Factory Rear Sway Bars

[70 Challenger Lover]

I know, another rear sway bar question. In my searches, I find discussions on end links and bushings but it seems everyone prefers to weld the bushing straps back down to the frame rail brackets.

This makes sense since the bracket snugs up to the rail and has no room for thick bolt heads.

Has anyone tried using a short carriage bolt rather than welding? If the bolt head was on the inside, there wouldn't be much gap between the bracket and the frame rail. I'm not sure if the forces involved require the bracket to be up against the rail but there's also forces trying to pull the bracket away as well.

I'll weld if I must but I liked the idea of being able to remove it easily later on. I want to try rubber vs poly and can't do this if I weld.

[EV2RTSE]

That's how Firm Feel sells their rear sway bar kits, with bolt-in bushings.
https://firmfeel.com/collections/rear-sway-bar-kits/products/70-74-e-body-rear-sway-bar-7-8

Here's someone else's car and a slightly different approach-

[70 Challenger Lover]

Perfect. That's how I'll do mine.

Thanks for the link on FirmFeels piece. Didn't know they offered one in the same style as factory. I like the thicker bar too. Might have use theirs on my next build rather than hunt down old factory stuff that's in rough shape.

[torredcuda]

Call Firm Feel, I ordered thier 1 1/8" front bar and was going to order a larger rear as well but the guy told me it would handle better with the stock 3/4" one.

[70 Challenger Lover]

Call Firm Feel, I ordered thier 1 1/8" front bar and was going to order a larger rear as well but the guy told me it would handle better with the stock 3/4" one.

This particular 3/4" factory original bar is going on my 71 Barracuda ragtop. I put in a nice 340 / four speed and the next step in its conversion is to receive 340 brakes and suspension all around. Trying to keep it fairly close to factory correct appearances.

On my 318 powered 71 Barracuda hardtop, I added a factory 7/8" front sway bar only when I rebuilt the suspension and everyone said I wouldn't notice any improvement. It won't win road races carving through the corners but I immediately felt a significant improvement in how much less it rolled in cornering.

On my other e bodies, I'll probably experiment with more aftermarket stuff until I figure out what I like most.

[HP2]

Call Firm Feel, I ordered thier 1 1/8" front bar and was going to order a larger rear as well but the guy told me it would handle better with the stock 3/4" one.

That's because Mopars are already over-sprung on the rear with the factory spring set. Going too large on a rear sway bar will make them even more tail happy, unless you also step up the torsion bars a few steps to offset the rear spring rates.

[70 Challenger Lover]

Call Firm Feel, I ordered thier 1 1/8" front bar and was going to order a larger rear as well but the guy told me it would handle better with the stock 3/4" one.

That's because Mopars are already over-sprung on the rear with the factory spring set. Going too large on a rear sway bar will make them even more tail happy, unless you also step up the torsion bars a few steps to offset the rear spring rates.

So if I were seeking out a more balanced suspension, what would you recommend? My 318 car has the wimpy 318 springs out back. They function fine but I believe the rate is somewhere around 90. I see Eaton offers a 115 rate which I was planning upgrade to. It's a 340 car now so I'm seeking slightly sportier handling.

The front 318 torsion bars will soon be swapped for 340/383 bars (778-779) and I'll add a small factory front sway.

I guess my question is how to determine when the car's suspension is balanced front to rear.

[HP2]

Exact balance is often a personal preference, but there is a range that will get you close and you can improve over the factory set-up.

In the book "B Body Performance Upgrades" by Andy Finkbeiner, he recommends a front spring rate that is 10% of the front weight of the car. In his example, a 3500# car with 1800# on the nose should use a 180# wheel rate. That would be roughly a 1" diameter torsion bar matched to the OEM XHD spring pack in the rear. Those leaf springs are around 140-160# rate.

The Hotchkis and XV efforts used a slightly smaller t-bar. They never published the size but based on info I've seen around, the web these are in the .94-.96 range.  They both also suggested lower rate rear springs, again proprietary, but looking at various specs around the web, they are around 120-140# rates.

If you plan on using the 340/383 bars, I believe these are around .88 in diameter. (sorry, don't have my chassis book in front of me at the moment), they should be a decent match to your 318 leafs. The factory front sway bar will help with cornering.  You could step this sway bar up a bit more to a 1" for a bit more lateral holding power. If you add a factory sized rear bar, then I'd suggest a 1.125 front sway bar.

On the rear, the factory used a .75" bar.  This bar mounted to the frame and attached to the axle via links. It had very short arms from the bar to the links. Maybe about 10" or so. These shorter arms apply more bar force to the axle.  I bring this up because a lot of aftermarket bars are 1) larger in diameter, 2) hung from the axle, and 3) have much longer arms.  However, in applied rate, they are very similar to the factory bars despite having a much larger diameter. The 1+ of these bars does not get as much of their rate when applied because of the significantly longer attaching arms, which can be 20 or more inches in length.

Suspension is all about the geometry, both in how it works and how rates are applied.

[Mr Cuda]

 Herb Adams,  noted  gm f body racer and parts seller. Often a guest writer/contributor for Hot Rod once said,  "I  have never seen a front bar too big".
  Being a convertible,  you need to not go overboard  with spring rates.  Chassis flex is real. Even subframe  connectors and chassis bracing will not get rid of cowl shake if you overspring.
 318 rear leafs, with .890 front bars.  Stock rear bar , aftermarket front 1 1/8.
 A strong support up front with a supple rear would be best.

Add an edit.
Depending on ride height,  the. 890 bars could be too soft.
 Torsion bar spring rate is calculated with the  lower arm and travel.  Rate builds progressively.  No travel,  no rate.
 I put 318 .860 bars in a 440 car and had to crank the adjuster all the way to get ride height.
The problem with this is when the car leans,  the inner bar is trying to unload its massive tension, and adds to the lean.  For a drag race launch, it helps lift.
This was for a highway flier, so to control lean, I have 2 front sway bars.

[Brads70]

Call Firm Feel, I ordered thier 1 1/8" front bar and was going to order a larger rear as well but the guy told me it would handle better with the stock 3/4" one.

That's because Mopars are already over-sprung on the rear with the factory spring set. Going too large on a rear sway bar will make them even more tail happy, unless you also step up the torsion bars a few steps to offset the rear spring rates.

So if I were seeking out a more balanced suspension, what would you recommend? My 318 car has the wimpy 318 springs out back. They function fine but I believe the rate is somewhere around 90. I see Eaton offers a 115 rate which I was planning upgrade to. It's a 340 car now so I'm seeking slightly sportier handling.

The front 318 torsion bars will soon be swapped for 340/383 bars (778-779) and I'll add a small factory front sway.

I guess my question is how to determine when the car's suspension is balanced front to rear.

I assume you have a convertible by your avatar? If so I'd stick close to stock, as the whole car will end up being a torsion bar without the strength of a roof. The chassis will flex lots in stock configuration. If your not to concerned about keeping it original , first thing I would do would be adding subframe connectors and torque boxes.Last part I would add would be the rear sway bar for handling improvements.  But being a convertible I assume you want to leave it as stock as possible.
I'd suggest good shocks first, double adjustable if money permits. I have the QA1 shocks on mine for over 10 years and am happy with them. 

[RUNCHARGER]

Yup: I remember the handling of my stock, 71, 383 R/T. 383 in front, .88 bars, rear sway bar, front sway bar, HD rear springs. For me it was fun to drive the heck out of and hang the tail out anytime you felt like it. It needed a bit more front bar to balance out the rear bar to handle well though. For me I preferred it to no rear bar but you had to be aware of what you were doing not to loop it if you weren't paying attention.

[70 Challenger Lover]

Call Firm Feel, I ordered thier 1 1/8" front bar and was going to order a larger rear as well but the guy told me it would handle better with the stock 3/4" one.

That's because Mopars are already over-sprung on the rear with the factory spring set. Going too large on a rear sway bar will make them even more tail happy, unless you also step up the torsion bars a few steps to offset the rear spring rates.

So if I were seeking out a more balanced suspension, what would you recommend? My 318 car has the wimpy 318 springs out back. They function fine but I believe the rate is somewhere around 90. I see Eaton offers a 115 rate which I was planning upgrade to. It's a 340 car now so I'm seeking slightly sportier handling.

The front 318 torsion bars will soon be swapped for 340/383 bars (778-779) and I'll add a small factory front sway.

I guess my question is how to determine when the car's suspension is balanced front to rear.

I assume you have a convertible by your avatar? If so I'd stick close to stock, as the whole car will end up being a torsion bar without the strength of a roof. The chassis will flex lots in stock configuration. If your not to concerned about keeping it original , first thing I would do would be adding subframe connectors and torque boxes.Last part I would add would be the rear sway bar for handling improvements.  But being a convertible I assume you want to leave it as stock as possible.
I'd suggest good shocks first, double adjustable if money permits. I have the QA1 shocks on mine for over 10 years and am happy with them. 

I assume a genuine 340 Cuda would come with the 340/383 torsion bars plus front and rear sway bars. That was pretty much what I had in mind for now. Someday, I want to add gills and go full Cuda. That means a complete repaint. When that day comes, I'll strip it to a shell and add the nice looking sub frame connectors then.

I do plan to save up for a great set of shocks.

[Mr Cuda]

/quote]

You have to drive it with no or disconnected sway bars. If the front feels soft or pushes,  raise the front  to see if it gets better when firmer. Then you will know if you need bigger torsion bars.
 A stock barracuda with no sway bars is neutral on a wet corner. But boy does it lean. Convertible will handle better,  but I've never driven mine with no bars. I gave you my combo.

[70 Challenger Lover]

/quote]

You have to drive it with no or disconnected sway bars. If the front feels soft or pushes,  raise the front  to see if it gets better when firmer. Then you will know if you need bigger torsion bars.
A stock barracuda with no sway bars is neutral on a wet corner. But boy does it lean. Convertible will handle better,  but I've never driven mine with no bars. I gave you my combo.

I drove the car for four years in stock 318 form with good original suspension. It was soft and comfortable but it really rolled over during even gentle cornering. I had the exact same setup on a hardtop 318 Barracuda so when I freshened up the front suspension, I added a factory front sway bar and noticed a nice improvement in the corners.

My convertible has good suspension all around but it's basic 318 stuff. I have swapped to a 340 four speed and in keeping with the Cuda upgrades, that's the real reason I wanted to redo the front and rear suspension. It's not that I'm unhappy with how it drives now. I could add a factory front sway bar to it like I did the hardtop (just to firm up cornering) and it would probably be great.

It almost sounds like I shouldn't upgrade torsion bars, leaf springs or add a rear sway bar. It's just a back highways cruiser. Not carving corners. I just figured a proper factory Cuda conversion meant stiffer suspension and a rear bar.

[70 Challenger Lover]

Add an edit.
Depending on ride height,  the. 890 bars could be too soft.
 Torsion bar spring rate is calculated with the  lower arm and travel.  Rate builds progressively.  No travel,  no rate.
 I put 318 .860 bars in a 440 car and had to crank the adjuster all the way to get ride height.
The problem with this is when the car leans,  the inner bar is trying to unload its massive tension, and adds to the lean.  For a drag race launch, it helps lift.
This was for a highway flier, so to control lean, I have 2 front sway bars.

When I redid the suspension in my '69 Coronet, I discovered the guy who tossed it together added a 440 but kept its original 318 bars. It too was adjusted to maximize and had nothing left to give. Putting in the correct bars for that motor, I noticed a huge improvement.

I often see guys post how our cars were under sprung and how they benefit from the fattest bar that will fit but this never seemed believable to me unless the chassis was reinforced and the car used in road racing.