[killerformula]

Hey all-

So I'm picking up ideas/knowledge here and there about chassis setups. I have the stock suspension in my Formula right now (77) which, surprisingly, is pretty responsive.

The mill I put in (more detail in my journal, 383, ~425 horse or so) is exactly what I wanted for the car. I'm very pleased with it. First thing this next season the car is getting a shift kit and 3.73 gears. Trans is a TH350, 2500 stall.

Problem is I can already turn the tires over pretty good (posi unit) even from a dead stop, no brake torque and granny gears (2.73, currently). I realize this is going to hurt me badly when I do my 1/4 mile passes with the 3.73's. In fact, I'm wondering if I'm going to be able to hook up at all.

So my first plan of action is going to be to put in poly bushings and mounts all over the car, to reduce flex and optimize weight shift. I would consider putting the battery in the trunk, if you all think its worth it.

I think I probably need some traction bars and (sadly) I'm not much of a fabricator. I've seen trac bars for my car anywhere from 20 dollars to 400 dollars a set... where do I start? Keep in mind this isn't a 700 horse motor or anything, and its a street/strip car. I just need something functional.

My other consideration is subframe connectors. Are the benefits realized from these bars going to help me, or is it really just a waste of time to have them on the car for this type of application?

Lastly, I'm also worried about dynamic handling. This thing is still going to be driven on the street, so I won't sacrifice my front sway bar or anything just to make a launch once a month. Can I keep my rear leaf, front coils and sway bars and still be successful? Furthermore, are the body mods (trac bars, subframe connectors) going to hurt my handling through turns my not allowing the body to respond?

lol, why do I always write so much?!

Thanks in advance-

K

 

[Max Keith]

suspension setup

I would recommend going with slightly stiffer springs in the rear, about 100 lb stiffer than what you have, 40/60 shocks, and go with 90/10 shocks on the front. What this will do is to allow your weight to shift faster to the rear, and the 90/10s will keep the front end up longer, allowing longer duration of the weight transfer. The slighly stiffer springs will add more chassis weight to the rear as well. The 40/60 shocks on the rear will also apply more down force on the rear end as the valving on compression is smaller than for extension. Going with the poli bushings will help as well. Since you already have a multi link suspension, rather than leaf springs, Im not sure traction bars will help you as your links already act in that fashion. You dont have any axle wrap as you would with a leaf spring.
Lastly, get some super sticky tires.

Mounting your battery over the right rear wheel will help as well. I would put it over the frame rail and as close to the wheel tub as possible.

be advised that mounting your battery in the trunk will require you to put an external remote battery disconnect switch on the rear of your car, if you are going to run your car at most sanctioned tracks.

 

[BillyShope]

And you don't need to "sacrifice" your front sway bar. Just disconnect it before you run and reconnect it before you head back home. Only takes a couple of minutes.

If you're going to play with shocks, as Max has suggested, I would recommend the 90/10 on the left front ONLY. Why? Well, as the front comes up, the stock shock will tend to unload the right front. Since the sum of right front and right rear loads must remain equal (or the car would be rolling over), that means most of the weight transfer will be going to the right rear, tending to cancel the driveshaft torque effect. (It would be better to have a higher rate spring on the right front, but that's probably beyond what you'd want to do.)

 

[Max Keith]

suspension

Ditto with dropping the sway bar on the front but I would stay with my other recommendations.

 

[killerformula]

Re: suspension setup

Since you already have a multi link suspension, rather than leaf springs, Im not sure traction bars will help you as your links already act in that fashion. You dont have any axle wrap as you would with a leaf spring.
Lastly, get some super sticky tires.

I know this might sound silly, but I honestly don't remember what I saw back there (maybe you just confused me) and the car is sleeping for the winter, but I'm pretty darned sure its got leaf springs back there... 99% of the aftermarket parts for second gen Fbody cars are for leafsprings too...


BTW, are 90/10 shocks going to make normal driving and handling poor?
K

 

[Max Keith]

suspension

OOPS!!!!!!!!!!! I misread. Was thinking it was the Le Mans and Grand Am chassis. The Formula is similar to the Camaro. my apologies.
As for the front end set up, I would still go with the 90/10 uplifts.
Traction bars would be a good thing on the rear.
Since leaf springs have a history of going flat, is it possible that your springs dont have a lot of life left in them, since you are mentioning that you cant hook up as it is now. A 40/60 shock on the rear with smaller compression valving than for extension would help a great deal as well, even on cornering, even to run them on all four corners. The 90/10's I would just install for drag racing rather than street use.

 

[killerformula]

no problem, and thanks for the clarification and great info keith.

Any other modifications worthwhile, or all those mild chassis warm-up's really all I need?

K

 

[Max Keith]

chassis mods

I would start with the most obvious and the ones that will give the most bang for the buck.

I would probably start with the rear springs and traction bars first.

 

[BillyShope]

Sorry. I should have done a better job of explaining why it's necessary to treat the right front differently from the left front. As I do, those of you with oval track experience will recognize this as that which you commonly do while suspension tuning for maximum cornering performance.

Available tire data indicates that tires act essentially the same, whether while cornering or while supplying tractive force (braking or accelerating). This means that both maximum tractive force and maximum cornering force are achieved when a tire pair is equally loaded. An oval track racer has to worry about two tire pairs: Those at the front and those at the rear. Typically, a dragracer only worries about the rear tires. The oval racer attempts to keep the car's center of gravity both as low as possible and as much to the left as possible in order to minimize load differences between inside and outside tires. But, the dragracer has to look elsewhere for his solution.

Now, if the dragracer is running an independent rear suspension, there really isn't any problem. If the rear tires are essentially equally loaded when the car is at rest, they remain so during launch. But, far more commonly, the car has a beam rear axle, meaning that driveshaft torque tends to unload the right rear during launch. This is the problem for which a solution is required if the maximum tractive effort is to be achieved.

Consider the drag car as it launches. Now, consider the loadings on those four tire patches as you rotate your driver's seat ninety degrees clockwise. You're now looking out the passenger's side window. Imagine, now, that you're no longer in a drag car, but in an oval track car. (Okay, you're straining your imagination, but stick with me on this for a while longer.) That right rear tire patch on the drag car has now become the right front of the oval car. And, as loadings go, it's not doing its job! It's too light and, as an oval racer would say, the car is probably very loose. So, what does an oval racer do to tighten a car? Why, he increases the roll stiffness at the front. Only now, as we return to reality and leave our imaginary oval car, the "front" is really the right side of the drag car.

So, to cancel the unloading of the right rear tire of a drag car, we borrow a tuning tip from the roundy-rounders and stiffen the right side of the car. But, why only the front? This is because it's quite possible that the rear springs aren't even "seeing" the launch. In other words, if the car neither squats nor rises on launch, the weight transfer is being carried entirely through the suspension linkage and the rear spring deflection isn't changing. But, you can depend upon the front always rising, so that's the place to make changes.

It might be argued that, with the stiffening of the right side, you wouldn't get as much front end rise and, therefore, weight transfer would not be as great. And, yes, that's quite true, but, again, the tire data indicates that equal (or more equal) rear tire loading is of greater importance than the small increment of weight transfer involved in the difference of front end lift.

Hope this made it a little clearer.

 

[jimfulco]

Herb Adams VSE used to sell modified rear spring brackets (for the front of the leaf springs) that had the cross-bolt moved upwards by about 3/4" or so. This was to increase traction during acceleration (both straight-line or out of a corner) by increasing the anti-squat in the rear suspension. You might be able to modify yours similarly.