8 second OEM 4 link drag race chassis setup

[Alky V6]

This thread will entail my chassis setup adventure. Descriptions and pictures of the front and rear hardware can be found in the fabrication section.
I'll start off with a pic of the front coil over shocks adjustment that was necessary to obtain preliminary 1/16" higher ride height of the left front. Yes, the frame is definitely tweaked.

The first pic is the left front.

 

[novaderrik]

your car has factory installed coil over shocks?

 

[Alky V6]

your car has factory installed coil over shocks?

No, most of the factory suspension components have been upgraded. The car still retains the factory 4 link arrangement in the rear.

 

[charlief1]

your car has factory installed coil over shocks?

LOL You need to look up his other post. He just got the QA1 set up. Subscribed Donnie.:biggrin:

 

[novaderrik]

LOL You need to look up his other post. He just got the QA1 set up. Subscribed Donnie.:biggrin:

well, then the "oem" label is a bit misleading..

 

[KEVINS]

This should be a kewl thread!!

KS

 

[Alky V6]

well, then the "oem" label is a bit misleading..

Sorry about the perceived false advertising. I should have stated, OEM style suspension.

 

[Alky V6]

This should be a kewl thread!!

KS

I was hoping you'd like it. From what I have heard, there are those that are into the 7s with an OEM style 4 link suspension. I'm not looking for 7s, but mid eights is a reasonable target for my current powertrain and pocketbook. I'll be measuring out all the pickup points of the rear suspension and posting them. Then it'll be time for weight scales to figure out weight distribution and the center of gravity point.

Kevin, be kind to this rookie. I'm hoping you'll keep things on the right track. I've been to your site. Very good study. I'm hoping that I will apply what I've learned up to this point correctly here in this thread.

 

[KEVINS]

I was hoping you'd like it. From what I have heard, there are those that are into the 7s with an OEM style 4 link suspension. I'm not looking for 7s, but mid eights is a reasonable target for my current powertrain and pocketbook. I'll be measuring out all the pickup points of the rear suspension and posting them. Then it'll be time for weight scales to figure out weight distribution and the center of gravity point.

Kevin, be kind to this rookie. I'm hoping you'll keep things on the right track. I've been to your site. Very good study. I'm hoping that I will apply what I've learned up to this point correctly here in this thread.

I'll be around and answer any questions you have. When a car starts going that fast they are dangerously fast and I want to make sure things are safe so feel free to email me or ?? if you have questions. It's always good to make sure that everything is set up right to begin with so you have enough adjustability for tuning it later.

ks

 

[Alky V6]

Here are my chassis suspension points and measurements up to this point.

Wheelbase: 108"
Percent weight on rear: 43%
Car weight: 3140 lbs. w/driver

Rear tire diameter: 29.5"
Front tire diameter: 26"
Pinion yoke angle: -1.5 degrees
Driveshaft angle: -2.0 degrees
Trans output shaft angle: -2.5 degrees

Top axle bracket: 0 x 20.81"
Bottom axle bracket: 0 x 10.56"
Top chassis bracket: 7.5" x 19.94"
Bottom chassis bracket: 19" x 11.5"

Instant center length: 61.9"
Instant center height: 13.6"
Anti-squat: 104.2% Using an estimated 22.79" CG location.

The height from the floor to the middle of the front lower control arm bolt is 9.125". Floor to front crossmember clearance is 6 7/8".

I suppose next will be to level out a floor area and search out some scales.

 

[Otto J]

The right words are "stock style supspension"

 

[Alky V6]

The right words are "stock style supspension"

Thank you, Otto.

 

[Alky V6]

Here's a pic of the front lower control arm with the ride height that I picked for the front end.

Is it preferred to have the lower control arm parallel to the ground?

Front end extension travel has been limited to 2.5" to 3". The stock rubber bumper actually starts to take on the load of the spring and tire/wheel about 1" sooner.

 

[KEVINS]

Don,
You're probably going to want the IC around 34"-38" with around 100% AS with the LCA's perfectly horizontal with the ground. The IC is pretty long right now and may not load the tires hard enough and keep them planted. It's not too bad right now if you can't get it moved back, tho.

Since you have the frontend tied down the tires won't have too much bumpsteer so I think your front arms should be fine.

KS

 

[Alky V6]

Don,
You're probably going to want the IC around 34"-38" with around 100% AS with the LCA's perfectly horizontal with the ground. The IC is pretty long right now and may not load the tires hard enough and keep them planted. It's not too bad right now if you can't get it moved back, tho.

Since you have the frontend tied down the tires won't have too much bumpsteer so I think your front arms should be fine.

KS

Thanks for the feedback. If it was easy to get the IC as you described, I'd do it in a heart beat. I'm sure you understand the difficulty with the 'stock style suspension'. We'll see how she does as it is.

The bumpsteer issue was one of the main reasons for limiting travel. Thanks for confirming.

 

[novaderrik]

The right words are "stock style supspension"

even with coil over springs?

 

[charlief1]

Cool Donnie. I thought this would be an interesting thread. I like the idea of the limit straps but since I'm a street car I'll need to find a way to disconnect them for driving home.

 

[Alky V6]

Cool Donnie. I thought this would be an interesting thread. I like the idea of the limit straps but since I'm a street car I'll need to find a way to disconnect them for driving home.

I didn't use straps. In fact, you can't really see anything limiting the travel.
The pad on the frame that the stock rubber bumper hits, I drilled a bolt hole off to the side of where the bumper hits. I then fabbed up an aluminum block that I bolted to the stock pad. By changing the height of the aluminum block, I can change the amount of free travel. One thing to remember though. The rubber bumper does compress a lot. So there might be 1 inch of true free travel, but another inch and a half of travel as the bumper is compressing. It does give you a soft limiting though. The amount of free travel with the stock setup is over 5+ inches.

 

[Alky V6]

Thanks for the feedback. If it was easy to get the IC as you described, I'd do it in a heart beat. I'm sure you understand the difficulty with the 'stock style suspension'. We'll see how she does as it is.

The bumpsteer issue was one of the main reasons for limiting travel. Thanks for confirming.

I'm using the Moser 12 bolt housing, by the way. I'm sure you know of the raised UCA mounting. I think the LCA mounting location is a little different also.

 

[turbobuick]

My suspension plot

Here is the suspension plot we did on my car in 2006 using the info on Kevins site. The UCA length is marked wrong this wasn't the final version but I believe the calculations are correct. This was with a 29.5" tire. Car works better with a 28" tire which calms down the front end and doesn't allow the car to wheelie as much.