Interesting torsion bar discovery...

While preparing for a "driveway alignment" recently so I can drive it to the shop with a rack, I made an interesting discovery. My '72 Dart, which I had purchased as a rolling shell, has the proper .92 torsion bars for the big-block... but they’re both for the same side of the car! No wonder one height adjustment screw was set so far different from the other.

Can I run it like that, or do I need to get the complementary (892/893) bars? The car does sit level.

They should be the same spring rate, I don't see any other side effects other than the adjustment itself may be limited on the range. Curious what others thing as well.

I just found this 2002 article by Andy F. and it says not to
http://arengineering.com/tech/torsion-bar-tango/

Big block bars are .890". Are you sure you don't have a part number that ends in 892? If so, those are 340 bars (small block handling package).

The A body .920" bars are MP bars, not OE. I don't have mine in front of me, but I don't believe they are side-> side offset. If they are the .920 bars they work nice on the street. It's not hard to install them incorrectly-DAMHIK, I'd personally get it right.

Thanks Jim, you are right. They are both 892, and they are definitely offset differently.

It's not hard to correct, just expensive (as usual with our Mopars!) Just want to know if I can run it that way until the budget allows for a new pair.

Edited to add: I mean the 892's have an offset, obviously they're not different from each other

I know that some advise against it but I have used torsion bars in both directions and have not had a single problem. I suspect that the larger the bar, the lesser the chance that anything could hurt it.

You should be fine until you can change them.

You are twisting one bar against the preset and the other with the preset. It might not matter on a thicker bar but you could snap a thinner bar by installing it on the wrong side.

i always thought that after a certain size, both bars were the same part number ? i don't know ?

That is true but it happens at a bigger size than 0.920 which is what the OP has.

OP has .870" bars.

Not likely to snap one unless it's damaged already.

Ah I see. He said he had 0.920 bars but he was incorrect. He just has OEM bars which should be offset half a flat opposite of the twist direction. He might not break a 0.87 bar but he isn't doing it any favors.

Thanks for the update, everyone.
If I do buy a new pair, what would you recommend? .92 or even larger? I know 1.03 are available but those seem awfully stiff

Mostly street, occasional strip. Forget the 90/10 shocks, I think those would be really weird to drive on the street.

I'm not planning to go autocrossing, and soon will be installing homemade (2x3 box tubing) welded frame connectors. The big-block A-body is already nose heavy and I eliminated the back seat which probably makes the weight distribution slightly worse.

People that are concerned that a 1 inch torsion bar will be too stiff have never driven or been in a car that had them.
My 70 Charger has 1.15 bars and rides about as firm as our 2015 Challenger R/T. The torsion bars and leaf springs need to be complimented by the right shocks though. For many years, I had 1 inch T bars and KYB shocks. Now, The car actually rides better and has more control now with bigger T bars and Bilstein shocks.
A 383 or 440 A-body needs more spring rate than a 318-340 car. Mopar had soft spring rates back then. Bigger torsion bars are just a part of bringing the ride and handling quality up to modern standards.

Thanks
Firm Feel makes a 1 inch bar... PST has 1.03" for an attractive price, but it is not clocked (front and rear hex are not offset) and many people have said their A-body's ride height is too low even with the adjusters all the way in

The B-body has a longer bar than an A-body, so I'm not sure exactly what a 1.15" bar would translate to for my car.

As with everything else street/strip, it'll be a compromise. I was thinking about .92 bars because I do want some weight transfer on launch. I wonder how much a 1.00 bar would hurt 60' times?

My son's '67 Barracuda has 1.14" bars and had KYBs with 235-60-15 tires all around. It also had a iron headed 383 with a four speed. I don't think the ride was as hard as my 2004 BMW 330Ci convertible with sport suspension and low profile 18's. I don't find either ride unacceptable...

Well, the B body LCA is actually about 1/2" shorter than the A-body cars so the leverage is slightly less.
An A-body with a 37" bar at 1.0" may not be much different than a B-body with the 41" bar.

The B body bar will have about 10% more twist in the torsion bar for the same diameter, material property, and torque.

phi = 32*L*T/(G*pi*D^4)

phi: angle of twist
L: Length of bar
T: Applied Torque
pi: 3.14...
G: Shear Modulus of Rigidity
D: Diameter of Bar

https://www.engineeringtoolbox.com/torsion-shafts-d_947.html

My 2 cents. Stiffer bars are the way to go, you have to make sure you have a good quality shock that go with them. My '68 Dart is 3500 lbs w/o me and with a full tank of gas. I have 1.18" T-bars and Fox Adjustable shocks. It drives like a modern car. I want a 1.24" bar.

As for left bars or right bars... idk anything about that...

10% more twist?
Do you mean that it is less effective because it twists MORE or more effective because it resists twist 10% more ?

Because the B-body T-bar is longer, it is less effective because it twists more.

A 1" B body bar is 175# wheel rate. A 1" A body bar is 195# wheel rate. Wheel rates are the springs applied force at the center of the tire's contact patch. This is how you can compare different spring rates and suspension designs to come to an apples to apples comparison of rates.

In my experience, a larger bar gives up an amount of 60' time, however, it will be much more consistent and repeatable than a lighter bar and 90/10 shocks.

My drag car with SS rear, light front end rates, no sway bars, and adjustable drag shocks would run 12.2-12.6 and was variable with track prep and atmospheric conditions. The same driveline in my handling car with heavy t-bars, large front and rear sway bars and much wider tires all around would run 13.2 run after run after run. If you're a bracket racer, you know which one you need to have to win.

Thanks. I am not planning to run limp t-bars and 90/10 shocks on the street, where my car will be 90% of the time.

I did some more reading... turns out PST now makes the 1.03 bar with the proper clocking (too many complaints/returns from people who didn't want the "slammed" look). $239 with free shipping. I also learned that as a FABO member I get 10% off. Down to $216. Not bad for new bars!

I've tried many different sizes of TBs in the Challenger... and some different shocks.. and different leaf springs... for the purpose of competition AX/HSAX... settled with the 1.24 TBs... they are great! Yes stiff, but still drivable on the street and highway... as long as you avoid rough roads (race tracks typically are smooth!). Tire pressures and sidewall aspect ratios matter, as well, so, it becomes a compromise to accept what you've got and learn to drive the car with the setup. A benefit of larger TBs is that they also reduce lift and dive.

The reduction in that lift and dive is where bigger bars give up performance at the drag strip. However, they are much more consistent in the e.t. department and are a significant improvement in street manners. I think Dr Charles will find the 1.03 bars for his dual purpose car will give me a much better mannered street car but will cost him some in the ultimate e.t. at the track. IMO, a fair trade off for something that is 90% street orientated.