(VIDEO) Suspension HELP for 70 dart swinger drag racing!

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  1. y26

    y26 Member

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    [YT][/YT]
    Hey guys, looking for some help with the suspension on my 1970 dodge dart swinger. Car has a 340 with around 450-500 hp, powerglide transmission with transbrake (leaving around 4000). In the front I have new qa1 control arms with 90/10 shocks and mopar performance torsion bars, The car has good free travel of 5+ plus in the front. Going to the back I have the subframes connected, calvert mono leaf, caltracs, qa1 single adjustable shocks. The car has also been minitubbed with leafs relocated allowing me to run 28x11.5x15 MT ET Drag slicks. I ran last weekend at a local 8th mile strip, best run was 7.23 at 93.3mph with a 1.58 60', but cant get the car to leave the line without spinning. Tried caltracs in both top and bottom hole, preload and no preload on both, shocks set all the way loose in the back, tried tire pressure from 9.5 all the way to 13.5(ordered tubes to help stiffen sidewall of slicks now). Any suggestions are greatly appreciated! Thanks, Cole.
     
  2. yellow rose

    yellow rose Overnight Sensation

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    You need double adjustable shocks on both ends.

    You are hitting the tire too hard on the initial hit and the tire is bouncing back.
     
    • Agree Agree x 1
    • spl440

      spl440 Everybody's Fool

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      Also looks like rear shocks might not be long enough
       
    • y26

      y26 Member

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      Thanks! Any suggestions which shock to get?
       
    • Cudafever

      Cudafever Well-Known Member

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      Agree!
      The first motion is crush the tire, then the front end lifts. As the tire rebound,(rear tire) then you get a full turn of the tire, suspension(rear of car) come back down and then it re hooks.
      NICE SLOW MO VIDEO !!!

      I wouldn't pass up looking at the length of the rear shock, but double
      adj is were i would spend the money.
       
    • Cudafever

      Cudafever Well-Known Member

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      You went with QA1 control arms.....they make good double adj shock as well.:poke::thumbsup:
       
    • Cudafever

      Cudafever Well-Known Member

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      Before you buy new shocks, try stiffening up the RR Shock a couple clicks. It may not fix you problem, but should help.
       
    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      The rear certainly isn't lifting as high as it should. That indicates it's not planting the tires hard enough. Something in the rear is not right.
       
    • justinp61

      justinp61 Well-Known Member

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      I'm not familiar with QA1 shocks so when you say full loose you mean full loose on the extension? If so IMO you're going the wrong way, you need to tighten it up to slow the lift in the rear. It hits the tires hard, picks the front end up and when it sets the front down unloads the tires.

      I run a 28 10.5 and a 325/50 radial on my Dart with Cal Tracs, monos and Rancho 9 ways. My shocks are usually set in the 6-9 range. My bars are in the bottom hole with very little pre load. It's been 1.37 with this set up and will hopefully go lower than that with the converter adjustment. BTW my car has very little rear rise.
       
    • yellow rose

      yellow rose Overnight Sensation

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      QA1's or Viking but they have to be double adjustable. Pisses me off when I see people spend money on 9 way ranchos that aren't double adjustable.

      You need to be able to adjust your shocks for bump and rebound SEPERATELY. Anything else is a huge compromise.

      Outside of some fixed factors, such as engine placement, and instant center, which you can't move very much with Cal Tracs and leafs, or a ladder bar for that matter, the shock is the MOST important tuning tool you have. Then comes the 2 step, if you have it. I doubt your shocks ar topping out. You are beating the snot out of the tire.

      I see guys use up tires in 30-40 runs. The face is fine, but they beat the sidewalk to death and they are junk. You usually see them for sale for a smoking price. They would be junk none the less.
       
      • Disagree Disagree x 1
      • skrews

        skrews Well-Known Member

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        You need to soften the hit and stiffen the tire. More air pressure, stiff wall slicks, run tubes if you don't already have them. Double adjustable shocks are definitely the way to go. QA1 and Viking are entry level, but IMO better than 9 way Ranchos. If you have the coin look in to Afco or talk to Menscer MotorSports — Custom Race Services
         
      • y26

        y26 Member

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        Thanks for all the help guys! I ordered tubes for the tires and qa1 double adjustables (didn't see the Afco/menscer post till now or I would have checked). Next weekend is next race will get videos with new shocks and tubes. Where should I set the shocks for as a starting point? Both tight or in the middle?
         
      • Vitamin c

        Vitamin c Vitamin c FABO Gold Member

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        now tell us how you made that video! go pro??
         
      • replicaracer43

        replicaracer43 Grumpy Old Man

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        He said in another seperate, but almost identical thread, that he modified the shock mounts in a way that REDUCED the avalible shock travel........bad idea, IMO, and I agree with your shock advise
         
      • y26

        y26 Member

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        iPhone 5!
         
      • y26

        y26 Member

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        Correct I did modify them which was probably the wrong way. They will be put back to factory mounts before the next race also!
         
      • y26

        y26 Member

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        Also I cancelled the qa1s and got Afcos. Read a lot of bad reviews and talked to some other racers with bad things to say about the qa1s!
         
      • Vitamin c

        Vitamin c Vitamin c FABO Gold Member

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        nice! that video solves a lot of unknowns, ill see if I cant figure that out on my iPhone. My buddy has a small block dart and has the same problem. Ive been telling him forever that his shocks are to short.
         
      • y26

        y26 Member

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        Any suggestions where to set the rebound/compression for the first run? Tight, loose, half? For slomo on iPhones go to camera and swipe to left on video while recording!
         
      • y26

        y26 Member

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        Well didn't get shocks in time, but moved mount back up, tubes in tired and tightened the single adj shock. Best 60' was 1.54 today leaving a lot better
         
      • Cudafever

        Cudafever Well-Known Member

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        Looks better! Did you run then at the same psi as you did with out the tubs installed?
         
      • y26

        y26 Member

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        That was at 14 psi, the first video was 9.5
         
      • Buschi340

        Buschi340 Well-Known Member

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        wow. thats a difference. what did you do exactly ( in simple english please ) ? my car launches like a parallelogram means it goes off the supension rear and front same time. i race 4 times a year so i never paid Attention that much but now that i see this comparison I am exited to make some Progress on my 2sec 60 ft time....
         
      • 71gtdart

        71gtdart Well-Known Member

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        Wish I would have seen this earlier. I run a 71 Dart with almost an identical set up. Almost never figured out the set up.

        I have a 408 with a powerglide and 4.86 gears. Leave at 3400 on a trans brake. Also have Cal Tracs with Calvert front and rear shocks.

        You didnt need double adjustable shocks, but they won't hurt for sure.

        My car was doing the same thing. Bouncing the tires back off the track and unloading. Calvert kept saying to loosen up the rear shocks. Made it worse. Finally got video of the car, and figured it out myself.

        What to do:

        Caltracs in the top hole

        Zero pre load on the springs. You need to slide a nickel between the spring and the preload tube, then lock it down. do this on both sides. You have to let the suspension have that little bit of room to work and get body seperation from the rear tire. this pushes the tire into the track. If you have preload on the spring it will not allow the shackles to move forward and lift the body at the hit. It just stays in the neutral position since its not loaded while on the transbrake. On a footbrake car, you can preload the spring, because when you stage, you will have the suspension loaded and the shackle will be forward quite a bit already.

        I moved my Calvert rear shocks to the 7th click out of 12, and it worked best there. The shock just needs to have the extension slowed down, so that it gradually pushes the tires into the track instead of squashing them and bouncing them back up.

        I run a 29.5-9-15 slick and run 17-18 lbs in them.

        My car runs 6.70's and 60ft's 1.44-1.45 on Alcohol.

        Even in the heat, it hooks consistent. I made 13 runs last saturday and the 60ft only varied .003 over those runs.
         
      • y26

        y26 Member

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        main difference between the two videos was tightening the rear shock and moving shock mount (back to stock fixing my mistake)

        What do you have for shocks currently? Caltracs?
         
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