[DeTomaso] Engine Bay Brace question

[jderyke at aol.com]

In a message dated 12/20/09 8:26:10 AM, tborcich at msn.com writes:

> My fabricator is building a new adjustable engine bay brace ... I've seen 
> the X or dual type brace and wonder if how important the bottom brace is 
> and what improvements I will notice?
> 
The contribution of a short lower brace just above the subframe rails 
likely won't be noticable. On a street car, it's 'gilding the lily' so-to-speak. 
The typical location is across the area where the upper a-arm attach points 
are located, and I guess the intent is to keep those sheet metal panels from 
flexing. But since the actual a-arm attach point is the 'horse-shoe' 
weldment surrounding the areas where the supposed flex is occurring, and those 
parts don't fatigue-crack or break their spot-welds even on dedicated track 
cars, I doubt if a lower bar does much of anything except add weight and 
complication, except maybe on a real racer driven very hard with gumball tires. 
But if you do decide to add the lower bar anyway, make sure the plates it 
mounts to are curved in two planes to closely match the normal contour of the 
inner fender panels, and are welded or brazed all the way around the 4 
edges. If the mount plates are left flat and force the sheet metal to conform, 
it may break spot welds and cause the situation to ultimately be worse, not 
better. Bolting the plates on won't transfer the supposed loads to the inner 
fender panels as effectively as peripheral welding/brazing. And on the usual 
designs, I'm also not a big fan of welding load-carrying braces to the 
center of the upper bar. Tubes don't like loads coming in at their middles.
My best guess- J Deryke