malibu suspension question

[Anonymous]

Hey guys, im new to the forum and pretty new to g-body cars and last year i began building a 79 malibu. I am pretty mechanically inclined as i helped build my dads racecar from the ground up, but when it comes to suspension i dont know much especially on standard 4-link cars.

My malibu has a 406 sbc, turbo 350, 4000 stall. Its all stock front susp and still has the stock 7.5 with an eaton posi and 3.73gears(a moser 9" is on its way) and has edelbrock adjustable uppers and lakewood lower lift bars. stock shocks and springs. Pinion angle is set at -4. I occasionally drive it on the street and its a footbrake car.

I raced our first race last weekend and the car ran [email protected] and was getting 1.56-1.59 60ft times stalling at 2500 (im trying to hold the 7.5 together till the moser gets here).

My question is this.. I know 1.56 is a good 60ft. but when when i stall the car up the front end raises way up, the rear drops a little and when the car leaves it just kinda pushes straight out and there is really no suspension movement off the actual launch. I am wondering if this is normal behavior or if i need some different suspension parts.

Thanks for the help.

 

[cutlass389]

welcome_sign.gif Everything sounds pretty good from here. Do the lift bars lower the attachment point where it connects to the axle housing? I don't have any experience with that style but I run no-hop bars that move the upper arms attachment point upward. When I stall mine up, the rear of the car rises as compared to yours which raises the front. Don't know which is "better" but both change the instant center from stock in different ways. If it's workin' it's cool by me. I 60' around 1.60 footbraking at 1400 with a 3000 stall in a th350 with 3.73's. Very similar. You're making more power than me as I only run 90 mph in the 1/8mi.

 

[Anonymous]

Yea the lift bars have brackets that make them lower than the factory location on the rear end portion. From what i read thats to change the instant center of the car, but like i said i dont know anything about suspension, so thats why i wanted to come ask and get some input from here.

Thanks for the input.

 

[MYMONTECARLO]

I have a 1978 montecarlo w/moser 9", just beware when you install that 9" the housing is bigger than your factory rearend,and the heigth of the upper control arm brackets are taller, so that will change your IC . I had southsides w/ same brackets that your lakewoods have. I would take the brackets off and install in factory hole on lower bracket. I just installed umi dbl. adj. on mine with trying to get lower bar level . you might have to mess with ride heigth,w/ spring to get the best IC. Your system w/9" will be between true stock suspension system and lift bar sytem your running now..

 

[Anonymous]

Any other footbrakers that can share how their car works compared to mine and what suspension parts they have installed?

 

[KEVINS]

It almost sounds like your converter is too tight if it's lifting the nose at 2500rpm. Does it actually flash to 4000?
IMO, a 1.56 is way off if you're running 121 mph. You should be closer to high 1.4's if the converter, etc are right. But you'll have to see what it can do once you get the 9" under it.

Another suspension option that is just about ready to hit the market are these torque box buckets and UCA's that have different mounting holes so the Instant Center may be adjusted for a particular car and rearend. Parts are being zinc plated right now and I hope to have them next week ready to sell.

A pic of the prototype bucket can be seen here and new UCA's are included:
http://www.baselinesuspensions.com/kits/chevy.htm

Kevin

 

[Anonymous]

the converter flashes to about 3600. as far as the 60 ft goes our track here just reopened this year and has all new concrete so it still pretty green. this last weekened i put the exhaust back on and went 11.36@116 and ran a 1.58 60 and was informed it sstill spinning 2 revolutions at about 40 ft out. i wish i had some video ill try to get someone to get some this weekend when i go out for our season opener.

thanks for the help

 

[80montecarlo]

I use the Edelbrock hop stop bars and it completly changed the way my car launches, used to pull the front up and push the a$$ end down. Now the whole car leap frogs like a leaf spring car, I'm also running air bags aswell with all stock control arms, It mad a 0.10 difference in the 60' but I was spinning all the way through to about the 100' mark, wont actually now what the suspension did untill I get the heads back on the car. But from the video and pictures I have from the only 4 passes I made this year what a substansial difference.

 

[cutlass389]

My minimal grasp of IC theory is that you want it about halfway front to rear and below the center of gravity line. If you think about it, when the rear of the car rises at stall load that means that the suspension is separating the axle from the body in essence pushing the tires down into the track. Therefore, if the rear of the car goes down at stall, then I would tend to believe that the suspension is pulling the axle and body together, i.e. if the body is coming down then the axle must be coming up so that the force is not loading the tires as much. Both relocation methods bring the IC rearward(which is good) but differ in the height. The lower bar angled upward will make the IC higher and the upper bar angled downward will make it lower.

 

[KEVINS]

My minimal grasp of IC theory is that you want it about halfway front to rear and below the center of gravity line. If you think about it, when the rear of the car rises at stall load that means that the suspension is separating the axle from the body in essence pushing the tires down into the track. Therefore, if the rear of the car goes down at stall, then I would tend to believe that the suspension is pulling the axle and body together, i.e. if the body is coming down then the axle must be coming up so that the force is not loading the tires as much. Both relocation methods bring the IC rearward(which is good) but differ in the height. The lower bar angled upward will make the IC higher and the upper bar angled downward will make it lower.

I know you simplified where you want the IC a lot but I will explain it a bit more in detail.
You are correct: If the rear of the car is raising up then the rearend is being pushed into the ground BUT the front of the car is also be pushed down.
If the rear of the car is squatting then the rearend is trying to be lifted off the ground (unloading) and the front of the car is trying to be lifted off the ground.

Where you want it is much more complicated than that. When someone is wanting to locate the IC they need to take in account how they want the suspension to react given the weight distribution, transmission, converter, gearing, HP, tires, wheel base, travel, etc..
Simply saying that they want the IC in the middle just is not good enough and can cause more problems if it's not done properly.

The lower bar angled upward will make the IC higher and the upper bar angled downward will make it lower.

Not true. The reason why is b/c the IC position is determined by the UCA angles and the LCA angles. If the UCA's are already angled UPWARDS which a lot already are then angling the LCA's UP brings the IC back and down.
A lot of the rearends in the G-bodies are actually BEHIND the car b/c the UCA's point way UP and the LCA's also point UP but they never intersect in front of the rear axle. So the ride height and control arm angles really should be plotted out to see how it all looks before just tossing on parts for the best performance.

The old way of thinking is racers thought they wanted the rear of the car to raise up during the launches b/c this plants the tires into the ground. But this causes the car to "leap frog" off the starting line instead of simply raising the frontend and transfering weight. The problem with this "leap frogging" is that when the rearend rises this pushes the front end down which can hurt weight transfer. Also, on high HP cars when the rearend is planted into the ground on launch at some point after the launch the rear of the car has to settle back down and when it does this can unload the tires and cause the tires to spin if the car has enough HP. A lot of this motion is determined by the IC placement and is the first thing that I plot and locate before tuning anything else.

hth's
KS