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launching problem

2K views 13 replies 11 participants last post by  4thHorseman 
#1 · (Edited)
I've been working with my suspension and have a problem I'm trying to sort out. Any pointers sure would be appreciated. The car is a '69 Mach 1. Front suspension is moroso drag springs, 90/10's w/ 5" suspension travel. Rear is heavy duty factory leaf springs, Cal tracs and 70/30's. Car weighs is at 3300, 545ci w/ 4000 converter and a C6, 3.89's on a spool, 28x13.50 ET Streets. neg 4 degrees pinion angle at rest.

On launch off of foot brake @ 3000rpms, the car hooks and tosses the fronts up about 8". The rear of the car lifts slightly per anti squat. The front tires immediately come back down but the front suspension remains fully extended with the hood way up. The car seems to bounce, like gasser style, for a few lengths as it is propelling forward.

The car reacts the exact same way cruising at 65mph on the highway. I remained in 3rd gear, 3000rpm, and matted the throttle with the 175hp nos hit armed. Hood came way up, car got all out of shape and the rear suspension seemed to bounce a few times as the tires attempted to dig in and stay planted. Between the car getting squirrely and the jouncing its a little too sphincter tightening trying to keep it straight. I'm looking to make the bounce go away and smooth it all out.

Any clues as to what I have setup wrong???
 
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#2 ·
a 90/10 is good to get the front end up initially. but will be slow to let it down. I had better luck on my stock front suspension with the Koni shocks, i think even afco now makes some stuff for them.

Cant help on the rear, not too familiar with the Cal Tracks. A good set of double adjustables will go a long way on the rear as well.
 
#3 ·
Here is some good info on basic set-ups...It is a very fine line between having a car that works well on the track and still has good street manners...tough to get both without having some adjustability. Dilligas seems to have a wealth of knowledge about set-ups and I'm sure he will chime in with good info for ya'...

In the meantime, here is some good reading...
http://www.competitionengineering.com/articles/ArticleMain.asp
 
#4 · (Edited)
if it is bouncing in the front too much you may need a 10 way double adj. shock in the front and possible rears. if you look at my video in the engine build sec. on the 1st page, the 1st pass my car was bouncing real bad in the front, thats why it was drifting left. i had 90/10s now going to adj. struts in the front. you can control up and down travel of the strut. i have been told that the lakewwod 90/10s are set up for small blocks and not big blocks. how true i dont know but my car bounces to much when it comes down. some video will help.
 
#5 · (Edited)
Rancho makes some double adj that will fit the rear, Cal Tac's are good with good springs I broke the springs on mine, need adj shocks on front loose ext. slow down compression, I had some special rear springs built with a extra half leaf forward the rear end and clamped the front of the springs together. I currently have opentracker (highly reccommend them) roller bearing set up on the upper and lower control arms and designed my own double adj. strange coil over set up for the front, I really got serious and just four linked it with big ole tires
 
#6 ·
As I have said before I reeeeally hate the Caltrac stuff in combos that have engines with decent torque numbers. But as these guys have said good externally adjustable drag shocks front & rear go a long way toward helping you managing the violent nature of the Caltracs & help make ironing out the car a little easier.........more adjustability is "more gooder".

You might put "Caltrac" (or Cal Trac, or Caltrack) in the search function because there has been a lot posted about them. Greg & a number of other guys here have been spending a lot of time working on them, and have posted a lot of good track testing results (& video).

Good luck.
 
#7 ·
Dave,

I have been struggling with the damn cal-trac setup for a year now. All I know is my car isn't any faster, and I'm very very frustrated.

Maybe a damn near 4200 lbs car with a 120" wheelbase is outside the parameters for success with the calvert stuff.

They have been working with me, though, so their support is a plus.

But when I get the feeling that I need 300 lbs of weight in the trunk to make 1200 bucks worth of suspension crap work I get sour.

Greg
 
#8 ·
Maybe a damn near 4200 lbs car with a 120" wheelbase is outside the parameters for success with the calvert stuff.
Greg, that is a very good point & very possible. And the torque numbers a 460 is capable of could be aggrivating the situation. But you have to admit that your testing has shown success in that you have been able to make the setup more managable and not as crazy-violent....that shows progress in my opinion.

Like or hate their design, the fact that they are willing to work with you & not ignore you after getting paid says a lot about their customer service.
 
#9 ·
I'm definately taking the fully adjustable shock advice. The el cheapo boingers I have now, well, ya get what ya pay for right? I'm thinking I want to get the nose to settle down faster and try a stiffer rear setup.

The 90/10's do toss the front up quick, but the problem I see with mine is it stays up. Would be better if they settled down way more, even slowly, so the car was back at its normal stance for the top end charge. 3rd gear with the front suspension all extended on the inner tread of the pizza cutters is spooky.
 
#10 · (Edited)
I haven't purchased them yet but Calvert makes a 90/10 shock with dual valving that are supposed to settle the front end down. My truck does the same thing but with the drag radials it doesn't skate around like it does on a bias ply slick or et street. It should bring the mph up too because of better aerodynamics. I have the Rancho 9 way adjustables in the rear but with a slapper bar and it has helped alot. I just have the cheap Summit 90/10s as of right now.

http://calvertracing.com/frontshocks.php
 
#11 ·
I use the caltracs on my 514 mach 1 3400 lbs. with me in it.I had the same problem with the rear bouncing they said I needed stiffer rear shocks and recommended adjustable rancho truck shocks they sell them modified to fit.They also recommended there split leaf mono springs.I put on the shocks and had to play with the adjustments to tune it but it did help get rid of the bouncing off the line and handle alot better.I used stock small block front springs and comp eng. adjustable shocks set at 90/10.
 
#12 ·
Think you are on the track with adjustables - the 70/30s in the back you list I would not expect to work well with the cals. You need at least the Ranchos in the back - tighten those up to 7 or 8 and then see where your are. I used to use 50/50 CEs in the back, the Cals ate two sets at my low power level so at your level a cheap 50/50 or 70/30 would be almost like no shock at all.
 
#13 ·
Are your shocks in the back long enough? We have a pretty quick leafsprung street car (11.0s-high 10.90s pump gas no traction bars or cal-tracs just a snubber) and we had stock shocks on it and they were too short and it would act like you described in your first post when you'd hit it launching or when cruising and standing on it.
Good luck,
Jr.
 
#14 ·
That's a good question. I was told 5" front suspension travel is good. I don't know what is required out back and I've never measured it. I was just told it had to be pretty stiff. I have a stock type, cheap drag shock on the rear currently. I guess I should measure and maybe try extensions and see if it helps cure the bouncing.
 
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