drivers side you cannot access inside the frame due to the steering gear box being in the way. Only solution would be to get the next sized up bolt and retap it but the problem still exits. Only 2 threads of engagement on the frame.
The self-tapping bolts are stock and are fine for factory parts. If you are going larger/stiffer than factory, the start to become questionable. The best solution is nutserts in the frame. If you think you have access, separate nuts and bolts will work, but are a PITA to install and remove.
The self-tapping bolts are stock and are fine for factory parts. If you are going larger/stiffer than factory, the start to become questionable. The best solution is nutserts in the frame. If you think you have access, separate nuts and bolts will work, but are a PITA to install and remove.
My sons Acura had the threads pull out of the unibody for the rear sway bar mount. It is a blind hole with no access. I ended up cutting down a speed nut and enlarging the hole enough to insert the threaded portion into and welded it in place. Then i ground it down as flat as i could without removing all the weld and bolted it in place. 5 years and it is still holding.
The biggest problem with the self-tapping factory bolt is that thread engagement is only 2 threads into the frame.
If you have a look at those holes you'll see that they are pierced and not drilled. Piercing folds the steel over at the sides of the hole which facilitates the threads of the screw. IMHO they did this because it was the least expensive most effective way due to lack of access to the back side. I always torque them to spec and if it works it will likely be fine, if not you have to use a nut on the back side or weld up the hole.
The factory also changed these over the years. The older A bodies used a smaller diameter screw, and if they strip out you can use the later model larger diameter screw.
