GSE guys, how about some Chassis advice?

First off, I don't plan on running this class (GSE), but the setup I have will be somewhat similar to this type of car, with less power, so I thought you GSE guys would be the ones to ask.
What do I need to do to my 69 to hook it up, as far as the chassis goes? The motor will be making probably 550-575hp, I have a 3500-4000 stall converter, and 4.11 gears. Since the 69's can't fit much of a tire, what will help me put the power down in a full weight 69? My original plan was to box the control arms and run some airbags, but now I don't know if that will do it (the original plan was for less motor). Can anyone give me some details on what you are doing with your car's suspension?

 

Greetings from Team Headless Chicken.
We've raced a '70 GS455 for 12 years. Mild 455 (500hp or so) with boxed control arms, air bags and no-hop bars.
Car launches straight. We run 18 lbs in right rear, 8lbs in left. Front suspension includes Moroso ss springs and Comp. Eng shocks, 80-20 left, 90-10 right. I highly recommend the air bags.

 

Forgot to mention: 4.11 gears, 30x 10.5 tires and a best 60' of 1.52 seconds (average 1.55(

 

Thanks for the info, Clark. Not everyone seems to be so open-mouthed on this topic (could be a lot of competition I guess). I am going to try and put down 575hp in a '69. Unfortunately, it looks like a 9" tire is about all I can fit. I have a feeling it might be a wild ride I'm seriously considering mini-tubbing the car to get a 10-1/2 or 11 under it, but that is a whole lot of work, and I'd like to have this thing ready to go pretty soon. Maybe this year I'll go with a setup similar to yours, and see what happens. Thanks for the help.

 

I think that the 9" tire, while a challenge, will not be impossible to hook. Boxing the lowers, getting some weight transfer from the front via moroso springs and 90/10 shocks, and some adjustable upper rear control arms to set pinion angle. A good rear anti-roll bar will help!

 

Jeff,
That's good news... I'm really pretty worried about making this work, more for safety than anything else (Don't want to put the car into the wall). I hadn't planned on building this much motor, and I'm starting to think it might have been a mistake.
What's the deal with the pinion angle? Is there a general rule to go by?
Considering the advice above, here's what I'm thinking about:
boxed lowers, adjustable uppers, hrpartsnstuff anti-roll bar, airbags, Moroso front springs, 90/10's front. This will be with (hopefully) a 29" tall X 9" tire (I'm not sure if I can fit a 29" tall tire... might end up being a 28").
Sound like a good plan?

 

Steve,

I've run tires as big as 10.5x29. I think I have 12.5" from the lip to the frame, any tire with a section width of 11.5" or smaller will work for me. Just make sure your wheel centers the tire in the space you have.

Also if you run the anti-roll bar, then ditch the air bags. You will not need them, and besides they don't let your springs move right. I think air bags work great until you get into the low 11's or 60's less than about 1.55. Don't get me wrong, they'll still work, but there are better choices when you get that fast. The anti-roll bar is much better in my opinion.

good luck

 

Shayne,
What rear end do you have under your car, and what wheels are you using on the rear (and what backspacing)? I have a 12 bolt out of a 68-72 Chevelle. Did you roll your fender lips?
My thinking on the airbags was to get the ride height up a little to fit the taller tires, but if you are saying you can get a 29" under there, then that would work for me. What springs do you have in the rear?

 

I'm running a 12 bolt, however it's been shortened a little (don't remember how much, around 1.25" ea side). So my 8.5" wheels have a backspacing of 3.375" and wouldn't work on any other GS. The deep dish looks cool though.

My wheel well lip hasn't been rolled, but has been trimmed a little.

My springs a pretty stiff. I'd like to try a little softer spring as a test. I'll try and remember to look at the box tonight and get the number for you. Remind me if I forget.

I used to run air bags before I installed an anti roll bar. With as little as 10 lbs of air, it would make my rear suspension almost solid, like a dragster.

 

Thanks for the info. Maybe the stiffer springs are helping you out, as far as the clearance goes. I need to get under the car and start taking a bunch of measurements. It would be nice to be able to fit even a 10" slick under there.

 

Steve, I know its different on the 68-9's, but I use a 29x10 Hoosier on my 70GS. 1970 (C) 12-bolt, 15x8.5 wheels with 4 7/8" backspacing, and there is LOTS of room! Maybe you can borrow someone's wheels and tires to trial fit? Anyone close to you that has 10" tires?

I'll agree with and defer to Shane's advice on the airbags vs antiroll bar. You are past airbags now, I think.

I think about 2*, but that's debateable.o No:

 

Steve, here's what I have.

Stock front suspension. 90-10 shocks, lowered the front end by cutting a bit off the springs, G$CA street/strip springs front & rear.No sway bar. The upper and lower a-frames are loosened/freed up so with the spindle off the car, they drop freely.

Rear suspension. adjustable shocks, usually set as soft as they go, poly bushings with stock upper arms, "Southside Machine" style (don't ask for the exact name or manufacturer because I truly don't know---long story but these parts are from years ago)lower arms. Nothin' special at all.No anti roll bar. Air bags, usually 0-5lbs for the drivers side and around 20 lbs for the passenger side.

9" tires. Don't even think that you need a bigger tire than a 9".
Most of us(GSE) run a 9"X30" Hoosier radial slick. I have gone 1.37 60' @ #3825-3840lbs on these tires. These tires are quicker and faster than a same size "wrinkle wall" slick. Tom Rix has gone low 1.30 60's on these tires also, and has gone 9.81 @ #3400 range. Some advice that I wish I would have recieved long ago is to go with a reputable convertor company. Many times guys try to save when buying their conv and end up with one that is to tight. I used Coan.

 

Gary,
Great info, thanks!
I would be willing to bet that the 30" height of that tire is helping out a lot. We have found that even on my dad's car that is running low 12's a taller tire drops the 60' times.
I went with an ATI treemaster and competition TH-400. My dad uses an ATI, and his car launches extremely well, and is very consistent.
Glad to hear that I can do it on 9" tires! I don't think I have the time or skills required at this point to mini-tub it.
Greg Gessler uses the loose front suspension trick too, from what I've read. Is there any safety issue doing this to a car that will be street driven?
What are the benefits of a radial slick? Are these cheater slicks (as in barely legal street tires) or real slicks, but radials?
This car will probably only go low 11's, which is all I want for it. I plan on adjusting the shift points, and maybe how much the throttle opens to keep it around 11.50's.

Thanks for all the help, guys.

 

Steve, the treemaster is the convertor that I used initially but after going through the trouble to send it back 3 times and have it perform no differently each time, I went with Coan and have been happy ever since. Sounds like you are happy with your ATI so thats great.

My friends and I have loosened the front suspension on several street/strip cars and haven't found any problems while driving on the street.

The Hoosier radial slicks are not "cheater" slicks. They are the real deal. Stiffer side wall, and the probability of nearing 25lb air pressure are the benefits. They will hook your car, don't worry. Give Hoosier Tire Midwest (Indiana) a call and talk with their drag slick tech man.

 

Hi, Won't 4.11 gears and 28" tires pull alot of rpm at finish line? I have 29.5-10.5 Mickey Thompson slicks on mine with 4.11 gears and have been thinking of going to 3.73s to kill a little of the bottom end and pull down finish line rpm a little. Tom W

 

Thanks, Gary. I'll look into the Hoosiers. Sound like a good tire.
Tom,
what kind of times are you turning, and what RPM are you pulling through the traps?

 

Steve
Do what you will with this suggestion,But this will make the most sense for you are looking to do.
I'm getting the impression you want to run the Car at less than full potential.....No cage,consistency,easy on parts.
The easiest way to do that would be to run a converter that is too tight.
It would keep the car managable and consistent on small tires w/o wasting money on suspension parts that you don't need.
Box the rear control arms and use new/good bushings and you're done there.On the front,Use stock stuff,done.
If you ever decide to add a roll bar for the sake of going faster,Then you can further address the chassis.
At this point you don't need much in the way of suspension to run mid 11's.With the tight converter and an adequate tire the car will ''drive'' off the line consistently.
My old Green car went low 10's with a motor of similar power to what you're anticipating,So you have planty of potential if you decide to go faster.
A converter that only flashes 2800-3000 would really take care of your worries for tire size,suspension,etc.

 

I want to take a guess at this!:Brow: 11.47 @ 116mph (in his signature!:grin: ) And since he already said earlier that he has 29.5 tires and 4.11 gears....................

5430, assuming 100% torque converter lockup

+5% slippage, about 5800 rpms give or take a hundred.

How close am I?

 

You are pretty close on the RPM, my converter is just a little loose in high gear, The day it ran the 116 MPH about 6000 rpm on my tach and rev limiter was set to 6100 in the ignition box and just hit it right on the line. On a average day it runs about 5800-5900 at the line. With new slicks on a good track I have got a best of 1.52 60ft with a stock front end with just the sway bar removed. Tom W

 

Hmm, more like 8-10% slip then. Yeah that's a little 'loose'.