torsion bar handling

i figure this is the place to go for this, as the mopar boards arent really getting me anywhere.

also, the musclecar boards arent really up to speed on the old mopars, either.

what im working with is a 1970 plymouth duster. 360, 4 speed. aluminum heads, sluminum intake, aluminum water pump, fiberglass hood, aluminum radiator. battery in the trunk over the rear axle.

ive done my best to jockey the weight where i can to make it better balanced.

i plan to start autocrossing this car in spring, as ive already proven you can autocross a truck. now im goingto prove you can autocross a duster,

the suspension is fresh. adjustable strut rods, poly UCA bushings, subframe connectors, 340rear leavs, big bloc torsion bars, KYB shocks, poly rear spring bushings, 1 1/8 front sway bar, 3/4 rear. fast ratio steering box, big brakes. 17X8 whels, 255/40/17 front, 255/50/17 rear.

car has been lowered all teh way around to where it looks right. t-bar cranked down in the front, 1 inch block in the rear.

my first couple of pieces to change are to go to 3/8 taller spindles for better negaive camber gain, and offset UCA bushings for better alignmnet specs. im thinking of going with -1.0 camber, +5 caster, 0 toe.

what else should i be looking at here? im wondering if the LCA should be parallel with the ground to make the most of the negatove camber gain like i would with a coil spring car?

any other ideas to help make this thing stick?

ill even add the link to the build thread, just to give you a better idea of what im working with.

http://www.forabodiesonly.com/mopar/showthread.php?t=111545

so let me know what you think. and remember, this has to stay in somewhat of a budget.

michael

Welcome Michael. There are a couple of us around here playing with torsion bar Mopars. The '68 Barracuda in my avatar is mine. It's currently undergoing a 5-speed conversion.

What size front torsion bars are you running now? Are they the .890" 383 A-body bars? How much clearance is left for the lower control arm bump stop at the height you have now?

I used to run the the MP '151 bars (.920") and last year went up to the 1" bars. The big block bars are still a little on the soft side but a good starting point. Several guys are running the 1.06" bars available from Firm Feel in theirs.

I had the KYBs and they rode stiff and didn't really seem to control the springs while autocrossing. I'm running some SPAX adjustables now. They were designed for an Australian Valiant, but they fit great in a US spec A-body. Not easy to come by in the states. Some newer options are GM spec QA1's for adjustables. Bilstein non-adjustables are available for A-bodies now too.

The A's can be a bit tail happy stock. The rear bar is probably too much. I don't run one. You might want to try it both with and without it connected and see how the car feels.

Hey Duster,

looks like you have a good start on a setup.

My comments: 1. Try to keep the LCA parallel to the pavement assuming that it doesn't lower the car too much and screwup your ground clearance. 2. I would start with 2 degrees of negative on the front.

Keep us updated!

Rog

Duster, are you on Mopax?

Try and find out all the info you can abut the Green Brick Valiant. Mopar Action's road race A body from about ten years ago.

http://www.moparaction.com/Article/Brick/GreenBrick.html

http://www.moparaction.com/Tech/archive/one-lap-pix.html

MoParts had a nice discussion with a few links: http://www.moparts.org/Tech/Archive/susp/17.html

Lou Madsen over at Slantsix.org has a 64 Dart road racer that might give you some autocrosser ideas.

One thing I've heard but haven't tried is using Edelbrock IAS shocks. I have KYB's in my Valiant with "340" bars (0.870") - IAS's are on the Want List.

Do you have any numbers, driving impressions, or particular problems?

umm... what is mopax?

right now, there is no hard numbers. just a lot of understeer, no initial turn in, and doesnt feel very planted. im hoping that the tall spindles and alignmnt will take care of a lot of that, but im not holding my breath.

what im starting to so is to do my research. goals for over the winter are to install my parts and fine tune what ive got already. get it out to an autocross or two in the spring, and evaluate from there.

also hoping to do some sessions on track down at CMP thsi spring as well. the truck has ben fun, but now i want to do it in my duster.

michael

My 71 Challenger Conv has produced 1G with mostly stock components.

Heim joint the end links on the front swaybar to reduce bind (This is probably why the car is under-steering so much...it is binding up and the suspension will not move properly & freely). A quick experiment would be to loosen the stacked type end links to the point where they rattle and then drive the same course. Also make sure that the poly strut rod bushings are not binding and keeping the suspension from moving freely.

Lay the caster fully to the rear and live with what ever camber you get out of this. These cars love caster to lean the wheel over in tight turns.

If you are still running rear steel leaf springs, make sure that the leaves are not binding. Add white grease between the leaves and be sure that the plastic slipper plates are on the end of each leaf. Upgrading to fiberglass leafs is the best choice. I took 318 leafs and added a 1/2 leaf to the front of each, worked great. Poly bushing on the leafs resist body roll much like a swaybar...

The KYB's are way too soft in front compression and rebound and too stiff in compression in the rear. There is a Koni fitment for these cars if you call them up and ask...Well worth it!

Add a HEAVY Class III trailer hitch to the rear. If your car is traction limited under power this will help not hurt...plus it is a hoot to tow your friend to the track and then beat him with the Tow car!

Mopax Yahoo Group

Mopax is a mailing list turned Yahoo Group.

From the home page :

"mopax · Mopar autocrossers and road racers

Temporary home for Mopax, a mailing list for Mopar not-necessarily-straight-line performance, including autocross, roadrace, and circle track."

Which "fast ratio" steering box do you have? I'm looking at a 20:1 worm gearset to put in my spare manual stock box. Flaming River advertises one at 16:1, but I think that might be a bit much for a daily driver. I do have to parallel park now and then ...

slantvaliant wrote: Mopax Yahoo Group Mopax is a mailing list turned Yahoo Group. From the home page : "mopax · Mopar autocrossers and road racers Temporary home for Mopax, a mailing list for Mopar not-necessarily-straight-line performance, including autocross, roadrace, and circle track."

It's like Fight Club for us old-school Mopar guys.

Rob_Mopar wrote:

slantvaliant wrote: Mopax Yahoo Group Mopax is a mailing list turned Yahoo Group. From the home page : "mopax · Mopar autocrossers and road racers Temporary home for Mopax, a mailing list for Mopar not-necessarily-straight-line performance, including autocross, roadrace, and circle track."

It's like Fight Club for us old-school Mopar guys.

Then stop talking about it!

*nothing to add to the convo except rampant love for Fight Club and all things Palahniuk

Lots of great handling intel on the Mopax list. There's even a road course event once a year at Willow Springs (or Buttonwillow). Several active Mopar racers, Autocrossers and even some lunatic who raced his '71 'Cuda up Pikes Peak a few times

That guy should have his car taken away from him, have his finger nail and toe nails removed one at a time and the raw flesh soaked in alcohol, then forced to clean toilets till he dies of an infection!

Dusterbd13 wrote: umm... what is mopax? right now, there is no hard numbers. just a lot of understeer, no initial turn in, and doesnt feel very planted. im hoping that the tall spindles and alignmnt will take care of a lot of that, but im not holding my breath. what im starting to so is to do my research. goals for over the winter are to install my parts and fine tune what ive got already. get it out to an autocross or two in the spring, and evaluate from there. also hoping to do some sessions on track down at CMP thsi spring as well. the truck has ben fun, but now i want to do it in my duster. michael

Try running a taller ride height in the front. If I remember correctly, and assuming the T-bar suspension is similar to the 80 Dodge luxo barge stuff I played around with, the Dodges really drop the roll center when you lower them. This, combined with a fixed roll center in the back, will do funky things to your handling.

If that works and you can't stand the looks, try relocating the suspension mounts and/or using a different spindle. The spindle is obviously the easier path.

There's a guy on the Mopax list (former Mazda IMSA driver) who at one time built custom drop spindles for A-Body's. They had the proper geometry. He also had adjustable rear leaf hangers.

I didn't read any of the above.

That said, there is nothing inherent in a torsion bar that would make for a bad handler. It's just a spring. It has some packaging challenges, but it does away with some other ones.

DILYSI Dave wrote: I didn't read any of the above. That said, there is nothing inherent in a torsion bar that would make for a bad handler. It's just a spring. It has some packaging challenges, but it does away with some other ones.

How do I convert the front of my 1st gen. CRX to a Macstrut!?!?

Drop spindles, adjustable spring hangers, monoleaf rear springs, HD torsion bars, adjustable strut rods, Viper caliper adapters ... lots of stuff is available new for A-body Mopars. It just takes money ... or ingenuity.

This guy deserves a special award: Cuda on Pike's Peak

Dusterbd13 wrote: right now, there is no hard numbers. just a lot of understeer, no initial turn in, and doesnt feel very planted.

In Carroll Smith's Tune to Win, he list causes and effects. Does this match what your car does? Corner entry understeer-won't point in and gets progressively worse. If it is he says it can be caused by these things; insufficient front track width, front roll stiffness to high, front roll center too low, insufficient front shock absorber bump resistance, excessive dynamic positive camber on the outside. And from what I am seeing about the KYBs I would guess that might well be your problem.

If it doesn't turn in, and has no toe, why not set the toe out like 1/8th. RWD is usually toe-in, but if it handles that badly, toe-out may help.

Steven

An award? How about a peanut butter and jelly sammich?

Cudaracer 42 wrote: An award? How about a peanut butter and jelly sammich?

I'll bring ya one if you come to the next Spring Fling Speed Festival ....WITH the 'cuda!