Googling for a specific car, I see bolt in and weld in, I'm assuming weld in is preferred. But also on the same page are images of frames being connected under the car but also crisscross bracing inside the floor pan. Torque box?
Googling for a specific car, I see bolt in and weld in, I'm assuming weld in is preferred. But also on the same page are images of frames being connected under the car but also crisscross bracing inside the floor pan. Torque box?
Looks like he is going a bit overboard with the X bracing to the rocker panels on that Falcon.
Anything helps when the entire chassis is like a wet noodle. Last fall I fabricated some for a 62 Plymouth Fury out of .093 wall 1.5x3 rectangle tubing that was a strait short from rear frame to front frame. It took inches of flex out of the car when jacking up one corner! Weld in will add more rigidity and the more places it ties in (like your top photo through the floor and cross member) the better it will work. Makes it more complicated too. Depending on what existing "good" structure you have to work with would be the determination for me about using rectangle, square or round tube. .125 wall thickness would be the maximum I would use as the existing frame/subframe/unibody is likely thinner anyway.
When you connect two flimsy, thin AF pieces of fake frame on an old unibody like a 'Stang or a Falcon or a Nova (etc.), you get a bit better resistance to longitudinal bending, which is generally not the world's greatest hindrance to handling. That's about it, however much aftermarket people would like you to think otherwise at ridiculous prices. Bolt-ins are made for ease of sale (expanding buying audience), not function. If welding is not involved, there is scarcely a point. This has been researched and written about at length elsewhere (perhaps Corner-Carvers, if that still exists).
Some engineers here might make some good points regarding the concept of beam; the closest most cars will get to a beam, at least a localized version, is in the rockers, which is ironically not where subframe connectors are focused. In other words, nobody would buy them if huge sections of floor pan had to go away. Nevertheless, wider and/or taller beam is what will help one avoid the twist (making suspension work better), in addition to cross-body support . . .
Properly placed and applied, a bit of 2x2 square (.095) tubing can do wonders. Just ask the GT1 designers.
Before the install, place a jack under the front a-arm and see how far the front tire rises before the rear on the same side comes off the ground. Repeat after the frame connector install to see if it made a difference.
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