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Discussion Starter #1
What do you do with the original factory upper control arm bolt holes after completing the Arning drop? Do you weld them shut? Do you install tight fitting bolts? I realize that most people just leave them open, but I’m looking for more answers. My goal here is to reduce a stress concentration at the original factory holes.
 

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I am not an engineer, but we hav3 done the drop on our 65 & 66.
66 done 12 years ago, when we did it we also installed tcp tubular front suspension, 1.25” sway bar, 600lbs springs, Kong’s and polygraphite bushings.
Front end is almost too tight at times.
Bottom line is all of these mods would tend too increase the load on the shock tower and we have not had any fatigue issues at all let alone at the upper a arm to tower mount locations.

Shellby did not add any additional metal or supports as well for what that is worth.

food for thought.

good luck,

Pat
 

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My goal here is to reduce a stress concentration at the original factory holes.
I'm having trouble seeing any stress concentration to speak of there at all. I'd guess most (like me) just leave the holes open, but I've read of some closing them off for purely cosmetic reasons.
 

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Closing the holes is really pointless. They do not significantly weaken the tower, and are almost impossible to see without a flashlight and probably a mirror.
 

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Black plastic plugs or grommets from the hardware store would cover it up and never rust. I wouldn't weld mine up, just in case for some reason I ever decided to put it back.
 
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Sharp edges have stress risers. Holes are actually cut to relieve the stress at those points. From a structural point of view I can't see holes in the middle of a sheet being a stress issue.
 

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Discussion Starter #9
while yes, holes are used as stress relief at the end of cracks per say, that doesn’t mean they aren’t stress risers themselves in a clean sheet of metal. Im just thinking how to better the situation cc
 

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Im putting plastic plugs in to keep anything from splashing into the engine bay. Less cleanup.
 
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while yes, holes are used as stress relief at the end of cracks per say, that doesn’t mean they aren’t stress risers themselves in a clean sheet of metal. Im just thinking how to better the situation cc
OK, but the weld will create a heat affected zone around each hole. I have a couple hundred thousand miles on the holes in my towers, and of course already mentioned is Shelby left them in.
 

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Well my car is a little different. I actually have a flat plate covering all four holes. Two holes are filled via the A arm in the new location and the other two bolts covering the old holes and the plate. The plate also has a thickness to kick the A Arm outboard to improve caster/camber for road racing.
 

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Discussion Starter #17
Well my car is a little different. I actually have a flat plate covering all four holes. Two holes are filled via the A arm in the new location and the other two bolts covering the old holes and the plate. The plate also has a thickness to kick the A Arm outboard to improve caster/camber for road racing.
Hmmm, good idea, I like that
 

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Some comical answers! I welded mine personally, for no reason other than I welded up all unnecessary holes for cosmetic purposes even though you could barely see those ones.
 
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