70 Impala rear suspesion

[racer5C]

I need some advice on where to start on my '70 Impala rear suspension. The car is a 600 hp big block daily driver. I want to bracket race with it some so strait line traction is a must, but without sacraficing handeling.
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[homerneedspeed]

hotchkis and PST are the only people i know of that make rear links, panhard bars and sway bars for b-bodies so start there. bilstein are about the only performance shock but since you want straight line handling i would use the more expensive QA1 adjustable shocks. nobody makes aftermarket springs, but yau can use standard 5" dia. springs and adjusters available through Speedway Motors, but again you may not want these for drag racing. if you would like another 70 as a parts car i have one for sale.

[justanova]

nobody makes aftermarket springs,

I got 2" drop springs from pst for my 70 impala, I believe they will do diff. spring rates too.

[Derek69SS]

www.coilsprings.com will do any spring height or rate spring you want.

Does your car have the 4th link, or not? (most had 3-link, but all caprices, BB cars, and F41 equipped cars had 4-link)

unfortunately, your options are pretty limited with that car... there's just not much aftermarket for them.

[Tony@AirRideTech]

there is also a company in El Cajon Ca. called National Spring. From what I understand.... they too can build you a spring for anything.

[racer5C]

It has stock upper and lower trailing arms and a panhard bar, I assume that makes it a 4 link. I need springs bad now cause when I nail it it squats so hard my new 4in aluminum driveshaft rubs the floor. The upper arms are higher in front, I dont know if I can relocate the rear mounts high enough to make arms align for instant center, will trying really help? KYB shocks is all I've upgraded in rear so far (and gears, posi,and battery relocation)

[racer5C]

What is a "3" link? Does my Impala have what is refered to as a factory 4 link or 3? Thought I knew but upper arms are so short I was wondering if thats part of the diffrence.

[Derek69SS]

If there are 2 upper arms, it's a 4-link, and if only one upper arm, it's a 3-link.

I'm not sure about 70, but I know the '65-68 had a 3-link in SB cars, and 4-link in BB cars.

[racer5C]

If I was to completely change the rear suspension or graft in another, what should I consider. I'd like to keep the frame rails but I'm willing to do some floorboard mods for different or aftermarket links and cross-members. I need to be able to run mid 11s at the strip with drag radials but maintain and eventually improve handling with good street tires. I have started on a "easy access bolt in/remove" ladder-bar setup but that's not ultimately my goal. Please share some of your setups with me.

[Norm Peterson]

Got a picture? Even an arrangement that counts four trailing links can function like a 3-link (i.e. plan-view-parallel uppers and a PHB for axle lateral location).

The benefit to the 3-link approach is that you can tune the anti-squat (launch) mostly independently from the rollsteer and roll center height (handling).

I'd avoid using poly in the upper(s).


Norm

[racer5C]

I's a 4-link. I dug out my favorite Car Craft build "Heavy Metal" and they used the stock 3-link in their '65 Impala but said they would later add the missing link to the left side. They managed high 11 quarter mile times with slicks in '91 before the car was stolen. In the illustration it appears that like my car (which needs new springs) the upper link(s) are higher in front and and imaginary lines drawn forward from the upper and lower links would never intersect. If I raise the upper link mount on the rear housing will this affect handling? I cant figure out the logic in the factory link angles but I know they don't plant the tires trying to launch the car.

[Norm Peterson]

In the illustration it appears that like my car (which needs new springs) the upper link(s) are higher in front and imaginary lines drawn forward from the upper and lower links would never intersect. If I raise the upper link mount on the rear housing will this affect handling? I cant figure out the logic in the factory link angles but I know they don't plant the tires trying to launch the car.

If those two uppers are parallel (as I suspect based on PHB’s being mentioned), it will behave pretty much like a 3-link. With that arrangement you have considerable freedom to tinker with the upper link’s inclination without disturbing the rollsteer, as that is determined by the PHB height and the virtual intersection of the lowers.

I doubt that hard launch capability was much of a basic design consideration for those cars, and was likely traded off for gains in ride comfort. If you extend those side view instant center construction lines rearward, they probably intersect at some distance behind the car. That gives pro-squat (aka the poor launch traction) and pro-lift under braking. But since the axle can move rearward slightly under two-wheel bump conditions, less impact and vibration finds its way into the passenger compartment. And pro-lift might also reduce the likelihood of locking the rear drums first in a panic stop.


Norm