70 Challenger & Autocross: Suspension Dilemna

[70challenger23]

Hi all, I picked up a 70 challenger about a year ago and am in the works of getting some motor work done in dallas. While the car is done I will be going through the car to freshen things up a bit and suspension is on my list. The motor will be putting out around 500-550 by the time all is said and done. Its primary use will be mainly for some weekend hotrodding and the occasional dragstrip visit to terrorize my dads 69 chevelle. With that being said I really want the car handle really well as opposed to being fast in a straight line and possibly sit a little lower while I'm at it. I am certain there are some AutoX gents on here that can shed some light into what their setups may look like. I know hotchkis makes a great setup but after this motor expense, I'm not looking to spend an outright 3,500 anytime soon. I was raised by my chevy father so my mopar knowledge base is bleak. Always loved them since I was a kid so I had to betray him....now he is just focused on beating me in everything I appreciate the knowledge in advance. 

[brads70]

Welcome!  I would start with torsion bars, sway bars and shocks. Tires are very important also. You will find  you will need to go to 17" and better yet 18" to get sizes for performance rubber. For torsion bars I would suggest 1.120" or bigger. Mopars are horribly undersprung from the factory. For sway bars Hotchkis, PST, Hellwig , Firm Feel , all make tubular sway bars ( lighter is better) Shocks , Bilsteins, QA1, Hotchkis all have offerings.
In my signature there is a link to what I have done with my car. I'm sure I have the $3500 or more spent you mentioned but I didn't do it all at once either.

[dfrazz]

This is by far the best site for e-bodies, all good guys with an incredible amount of knowledge.  I just spent the past winter putting on a completely new bottom end of my Challenger, including motor, disc brakes and suspension. Brad nailed it with everything to consider.  The torsion bars will adjust your ride height. There is a 3/4" bolt that is sticking out the bottom of the A arms. Turn it clockwise to raise the car, counter-clockwise and it will lower the car. You will need to measure, make adjustments, then bounce your car on both sides and front, then re-measure.  When you are close to the height you want, take it for a spin then come back and re-measure.  When selecting new wheels/tires, obviously watch for tire clearance on the fender and turn radius.  There is a sticky thread on here dedicated to tire size combos. You will want to get an alignment after you get the wheels/tires and torsion bar height set. 
For shocks, I went with Bilstein shocks and am very happy. You may want to consider adjustable (single or dual) and QA1 makes a good set but they are more expensive that straight Bilsteins. 
Your rear springs are going to be critical both for height and ride.  A good source is ESOP (http://www.springsnthings.com/) as they are made in the USA and will send you an exact set up, or you can always go to a local spring shop and save on shipping which is what I ended up doing.  For $3500, you will not be able to afford a Hotchkiss or QA1 K member, tubular arm set up but if you are just messing around on the streets you will not need that to still have a good performing car.     
If the suspension is fairly old, you will want to change out all the bushings too.  Moog is what I went with as they are made in the USA and great quality.  There are many China made products here, and PST sells them without telling you so be careful.
Other good sources to buy from: Rosevillemoparts.com (ask for Dave, he is a member here and will give you a discount), and Manciniracing.com (all mopar, sell Moog bushing sets, Bilstein shocks, etc).
This is just my    and I'm sure others will chime in.

[Mopar Mitch]

You've stated 500-550 HP... is that with a BB or SB engine?   One of the easiest things you'll want to do is reduce weight everywhere possible.  Consider:  T/A fiberglass hood, aluminum master brake cylinder, light weight driver and passenger seats (plus they'll support you much better in the corners), light weight rims (8" minimum width), 200 tread wear tires front and rear, light weight Denso alternator, no stereo or speakers, no air conditioning.   These items alone will knock off about 150 pounds.

[jordan]

I think you are walking on a slippery slope.  Its going to be tuff to get all motor and then hold back on the suspension.  You can piece the suspension together as you go along, but it may be beneficial to hold out, and save you money, and buy a system that is made to work together.  Matched springs and shocks go a long way to creating a balanced car.  Im not saying you can't piece together a good handling car, but a known product is better than piece meal products and hope it works.  Once you get your suspension done, then you will want to upgrade the brakes.  And then the seats to handle the cornering.  It just keeps going and going.  $3500 will get you started with wheels, bushings, and the highest quality shocks you can afford, but you will still need front and rear springs, and sway bars, and eventually upper control arms, and end links, and  steering box, and a brake upgrade.  None if it works great until you brace the chassis. 

     My opinion is to build your car, drive it until you save for the next step.  Or wait and make a big project out of it!!   

[Bullitt-]

Think I'd start with a chassis stiffening kit.... http://store.uscartool.com/mopar-parts.html

[70challenger23]

I appreciate all the replies everyone. Not sure if this forum notifies all in the thread of the reply but hopefully you guys see it. I guess I should give some more information...

The motor is a 383 being built by Long Racing Engines in Texas. Going to be hot tanked, blueprinted, stroked...whole nine yards. Starting there out of necessity as it is in rough shape motor wise. Has a r/t hood, factory 4 speed, bucket seats (will need better), 17 inch AR rims and M/T street tires. No radio, speakers or A/C. I am inclined to pay up front for quality parts to save in the long run so thank you for the good ol' USA suggestions!

Plans are to put QA1 shocks and replace bushings  to start. Who would you suggest for springs and torsion bar? Ill work on brakes, control arms, sway bars after the old stuff is out.

[brads70]

http://www.firmfeel.com/   This place is the original go to place for Mopars that handle!

[crash340]

 :thumbsup:for FirmFeel, they are a good bunch of guys

[Chryco Psycho]

There are lots of companies selling suspension upgrades converting to full coil over or air ride etc , but the reality is Mopar had one of the best suspension systems for the day & you can make a lot of improvement using stock  upgraded suspension

[Mopar Mitch]

Firm Feel will work with you the best to setup or custom-make products needed.  As for shocks, consider this one of your most imprtant decisions... double adjustables (example QA1, and some others) will offer you the multitude of fine-tuning the ride pending your place of competition, etc.  Remember, too, that any comprimises in your setup will cost you "time" (fractions of seconds that add up) in an autocross.  In other words, go all-out no les than the best class competitor, or else your sacrificing valuable time.   Read the club's rule book and build your car according to the class you want to compete in... and maximize the allowable modifications.... its just time and $$$ at your discretion.

[70challenger23]

Great, thanks for the site. Will check it out. What is the biggest wheel size (width) you can fit in the back?

[Chryco Psycho]

depends on the diameter of the wheel , 18" you could get 10" wide , 15" more like 8.5" , but you can use offset hangers for the leafs & get a couple more inches easy .

[brads70]

I have 18X11" rims with  295/40/18 tires out back with the b-body width rear end and offset shackle/hangers.

[Mopar Mitch]

The size of the tires depends on the backspacing of the rim:

7" width needs 4" bs (that is factory stock for proper centering)
8" needs 4.5"
9" needs 5"
10" needs 5.5"

These backspacings will keep your tire "factory centered" as the factory rims would do. 

However, the tire's diameter is also a factor in relation to the height and fender clearance.  As a safety factor, plan on, at least, rolling the lips flush.

On my Challenger, with my "race" designated autocross rims of 16x10, and having a 5" backspacing (actually pushing the rim out towards the fenders by 1/2"), and with my past BFG Comp T/A "R" series 255-50-16, then later 275-45-16 Hoosier A6 race DOT autocross radials, I've modified the fender lips as needed by flushing them and slightly pulling them outwards... the fronts were easy (1-night for both); the rears had their lips cut, flushed/rolled, pulled outwards as needed, then re-welded at the cuts and epoxied over inside... spent 1-night each per rear fender... result is the lips (front and rear) still "appear stock", can even still accept the factory chrome edging.  The suspension is stiff for extreme competition autocrossing, the body barely leans in the corners; you can barely fit your little pinky fingers between the tires and the fender lips... no touching at alll even under extreme cornering!  NOTE:  IF I wanted to, according to the SCCA "E/Street Prepared" class rules, I could've had full fender flares, etc, but... my body shop guy made them appear stock... very nicely done!

I also have another set of rims, 16x8 vintage "minilites", havin a 4-3/8" backspacing, and I run BFG Comp 255-50-16 fronts and rear... no problems, plenty of clearance (I use these rims/tires for hi-speed road course events).  Then, for the "street/hwy" cruising, I have anaother set of vintage minilite 15x8 rims (4-3/8" backspacing) with BFG T/A 255-60-15 front, 275-60-15 rears... no problems, plenty of clearance, good "cruising" tires!

Also, my leafs are kept at the factory locations (not moved inboard... not legal in my class for racing).

Hope this helps.