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Discussion Starter #1
How important are they? I cut both of mine out when installing my floor pans because a bunch of water collected there from trapping between the box plate and my frame rail. See here.


How strong do I need to make this part of my suspension? Right now I have a stock 351W 4bl, C5 shift kit, and 2.73 gear. I'm about to install some sub frame connectors and slappers on the rear. I just didn't know how much (if at all) my frame rail is going to want to twist in the front. If so, how would no torque box affect the front frame rails on a mild test drive around the block?

Or do I need them at all?






MoocH
 

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Well, it's well known that the Mustang's unibody structure is a bit lacking in integrity to start with. I'm positive that leaving these out is a bad idea.
What passes for a Mustang's "frame" is the front frame rails which are joined to the rocker panels by the torque boxes. The rear frame rails also attach to the rockers with torque boxes.
If you leave out the front boxes, there's no connection between the front frame rails to the rockers except the firewall and floor pans. Ford did just that on the earlier Mustangs but when they added engines such as the 1967 390 that produced a lot of torque, they discovered they needed a bit more substance in the frame department. For the same reason many 65-7 owners will fit their cars with aftermarket torque boxes. My 67 came only with a driver's side (normal for 67 six cylinder cars). After redoing the floor pans I wasted no time putting in a passenger side torque box as the six cylinder will be replaced be a 351W.
Since the 351W will be fed by a pair of turbos, I also put in homemade subframe connectors mated to a Total Control X-brace. Topped off by an 8-point rollcage. My car no longer perceptibly flexes or has "cowl shake" at speed.
 

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Discussion Starter #3
That's about what I was thinking. I have a 351W HO stock with a C5 auto/shift kit. I have a set of subframe and am about to get my 8pt roll cage from summit.

I'd like to use a stiffer replacement for the torque boxes in the front. Any ideas? Round bar? Square tubing? Thickness? Should I cut a joint in the frame and rockers?

Thanks for the info Gypsy.





MoocH
 

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Old Mustangs are to hotrods!
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Heck, mooch they are there to help with the twisting that those dangstamped steel machines do! I believe they even transfer some of the torque into the fire wall and dash, since it's all welded together there.

I replaced mine . And I'd say you should do the same. I also boxed my front floor supports/rails before I put the new floors on. I also ran a plate ( 1/8 about 15 x 6 inches) from the rocker panel to the support/rail on top of the floor to tie it together. Then my front bars for the roll bar are attached to that plate.
Over kill probably, but yeah well I had the welder in my hand......
 

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"Overkill, probably" -heh heh, I could name my car that. In my case the main hoop of my rollbar has two "inner braces". I designed my subframes so these two braces would go through the floorpan (sort of) and weld directly to the subframes. Sort of, because the subs are right up against the floorpan anyway.
Back on topic. I would (and have) just replace the torque boxes. They work. Their strength isn't in the amount of steel in them, but in their geometric shape. It would be tough to match their strength with anything homemade with out ending up with some very heavy pieces in there. On the plus side, they're not at all bad to replace if you haven't mucked up the floorpans too much. Ahem. I had to "adjust" my toepan a bit (with a BIG hammer). Some folks claim to be able to stick the boxes right in, others (like me) have had to split them in half. This is just popping the manufacturer's spot welds, putting both both pieces in and then rewelding.
If you've done floor pans, torque boxes are no big deal at all by comparison. When I bought mine from NPD, I asked about the cheaper versions. The counter guy flat said "you don't want those". So I got the slightly more expensive ones and they worked just fine. I have no idea what's with the cheaper versions but given my experience with other cheapo repop parts the counter guy didn't have to tell me twice.
 
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