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Question about setting up suspension


gbracing81
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Sorry Dave, I was at work and ran out of time trying to embed the videos. So I have been unable to really get the car to launch to what I feel is it's best potential. The best 60' I've been able to do was a 1.42 and I average (at Trails) about a 1.47-1.52. I would like to see 60's in the mid to high 30's. Here's what I'm working with, the motor is a SBC 409 (.040 over 400), Dart IEP 215 ported with 2.10/1.60 flowing 315 CFM @ .700 with a matched super victor. Comp Cams but I can't remember all the numbers. Lift is .704 (I) and .6XX (E), 14.5:1 comp and a 950 CFM 4150. T/S 5400 stall T400 with brake 4:56 and 29-11.5 Q.T.P. Suspension is 90/10 front shocks with Moroso trick springs and rears are 50/50 with Moroso trick springs and South side lowers and adjustable uppers and a 1.250" anti-roll bar. I run 10.5 psi in the tires because just about anything else and they want to spin. I launch the car @ 3800 off the two step because anything higher kills the tires also. I've tried playing with pinion angle but haven't had any luck with that.Any advice will be taken into absolute consideration. I know I really can't expect too much improvement given that I do run it at Trails but it seems like everything I have tried as of yet has negative results.
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Those aren't terrible 60's, but there is room for improvement. What are the control arm bushings? Are they solid? Are the lowers adjustable? I'm no expert, but I am trying to learn from other guys that are getting it done with 4-link setups. From the videos it looks like the car plants the tires well and stays flat, which is a great start. Have you run an actual slick and not the "street" slick?

A lot of the guys I know that run pure slicks pick up a tenth to a tenth and a half in the 60' from going to slicks over the street versions. This is with stick cars, but maybe that would make a difference.

Guys like Ray and the like would be great to talk to about suspension too, as they have it working well.

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Does the car have a ani-roll bar or at least an upgraded sway bar? I listenen to Patrick Barnhill as much as I can when he talks setup, and he talks about the importance of the anti-roll bar on a radial tire car (or any race car).

 

You car does not do the g-body shuffle to bad, yet, but the second you really put the power down its going to be hiking only one wheel really high, twisting the car. When it twists the car you are only really planting one full time and unloading the other.

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Dave-I have not tried a full on slick on the car yet. I wouldn't be apposed to it if only I could fit something similar in size to what I'm running now. The Cutlass has a fairly narrow rear wheel tub. I have to be carefull what the section width is and on the full race slicks the section width is wider than the street slicks. The control arm bushings on the uppers are urathane at the housing and heim joints at the frame and the lowers are solid front and rear without any adjustments. I talked to a friend here and he suggested running tubes in my rear tires to help with deflection.

 

Waggs-Yes sir I do have an anti-roll bar. I put one years ago and the difference it made was amazing. It really did level the car out off the line.

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Dave-I have not tried a full on slick on the car yet. I wouldn't be apposed to it if only I could fit something similar in size to what I'm running now. The Cutlass has a fairly narrow rear wheel tub. I have to be carefull what the section width is and on the full race slicks the section width is wider than the street slicks. The control arm bushings on the uppers are urathane at the housing and heim joints at the frame and the lowers are solid front and rear without any adjustments. I talked to a friend here and he suggested running tubes in my rear tires to help with deflection.

 

Waggs-Yes sir I do have an anti-roll bar. I put one years ago and the difference it made was amazing. It really did level the car out off the line.

 

Call up Team Z and get their stuff. Dave is a great guy and will help you out with setup.

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What kind of radials are you running? Unless its a Mt pro I'd say 10.5 is actually to low.

 

He is runing the quick time pros, which are hoosiers "street" slick.

George,

Where is your pinion angle? ever thought about trying a 70/30 up front? I think you could hit the pure slick a little harder and see slightly better 60s. when is the last time you checked the urethane bushings? they might be going south too. I've done it and seen it too. ugly mess. basically the pin floating around in a squishy mess of leftover urethane.

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I'd have to check it again to make sure but I'm pretty sure is about 9 or 10 degrees down. In the first video at the 36 second mark you can see it hits the tires pretty hard. I would say from that video that my PSI is too low but when I run 11 or higher it spins terrible. I've tried going 1/2 turn shorter on the upper control arms but it didn't like that and turn a terrible 60. I'd love to be able to give it all on the line and come off just under the converter stall but that gives me 60's in1.5x's. I've never really given any thought to changing the front shocks. I have considered a limiter of short to keep the front from throwing itself up so to speak.
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I'd have to check it again to make sure but I'm pretty sure is about 9 or 10 degrees down. In the first video at the 36 second mark you can see it hits the tires pretty hard. I would say from that video that my PSI is too low but when I run 11 or higher it spins terrible. I've tried going 1/2 turn shorter on the upper control arms but it didn't like that and turn a terrible 60. I'd love to be able to give it all on the line and come off just under the converter stall but that gives me 60's in1.5x's. I've never really given any thought to changing the front shocks. I have considered a limiter of short to keep the front from throwing itself up so to speak.

 

I think you should try a slick and bring it up on the converter before you change too much. just get under the back of the car and check the bushings and mounting points first. If you want to get it to hook harder on the current tires, it will need some tweaking.

The changing of the upper arm length is what changes your pinion angle. did you set up the suspension with you in the drivers seat, or someone close in weight? that is key too.

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