Rear control arm bracing really needed?

[81_El_Homewrecker]

Hey guys,

After installing an 8.8 in my El Camino, I have been working towards resolving a wheel hop issue. I have spherical ends on both sides of the uppers and new rubbers on the lowers that I boxed yesterday. I just received my relocation buckets in the mail to fix the instant center since it is currently behind the car somewhere haha. This should take care of the wheel hop. My question is, I see all this frame reinforcement stuff but have never seen a picture of a mount failed. Does it ever happen or is it hear say? Obviously the manufactures love this idea since they are charging $100 for CNC plate that's folded and drilled. The only thing I plan on doing is welding in washers to the uppers like pontiacgp recommend.

 

[pontiacgp]

read this and there is nothing about upgrading the frame to make a 10 sec GN

http://www.gnttype.org/techarea/recipes/recipe.html

 

[81_El_Homewrecker]

Great read! Then why are Gbody guys bracing their cars to death?! I used poly body bushings and in theory that should allow the entire are to function as a brace for the frame...

 

[GuysMonteSS]

Heres my 2 cents worth.
Several years ago while on the hoist at my buddy's shop we noticed a crack in the crossmember above the rear axle.
I drilled a small hole in each end of it and my buddy welded it up.
Then I installed a set of Hotchkis rear control arm braces;
http://www.summitracing.com/int/parts/hss-1401
There has been no more cracks since doing this.
I have extra braces on my Monte and they sure have helped to tighten the old girl up.
If they didn't work the factory wouldn't have put them on the Pontiac GP,which is where some of mine came from.
Guy

 

[Clone TIE Pilot]

A guy on Turbobuick.com named Charles Long had stock LCA mounts rip off the frame and pierced his floor board. It happened while he was street driving too.

Back in the 60s and 70s, A bodies with big blocks also got factory LCA bracing. They stopped adding bracing with the downsized metric frames.

 

[81_El_Homewrecker]

So it's mostly an issue when running big hp and sticky tires?

 

[pontiacgp]

So it's mostly an issue when running big hp and sticky tires?

it's probably more like lousy factory welds on the frame

 

[Clone TIE Pilot]

So it's mostly an issue when running big hp and sticky tires?

That is part of it along with less than steller welding and a weak design. The other factor is running boxed arms and poly bushings. The factory arms and rubber bushings are designed to flex to prevent binding as 4-links require flexing. When you use boxed arms and non-roto poly bushings, you transfer the twisting to the LCA mounts which are not designed to twist, so they can fatigue and break especially with high power output. Charles was running aftermarket arms when his mounts ripped.

The suspensions in these cars aren't designed for performance, they were designed for rider comfort first and foremost which leads to limitations.

 

[pontiacgp]

If you use boxed upper the uppers give out before the structure welded to the frame. The frame is 14 gauge along with the brackets welded to the frames for the control arms. If a weld is done properly that section is stronger than the metal. I would like to see an instance where the bolts tore through the 14 gauge metal. Here is picture of the elongated 1/2" hole from a stock upper that had been boxed which prevented the upper from twisting when in a bind. I run UMI conversion uppers with a joint on one side to prevent binding

 

[81_El_Homewrecker]

That's why I was asking cuz I find it hard to believe...Following your recommendations from previous threads I boxed my lowers and installed new rubber in both ends. My uppers have spherical bushings on both ends.