CONTROL ARM BRACES: Don't leave home without'em

here's a picture installed on my 64 with 2 1/2" exhaust

Bruce

 

UMI's fit with mt 3" TA tailpipes. The have a slight bend and some adjustment to them.

 

slight bend as in, that's how they were designed or as in you slightly bent them to work with youre application..

I'll be running 3in pypes exchange so, this'll prepare me

 

http://www.umiperformance.com/catalog/index.php?main_page=product_info&cPath=2_173&products_id=286

 

thanks alot kick

 

These braces not only hold the upper arm crossmember firm, they help support the lower arm front bracket as well. Thats the one that rams up into the trunk area on big HP applications.
More chassis info here.
http://www.v8buick.com/showthread.php?t=213538

 

Ok, I think I actually do have them. I thought they were on the rear side of the cross member though for some reason on my car, but must be on the front side.

 

Edelbrock vs UMI...
I like the Edelbrock design better, less dependence on the bolts, and less likely to move around during use. Opinions?

 

The slotted ends can slip on a hard launch and make a creaking-tearing noise that will scare the s*** out of you.

The tubular ends with more bolt length inside just need to be torqued to spec and have HIGH GRADE bolts.

 

Are these just for you a-body guys??? Won't boxing the rear arms on the big -bodied cars do the same thing?o No:

 

poppaluv

The brace, along with the contol arms, makes a sort of triangle.

Bolt #1 is below the axle and holds the lower control arm.
Bolt #2 holds the front of the lower control arm to the frame. Attatch the brace here on this same bolt.
Bolt #3 is at the upper cross member and holds the front of the upper arm AND the other end of our brace; together on ths same bolt.
Bolt #4 is at the top of the differential and holds the back of the upper control arm.

Don't know if these are available or even needed on the big Buick frames. They could be fabricated if needed. Ask www.hrpartsnstuff.com

ALL stamped steel control arms can, and should be boxed. But, the lower arms are most vulnerable to flex failures.

 

Thanks Gary!

I'll keep this in mind when I finally adopt a 'Lark!!! :beer

 

Good point Gary.
I would think the UMI bars would cause the bolts to flex under use, eventually leading to bolt failure. That would be ugly.
You could weld some washers onto the E-brocks's slotted ends so they don't move around.... (after determining exact mounting position of course).

 

My 72 GS 350 auto had them on from the factory,i also box the stock uppers.I really like what bob g does also !

 

Tagging along...

 

After looking at both designs, I think that each has their strengths. The Edelbrock design is such that it would have less torsional deflection at the upper control arm attaching point while the UMI design has a better length adjustment mechanism and design with no chance of slippage.

What I don't know is the actual loads these will have to endure. It may be a case where the loads are no where near the level that would cause torsional deflection problems for the particular fastener size and strength that the UMI set up uses at the upper control arm attaching point. If this is the case, then I would buy the UMI and never give it another thought. And, I suspect this may be the case.

An easy fix with the Edelbrock might be to weld in the slotted holes and then drill a hole in the exact length/location that you need. Once this is done, I would feel like I had the perfect solution. If I wanted to get really trick with the Edelbrocks, I would weld in and re-drill a single hole on each side, and then: cut, thread and install a jamb nut like the UMI uses to adjust the length. But, then again, I could always make a simple job into a project when over-thinking it enough:laugh:

 

I "assume" the long bolt can't deflect when the opposing pressures are seperated only by only a few thousandths of an inch.. The bolt is held solidly on each side of the mount, and the UMI tubular section keeps the opposing pressure spread evenly against the rest of bolt. The bolt sees no bending stresses.
This is similar to a heim joint with a bolt going through the eye and into a mount. Firm mount on one side, and just a bolt head on the other side. Looks scary.
UMI has to carry product liability insurance, and they must protect their reputation as well.
I would trust this product for myself. GB

 

I have to disagree on this one. The thrust angle on the lower connection limits the bending stresses but the upper control arm bolt clearly has a thrust center that is an inch away from the connection point. This will most certainly create a torsional fulcrum and introduce side deflection. The only question is if it is significant to have any long term cycle stress effects on the fastener.

This is the whole beauty of the Edelbrock system. Because it uses a thin plate mounting connection, there is no additional leverage added to bend the bolt at the upper control arm mounting point.

 

Hotchkis makes the same thing.
BMR makes the same thing and the specs are:
1" X .156 tubing This is some tough stuff.

If the bolt and tube have a snug fit, the brace would have to absorb any flex with the bolt.
Can't imagine this being a faulty part anyway.
BMR, Hotchkis, and UMI have been around a while.

My upper adjustable UMI arms are heavy and built like CAT crawler tracks.

 

I would be willing to bet they are over engineered. Like I said. I am fully capable of over-thinking these things.