[glhs#116]

So.. Continuing the pain in the arse theme..

On a second gen there are two brackets on the front subframe that hold the central part of the front antiroll bar. This last weekend I finally went to replace the bushings. Well, one of the three bolts never came out. It loosened for a bit then just spun. I continued and got the bushings changed but, of course, that one doesn’t stay in now. Probably because it is impossible to fully tighten the bolt that just spins. Mine is a 71 and the bolts fit a 8mm Allen key (maybe it’s 5/16 or whatever but 8mm is a good fit).

So I am sure I am not the first. I guess I have to try to get ahold of the captive nut inside the subframe. It’s on the steering box side also of course. What’s my path to getting to that nut without taking half the front end off? Also, if you remember, what’s the nut? 9/16?

I can’t leave it. There are no straight roads here and speeds are somewhat high. I really can’t afford for the front handling to suddenly change dramatically without my knowledge.

Sam

[25stevem]

That’s a true 300% pain in the Ass issue!

I had that happen on a 68 A body I had ages ago.

My buddy could weld very well so what we did was use a circular hole saw I little bigger then the nut to cut out that section of the frame rail.

Note that for these saws to work the center bit needs to be bigger then the hole in the frame for the bolt.

This can be a problem so you might just have to grind a section out .

If you have a high speed grinder and a worn down cutting disc that is now a small diameter that can work well also .

We then got a big thick washer and this time a stainless fine thread nut.

He welded the nut to the washer and then he welded the washer to the frame.

Once we had the parts and the hole saw in hand the whole repair took less then 1 hour.

Another solution if you are not concerned with show quality looks is to drill thru the top of that frame section and just use a really long bolt or a threaded rod.

Let us know how you make out.

[sdbob]

I'd use a dremel with a cutter, slice nut out.Its a pain. Slice,chisel. I've used a steel plate and welded 2 nuts to it appropriate distance apart,with holes,then slid into frame.

[DOC]

Is the frame thick enough to tap and just thread the bolt into the frame instead of a nut on the backside?

[25stevem]

To the above question, unfortunately no!

[Formulas]

i have 1970 birds and they are just bolts threaded into the frame 3/8-16 threads

sometimes the bolts will get cockeyed without you knowing it due to the spread of the bar clamp and crossthread will result

last time i had my sub frame completely apart i ran allen head bolts down from top with loctite essentialy studing them

one of the bolt holes is real close to the inner wall of the frame i believe the thought of simply putting a nut in there or regular bolt may be problematic depending on which location

a good welder could plug weld it grind it flush and you re'tap it

[78w72]

Originally Posted by DOC

Is the frame thick enough to tap and just thread the bolt into the frame instead of a nut on the backside?

Originally Posted by 25stevem

To the above question, unfortunately no!

the frame is thick enough to tap! thats how they did it on later year 2nd gens, my 81 is like that. granted its not thick enough to allow high torque on the bolt but the spec'd torque for the sway bar bolts will work ok.

i have dealt with this a couple times on 2nd gens, just recently on the 81 where a prev owner over tightened one of the bolts & it stripped out the threads in the frame. the best/easiest solution for this is whats called a rivnut or nutsert, a small threaded piece of metal that you insert into the hole & use a small tool to pull it down inside the frame like a rivet which expands the inside part & locks it in & allows to keep the original size bolt with plenty of threads for most purposes. i bought some of the 3/8 rivnuts from fastenal for a couple bucks... but since the hole needs drilled out bigger for the rivnut i decided to just tap one size bigger for now. there is about 3 threads worth of thickness to the frame which should be ok for this purpose if its not overtightened, mine is doing fine with poly bushings. if you use oil or anti seize be careful because that increases the torque on bolts.

on a 78 t/a i had that did have the nuts inside the frame that can spin free or break, i had a friend weld it, there are 2 big holes on each side of a 2nd gen frames that will just barely allow a curved wrench or tip of a welder to get inside the frame, it was tricky but he did it without too much trouble & it lasted for many years of hard driving taking corners to the max ability of the tires/suspension.

if you dont want to drill out or remove the factory nut see if someone can weld it, or try & get a wrench in there to hold it. it is a 9/16 head 3/8 course thread bolt for the sway bar brackets.

[GTO TEX]

I've had this happen on my A body and F body. Grind off old fastener and knock out of the frame. Drill out the hole to 1/2" and install a 3/8-16 steel nutzert. You won't ever have to worry about it again.

[78w72]

Originally Posted by GTO TEX

I've had this happen on my A body and F body. Grind off old fastener and knock out of the frame. Drill out the hole to 1/2" and install a 3/8-16 steel nutzert. You won't ever have to worry about it again.

yep, thats what i called a rivnut, but drilling a 1/2" hole seemed excessive, was much easier to tap one size bigger threads for now using the existing 3/8 hole... if that gives out then i will use the nutsert.

but if the factory nut threads are still ok, he should be able to weld it through the 2 big holes in the side of a 2nd gen frame... seems like they were put there to allow access to these bolts.

[NeighborsComplaint]

The Riv-nuts work fine as long as you are willing to go "all-in" and enlarge the hole to accept it or have access a to a welder to tack it and grind flush if it turns. Also, if the metal is too thin to drill and tap, there's an option called a trailer hitch bolt fishtape.

You ream your 3/8" hole slightly for an easy slip fit, push the fishtape coil end up through from the bottom and push it out of the subframe, thread your bolt into the coil and pull it back through, remove the coil and then install a nut. It's backwards (bolt inside frame and nut exposed) but it's really easy. While you can't access the bolt head inside the channel it will tighten down easily with a ratchet and some lube on the threads. I used one on 70's - 80's crash bumpers to install the hitch bar support to the back of the bumpers in my snowmobiling days.

You can also have someone tack a short length of bar to the bolt head that will keep it from turning inside if you're concerned. They used to sell bolts with an "ear" already tacked to the bolt head for this purpose. They're discontinue because they proved unnecessary when working with brand new nuts and bolts that thread together easily.

[Tom Vaught]

I have used the Nutserts in my 64 frames with no issues for many years.
Ever since Ken Crocie sent me his large front sway bar many years ago.

Once a Nutsert was installed properly, I have NEVER had an issue with the nutsert coming loose in the frame.

Don't plan on ever selling the car so if it has a strong mounting point for the sway bar, that is what matters.

Tom V.

[glhs#116]

I'm so grateful for all the help. I wanted to keep it all inch sized but just too big a hassle from here so I have some "M10" cap screws coming. The head will take a 8mm Allen key (which is pretty much same as 5/16"). The shank will be 10mm (the 3/8" shank on the stock cap screws are around 9.5mm). So I won't lose too much sleep about bastardising things. Hey! I had an 80s Dodge so I know the hell of a car that is half inch and half metric! With that I ordered M10 nut rivets. I could have gotten inch sized bolts OK. But inch sized rivet nuts were going to be the difficult part. Especially with the correct sized insert tool.

So, I am pretty hopeful. I'll post back with how I get on.

Sam

[glhs#116]

Well, just for posterity and those that find this on search, it looks like that was a good call on the rivet nuts.

I got M10 x 25mm hex cap screws as the closest metric match I could find. Takes an 8mm Allen key which is pretty much the same as 5/16". Bolt is 10mm diameter whereas the 3/8" factory ones work out to around 9.6mm so pretty close. They look fairly similar


The M10 nut rivets want a 13mm hole. Well, turns out the factory frame holes are 1/2" so, again, pretty much spot on.


In the end I had to replace three of the four. It was a good feeling to get them all snugged down and know that this should hold for a while now.




Thanks for all the help, everybody!

Sam

[25stevem]

Sam, good to hear that one of the many possible fixes worked out for you.

Now take all those bolts out and add some anti seize my friend, lol!

[Tom Vaught]

Originally Posted by glhs#116

Well, just for posterity and those that find this on search, it looks like that was a good call on the rivet nuts.

Thanks for all the help, everybody!

Sam

That "fix" has worked for me for 30+ years. Glad you installed the right parts and the great pictures will help others understand the installation process.

Tom Vaught