[123rmp]

I have a 73 Rally Challenger (70 clone now). I rebuilt my entire front end with new PST rebuild kit. Used the stock rubber lower control arm bushings. Got new Just Suspension 1" torsion bars.

With my engine out per all instructions everywhere I read, I left the LCA pivot shaft nut relatively loose so that the shaft can turn and will tighten when the full weight is on it. I have read the same thing applies to the upper control arm cam nuts but that is not as widely documented. Anyway......to the specific topic installing torsion bars.

After all of the other ront end was rebuilt, I loosened the torsion adjuster all the way, set the torsion bar adjuster arm all the way down, removed the frame bumper for the upper control arm, pulled down on it, etc and the new torsion bars slipped right in.

Is there any problem with having done this with the LCA loose? Or, any issue in the way I did this? for example, will I have to put the engine in, tighten the LCA pivot bolt, then remove the torsion bars and reinstall? Clearly I don't want to ruin the LCA bushings, have the front end sit too low or too high, or have other bad result after all the hard work.

This is the first time I have done this and just need some reassurance I am not going to hurt myself.

Your advice appreciated guys.

[Adrian Worman]

Why did you remove the engine to change torsion bars?
Do it with the car on a ramp or on axle stands and it should be a piece of cake, even much thicker bars than you have installed will clear every thing.
I'm not sure I understand what your problem is

[dave-r]

You are doing OK. But I also don't understand why you removed the engine.

I think I read that you need to tighten the LCA nut with the weight on the wheels. But from memory the LCA rotates freely around the shaft even when it is tightened. So I don't see the need unless I remember wrong.

You will need to adjust the UCA bushes to align the front end anyway.

Just bolt it all together and don't take notice of the crap stuff you read on the internet. 90% of it is written by 20 year olds that have never lifted a spanner in their lives.

[burdar]

If you tighten the LCA before the car is at the correct ride height, you can damage the bushing. The same goes for the UCA's. Just set your ride height and tighten the nuts. Then have it alighned.

[123rmp]

Engine is out for other purposes (smoking on decelleration - bad rings apparently as the shop went thru heads, etc). Anyway, I decided to redo the front end while I waited on the machine shop to finish my engine......so no did not remove the engine because of the front end rebuild. I am also putting a new roof skin on the car while the engine is out...

Still waiting on engine but I'm not ready for it yet. I am going to repaint the engine bay too while it's out as I had a Master Cylinder leak and ruin the firewall/inner fender paint.

My 2 cents is that once you tighten down on the LCA Pivot Arm bolt the pivor arm is fixed. I THINK the LCA moves, twisting the rubber bushing, but he pivot is fixed tight. If you tighten before car is at natural, with full weight, ride height it breaks the LCA bushing quickly when the weight comes on it...the rubber bushing is under stress all the time while the car sits, not just when you make the supension go up and down - that is my deduction having sat for three weekends staring at it and envisioning how it all works together.

[burdar]

That is correct. By tightening the LCA when the car is at the correct ride height, the bushing is in the neutral possition. Then it just has to flex a small amount in either dirrection. If the LCA is tightened with the suspension hanging, it's under load and really has to flex a lot when the suspention is at its highest point. The bushing will tear.

The UCA is the same way. With the cam bolts tight, the outer bushing shell is held tight. The rubber then flexes. They can tear if you tighten the cam bolts with the suspension hanging.

[123rmp]

By the way, a couple pics of the car progress. Did not take any of the suspension but here is the roof work....

Off it comes

Rust coating

Welded back on

[dave-r]

Nice job on the roof.

I am sure the suspension movement does not twist the rubber bush. Otherwise it would fail within a few miles.
The bush holds the arm on the pin. But the bush is inside a sleeve that the arm rotates around. There should be no rotation force on the bush. Otherwise the rubber would tear the first bump you went over.

My brain is pretty screwed up but I am sure i remember it that way. Without the torsion bar in place the LCA should be free to rotate even after the shaft is tight in the K-frame.

[123rmp]

You may be right.

Honestly I don't know if the whole LCA pivot shaft does rotate or not. Looking at how it goes together, I would have bet you it does not, but I could definitely be wrong. I get proven wrong quite often (I'm now married over 30 years so it's a daily event and keeps the peace).

Never thought about how the LCA works until I got into the rebuild. I do know the torque specs are like 160 lb/ft on that nut and the pivot shaft quickly gets pretty stiff with the slightest tightening (acknowledged that that is not with weight on it). These things do behave very different in real operation, with full car weight on them. I do know that the torsion bar allows for up/down movement by converting the up/down to a rotational movement which it resists. The torsion bar socket as you know rotates free within the LCA, other than as restricted by the adjusting bolt.

You are right that the rubber LCA bushing is very stiff and it can't move much if it does, which is why it breaks if the LCA is not set at a neutral point. It does have some movement or vibration isolation purpose, otherwise why make it rubber and a point of failure, right?

I am sure some smart guy on here will post the proof one way or another..... and you may be right.

Regardless, I am happy you guys have confirmed three basic things
1) tighten LCA bolt after weight on suspension (regardless if the pivot actually "pivots")
2) tighten UCA cam nuts after weight on suspension and it's aligned
3) I have installed the torsion bars correctly

Thanks!

[dave-r]

But if the LCA rotates freely around the pivot it can't have a neutral point? Unless that free travel is limited at some point. Which I was sure it wasn't?

It's been too many years since I did mine. But no harm in being safe and it is easy to access the nuts once the engine is in and the car sat on the ground.

[burdar]

Someone posted the replacement procedure in the FSM on another site. The factory said to not tighten the LCA nut until the car was at ride height or the bushing could be damaged. Like you said, it can't hurt.

Tightening the LCA and UCA nuts is the last thing I'm going to do before driving the car to the alighnment shop. I also waited to tighten the front leaf spring eye bolt until the car was on its wheels.

[Adrian Worman]

Burdar is dead right on the sequence for tightening that lca shaft nut but the lca should still move up and down fairly freely without any spring tension applied to it.
Remember when you do a top ball joint or similar work you don't have to slacken that nut off to be able to push the lca thru quite a wide arc. The uca and lca bushes have sleeves so that the relevant shafts can rotate inside then without binding and the lca shaft has a stop on it to prevent the nut from trying to draw it thru the K member register and crush the bushing.
I wouldn't worry too much about it if you've followed factory procedure......... and enjoy your new stiff bars, car will handle much nicer