Rear UCA, A-body. Curretrac or Edelbrock? Johnny joint = Spherical ball?

[64Chevelle]

Hi,



are the Curretrac rear UCA's Johnny joint the same thing as the Edelbrock's (part# 5249) spherical ball assembly???

I understand the big advantage of the upper arms, but how much do the lower arms (curretrac w/Johnny joints) help avoid bind? If I use the stock LCA's with the Curretrac uppers, will it be almost as good? Or perhaps I could just buy the Johnny joints and mount in my stock control arms? Suicide Doors, got some, they don't call it Johnny joints though.

Also, should I use any kind of mounting relocation brackets to improve the roll height?

[jackfrost]

aftermarket lower arms are usually much stronger than the stock arms, even boxed stock arms. bind becomes a problem when you use stiffer-than-rubber bushings, because the rubber allows a certain amount of articulation that a stiffer bushing wouldn't. the johnny joints/spherical ends/heim joints all add back some articulation.

also, relocation brackets are only needed if you have lowered the car and/or you're having traction problems.

[Norm Peterson]

There are a couple of handling implications of axle side LCA relocation brackets in a triangulated 4-link suspension. The roll center does move, very slightly upward. Axle roll steer is reduced and is likely a much bigger effect. Carefully chosen (and minor) pivot relocation here would dial out some of the understeer.

Raising the axle side UCA pivots (Hop-Stop bars) pushes the roll center up significantly and drives the axle steer further into vehicle roll understeer (neither of those effects are particularly good for anything that turns corners with any enthusiasm).

As far as traction is concerned, the lower arm bushings have a greater effect than bushings in the uppers (the lowers are loaded more heavily during acceleration).


Norm

[64Chevelle]

Great explanations and pretty much a confirmation of what I already knew from searching the forums. But I still don't know if the Edelbrock Spherical ball assembly is the same as the Curretrac Johnny joints... I've read some disfavorable things about Spherical bushings in the forum and I'm not sure if that is the same as what Edelbrock is using or if Edelbrock is in fact using Johnny joints. Any clues?

[jackfrost]

i'm guessing here, but I would say "Johnny Joint" is Currie's brand name for spherical bushings, whereas Edelbrock has their own.

I believe the disfavor for some spherical bearings or heim joints is because they are harsh and wear quickly. supposedly the Johnny Joint has solved these issues to some degree.

[MrQuick]

Actually the Edelbrocks use the Rubicon joint. It has an adjustible ball cap. Same deal though. Sealed greasable spherical.

[Chewy72ss]

Would it be beneficial at all to use "Johnny Joints" at all ends of a fabricated 3/4 link??

[Marcus SC&C]

Some kind of greasable urethane or delrin race spherical bearing one at least one end of each arm is a big benefit.The Edelbrocks are copys of the Curries,there are other manufacturers making similar parts as well. Currie holds the original patents,the others just change them a little. We`ve used both the Currie and Edelbrock arms over the years and both will get the job done but the Currie`s are MUCH more beefy,especially on the axle side. I wouldn`t use the Edelbrocks on a serious high horsepower car. Johnny Joints have slightly better NVH characteristics than the Edelbrock joints.
A Johnny joint (or similar) is most critical in the upper arms but they help in the lowers as well. They give the arms less longitudinal compliance than typical bushings so the rear axle is located more precisely. Rigid lower arms (more rigid than stock) are helpful under hard acceleration because the lower arms are in compression (they actually push the car forward). If they flex the car can unload/load/unload the suspension and wheelhop. The upper arms are in tension under hard acceleration but do most of the lateral axle locating duty. There`d be nothing wrong with having Johnny Joints are all locations in the rear arms but because we`re only dealing with a few degrees of total articulation in road cars (vs OFF road ie. 4x4) they`re not really necessary. Mark SC&C

[64Chevelle]

I've chosen the Currie ones and just placed an order with Marcus. I can't wait to get those arms mounted (and the rest of the suspension for that matter). The alu. rear arms look great too. I believe the polygraphite bushings will give a fast reacting suspension, I have plain poly bushings in the front LCA's now and I notice the suspension reacts too slowly over larger bumps.

[jackfrost]

you might want to take a look at Del-A-Lum's for the front suspension.

[64Chevelle]

you might want to take a look at Del-A-Lum's for the front suspension.

Absolutely, I'm swapping my stock LCA with poly bushings with the new SC&C LCA's with delrin (pretty much the same as Del-A-Lum's I believe) bushings.