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Author
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Topic: twisting on launch
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-28-2004 11:51 PM
  
I took my car to test and tune tonight for the first time with my new 408C. 60 foot times were 1.48 and ets were 10.80@122mph in a strong head wind and a soft tune up. I launched with the 2-step at 2800 and it picked up the drivers side front tire 10" and carried it 30 feet. The passenger side barely left the ground. It's a Fairmont/fox chassis and has frame conectors, 10 point roll cage, Strange coil overs in rear. I'm using adjustable rear control arms with solid bushings. The front is mostly stock with 90/10 struts.
I tried stagering the coil over settings, but never could get any of the twisting out of it. What should I try for settings? Is it time for an anti roll bar? ------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 351C 4V
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steve'66
Gearhead Posts: 9104
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 04-29-2004 12:20 AM
quote:
Originally posted by clevelandstyle:
Is it time for an anti roll bar?
NO, not yet.  SteveW
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-29-2004 12:27 AM
Okay. Give me a hint on what settings to try.  ------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V
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Tbird
Gearhead Posts: 298
From: USA
Registered: May 2003
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posted 04-29-2004 06:16 AM
Is the car really twisting or is it the appearance of twisting?On launch, the passenger rear tire is drawn into the fenderwell while the driver rear tire is forced out of the fenderwell. This gives the appearance of body twist in lots of cases when it lifts the driver front tire. I would look into maybe preloading the passenger rear spring and adjusting that shock tighter on the compression adjustment. The driver rear shock i would tighten it on the setting to prevent extension. The driver front shock could be set tighter for extension also. These adjustments are made easier if you have double adjustable shocks.
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-29-2004 08:08 AM
It appears to be the suspension. I only have single adjustable shocks in the rear. The fronts are fixed 90/10. I can preload the spring and stiffen the shock on the right rear easy enough. It just looks like there is going to be a gross stagger between the right and left shock. Is that normal?------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V
IP: Logged |
Tbird
Gearhead Posts: 298
From: USA
Registered: May 2003
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posted 04-29-2004 09:06 AM
It is not uncommon to have what you call, a gross stagger between the two rear shocks. It is not uncommon to have the passenger shock 4-6 clicks stiffer than the driver side rear shock.
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steve'66
Gearhead Posts: 9104
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 04-29-2004 10:50 AM
Ben,Raising the front left on launch does load the right rear (which is a good thing to a point). It can be controlled by stiffening the right rear shock. Read this article, http://racingarticles.com/article_racing-50.html SteveW
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Capri
Gearhead Posts: 1484
From: Lyons, ILL, USA
Registered: May 99
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posted 04-29-2004 11:06 AM
I am thinking you might have to preload the passenger side more to raise the body and stop it from squatting. Last year we put adjustable control arms on my Capri. My car was leaving similar and it was close to digging the body into the right rear tire. We saw it in a picture. We changed the setting on the right side upper bar, and raised the body by adding the preload to get the car to leave square. Having a video of what the car is doing from directly behind the car and a touch to the passenger side will help show you what the car is actually doing. When you get it to leave square, it will 60ft faster!  Also look at the car when its sitting level. Does it appear as if the passenger side ride height is lower than the drivers side? If so, you will have to add more preload for sure.Now just to add something else into the mix, what did you have your shocks set at? Normally an a very good working car, 1-2 clicks stagger is all you would need. If its a coil over car, alot of guys run 2 different spring rates and set the shocks equal. I hope I didnt confuse anyone! Tony
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-29-2004 01:12 PM
Tony, you are talking about preloading the right upper control arm, right? Does that mean preloading it forward or backward? Did I confuse you? 
I started with 3 clicks on the left spring and 4 clicks on the right. I ended up with 2 more clicks on the right but it didn't help much. I think some extra spring load on the right may be in order. The car sets about level at rest. I can raise it to see if it helps. They are 150lb springs now. ------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V
IP: Logged |
jim1320
Gearhead Posts: 198
From: white plains, maryland, usa
Registered: Apr 2003
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posted 04-29-2004 03:59 PM
Sound Great !!! tell me more about your motor carb. intake heads good luck jim1320------------------
1970 Mach 1 393 stroker cleveland best 10.88 @123.50 3550 lb car with exhaust have fun!!!
http://www.hardcore50.com/race_coverage/MIR-FordFeverClassic/2003/PICT0034.jpg
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-29-2004 07:46 PM
Jim,
It's a Scat 4" stroke 4.03 bore. Ross reverse domes. Heads are 4Vs with a garage port job. Holley Strip Dominator intake and Holley 850dp for now. Nothing real special. It feels like it has a lot of torque. It's a hand full through first and second gear. I think when the chassis is lined out and I put a better tune up on it, it will be solidly in the mid 10s(or better). ------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V
IP: Logged |
70coupe
Gearhead Posts: 471
From: Toronto,Ontario,Canada
Registered: Aug 2000
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posted 04-29-2004 08:00 PM
What cam are you running in this motor and what do you have your total timing set at?
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-29-2004 09:09 PM
Cam is a roller 258/[email protected]" .630/.658Timing is at 34* right now until I get the chassis dialed in. Then I will bump it up a bit. I'm running pump gas at this time. I will also try some racing gas later. ------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V
IP: Logged |
70coupe
Gearhead Posts: 471
From: Toronto,Ontario,Canada
Registered: Aug 2000
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posted 04-29-2004 09:43 PM
Just curious, what LC on the cam?
Thanks
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clevelandstyle
Gearhead Posts: 1098
From: Connersville, IN
Registered: Jul 2001
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posted 04-29-2004 10:42 PM
108 lca------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V
IP: Logged |
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