Frame Stiffening

[Rrod]

Restoring an original 70 Challenger R/T 383 4-speed car. Car is a rolling shell at this time. Currently repairing needed sheet metal work. Adding rear torque boxes. Already has front toque boxes from day one of manufacture. Engine will be a 440 6pak but beyond stock hp.  Deciding on whether to add US Car Tool longitudinal frame stiffeners to tie the front and rear torque box sections together. This is the time if I'm going to do this since it is a rolling shell. I'm totally fine with adding the rear torque boxes. My question is will adding the weld in frame stiffeners make any improvements in suspension quality and will it lower the value of the car?  The vehicle will be a street cruiser but see occasional 1/4 mile duty (Muscle Car Shootout events). Thanks.

[anlauto]

They help stiffen the car if you want a stiff car, but they don't help the value whatsoever in my opinion

[Filthy Filbert]

They help stiffen the car if you want a stiff car, but they don't help the value whatsoever in my opinion

are you saying they don't raise the value, or are you saying they WILL lower the value, or are you saying they are value neutral and the rest of the car is what will determine value?

[anlauto]

They help stiffen the car if you want a stiff car, but they don't help the value whatsoever in my opinion

are you saying they don't raise the value, or are you saying they WILL lower the value, or are you saying they are value neutral and the rest of the car is what will determine value?

Sure.....I guess it depends on the buyer...personally I don't like them, so it would detract value of the original car in my opinion, but if the buyer wants the same thing the original poster wants, then maybe he would pay more  these cars never had them from the factory, so I really don't see the need for them with basic street driving, and maybe to add time on a track 

[Filthy Filbert]

Well, on an originality type resto, I see your point.   But, this guy isn't doing that.   He's changing the engine, he's adding lots of power, and obviously doesn't care about originality.

Different strokes...keeps the hobby interesting.

There's definitely a benefit,  These cars may not have had them from the factory, but look at how much big power cars twist on launch with sticky tires.   Same with cornering.   Usually the guys who want to add these are not interested in casual cruising through the downtown strip, and plan to push their cars a little harder than most.

[anlauto]

  To each their own 

[MoparLeo]

Another option would be bolt on stiffeners. Better than nothing and much easier to return to stock.

[Mr Cuda]

I'm all for through the floor subframe connectors and every available weld in brace made.
Obviously,  some cars are too "valuable " to modify.
My experience is that once stiffened,  the car ride like a Cadillac, with none of that unibody quiver from stiff suspension.
I have larger 1" plus torsionbars, aftermarket sway bars, and big shocks. Of course it needs to be over 60 mph to be smooth,  but the chassis feels great. Stiff like a new car.
Prior to the subframe connectors,  the  standard 440 suspension wad strong enough to flex the car. Afterwards,  the suspension had to do its job. Immediately,  the factory. 92 torsion bars were exposed as being too weak.


I guess I  should add, that the mopar performance "bible" advocated  chassis stiffening.  They pointed out that the average general motors car had an effective spring rate of 300 lbs per inch.
The base mopar torsion bar was as low as 120lbs, with the rear at 250-280.
Now torsion bars suck up the load differently than  coils, but maybe the engineers knew something.
I hate to be critical of my favorite car, but having done heavy  collision for years, the newer car chassis stiffness is impressive.

[usraptor]

If you do decide to add them, now may not be the best time.  Per instructions I have read (I'm considering them) they say the car and suspension should be "loaded" and sitting on it's tires and wheels before installation.   

[HP2]

Moat cruisers don't need them, but they do help shore up chassis movement and make panels gaps, window sealing, suspension all work better in addition to reducing squeaks and ratttles.

If you  race with any regularity, they help even more.

They aren't  always viewed positively by the restoration crowd. However, if returning to stock is a concern,  use the bolt in style and weld the ends. This firms things u considerably and can easily be cut out of desired. The full length weld inversions  would be very, very difficult to remove.

If you do decide to add them, now may not be the best time.  Per instructions I have read (I'm considering them) they say the car and suspension should be "loaded" and sitting on it's tires and wheels before installation.   

This is only important if you car is painted and assembled with consistent panels gaps. If it is under construction, it isn't important as you will be setting all these dimensions as you put it back together.

[jimynick]

"This is only important if you car is painted and assembled with consistent panels gaps. If it is under construction, it isn't important as you will be setting all these dimensions as you put it back together."

Firstly, who would embark on installing SFCs on a finished car? As for the suspension being loaded just raise the car and set it on safe supports to load it. Personally, I put my conformal weld-ins in on the rotisserie and had no issues. Due to the nature of these cars being built in a lousy fashion, you may find that your range of adjustment is no where near what you need/want when it comes time to fit the car up. Just support it evenly and you should be good to go. Good luck 

[dodj]

They will help with street handling and will make an immense difference at the track. I had a friend who thought he wouldn't need them for his warmed up 383. After a day at the track the doors didn't close like they used to.
It also quiets the car down a bit from squeaks and rattles. If you are doing 100% resto..don't do it. ANY other variation will benefit from stiffening. I'd do a QA1 k-member too. It also makes a big difference.
The term flexi-flyer applies to these cars that are still original unibody.

[Brads70]

IMO it's almost a must do unless it's a rare collectable. If you want to enjoy driving it and upgrade from the poor handling when they were built. No point in adding bigger torsion bars unless you do, as the whole chassis is a big torsion bar. Then factor in 50 plus years of metal fatigue etc... why wouldn't you is more the question. 

[HP2]

"This is only important if you car is painted and assembled with consistent panels gaps. If it is under construction, it isn't important as you will be setting all these dimensions as you put it back together."

Firstly, who would embark on installing SFCs on a finished car? As for the suspension being loaded just raise the car and set it on safe supports to load it. Personally, I put my conformal weld-ins in on the rotisserie and had no issues. Due to the nature of these cars being built in a lousy fashion, you may find that your range of adjustment is no where near what you need/want when it comes time to fit the car up. Just support it evenly and you should be good to go. Good luck 

Someone who bought a finished car, that doesn't have them, but they want to improve their car. Happens all the time.

[ZippyZoo]

Go for it!  Now is the perfect time.

Even while it was still "young", my '71 vert was to the point that if I jacked it up with the doors closed, they would pinch the top of the rear quarters and you couldn't open them.  If you jacked it up with the doors open, there was no way they would close.

This last go around, I had the USCT frame connectors welded in.  I just got the car back from the body/paint shop and am in the process of putting it all back together, so it's gonna be a while until I can actually get it out on the road and feel any difference in handling.