advice on rear suspension work

[68firebird]

Hey guys. I read this forum alot but dont ever post anything. Now I need help with some advice setting up my rear suspension. I have a 1968 Firebird. I will give you some info about the car and then hopefully someone can help me out...please. I have a 434 sb chevy motor with a th350 and a converter that stalls to 4700rpm with the transbrake. The car weighs 3260. I made 475hp to the wheels and 615 to the wheels on spray. My issue is traction. I have 90/10 comp. engineering front drag shocks and Moroso trick front springs. 8-point cage. Stock rear leaf springs and comp. engineering rear drag shocks. I have comp. engineering slide-a-links which made a big difference but I have been told that I need to change the rear leafs and to go to a much much more expensive adjustable rear shock. I have 4.10 gears and hoosier quick time pro's, 29x11.5-15. At us41 on Friday night I ran a 10.86 at 125mph with out nos (didnt spray that night, to slippery) My 60ft were averaging aroung 1.65 to 1.69. With my 406 and MT E.T. Street's last year my 60ft were 1.51. I have never went there at night before and someone told me that's when it's the slipperiest. I know it will go much faster if I can get the darn thing to stop spinning. Please any help would be appritiated.

Thanks, Chad

[TuffGuy]

make sure the front shocks are on the lightest setting 90/10, if there is a front sway bar, take it off, if the front end has limiters loosen them up to get as much weight on the rear end as possible. What rear shocks ????? With the slide a link you might be "topping" out the shocks. The least expensive way is to use the $50 CE rear shocks w/ shock extensions.
my .02

[ICON]

whats the pinion angle?
whats the height and spring rate of the front springs?
condition of tires?
how much does the rear of the car squat when you launch?does it pop right back up?
video would help.
track slippery or was your setup not digging into the track?(US 41 HAS TAKEN MORE THAN ITS SHARE OF PARTS)

afco and qa1 do make some quality adjustable strut and shocks you should consider looking into them.
you could also change the front/rear to a coil over setup this would help you fine tune your suspension.

[68firebird]

Thank you for all the advice. The pinion angle is around 3 to 4 deg. neg. I called Calvert Racing thismorning and orders a set of leaf springs for my car. They set them up for your application/ $317.00 shipped to my door. Then I realized I needed shocks so I called them back and orders a set of Rancho9000 truck shocks. It's what they reccomended for race application. Fully adjustable to. I will have it all by Mondey od next week. He also said they your typical $40 90/10 front shock isnt worth a crap. He will have REAL 90/10 front shocks in about 4 weeks for $110.00 for the pair. I also ordered a set of Mickey Thompson ET Drag Radials to replace the Hoosier Quik Time pros.

[Newbomb]

I had CE 3 ways.... 90 / 10 on the front and 50/50 on the back...with slapper bars, 275 55 D 14 hoosier quick time....I dead hooked 1.7's lol not bad ;) yankin the front tire runnin 13.3's!!!

[Draggin My X]

Thank you for all the advice. The pinion angle is around 3 to 4 deg. neg. I called Calvert Racing thismorning and orders a set of leaf springs for my car. They set them up for your application/ $317.00 shipped to my door. Then I realized I needed shocks so I called them back and orders a set of Rancho9000 truck shocks. It's what they reccomended for race application. Fully adjustable to. I will have it all by Mondey od next week. He also said they your typical $40 90/10 front shock isnt worth a crap. He will have REAL 90/10 front shocks in about 4 weeks for $110.00 for the pair. I also ordered a set of Mickey Thompson ET Drag Radials to replace the Hoosier Quik Time pros.
Now that you've put all that money in a good setup, go out and buy you a good set of slicks!!! You can't beat 'em!!!