How much chassis stiffening needed?

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USCT subframe connectors depend on the floor board to make the 4th side of the frame member...
 
Floors front and back and trunk went soft and holy in my 340 A/T 69FB. The first apparent observation something terrible was going wrong was when the leaded seam between the sail panals and roof broke at the top corner of the back window on both sides of the car. Good and proper floors are essential to the torsional strength of the unibody. I repaired the damage and replaced the floors and patched associated rusted frame pieces. In anticipation of a 550 hp BB conversion I then installed fully welded USCT connectors and 4 torque boxes, then upgraded to 1.03" bars. What a difference! The car now has the solidity of a brand new modern vehicle. After pounding on it hard for 2 years there is no sign of damage to any welded seams or the paint finish due to body flexing.
A friend installed the cheap connectors that only bolt and weld into the front and rear frame horns on his 70 CUDA 416,, after a week of spirited driving he had chipped the paint at the 2 rear corners of his doors where they meet the quarter panels. The floor cannot be too strong.
 
You guys are missing the chassis stiffening concept by a lot. The front section of the vehicle is where the engine torque and suspension load is. This is why the reinforcement of the front section using inner fender braces, rad support and under hood brace is so important. These components aren't popular and since we haven't yet come out with an under hood brace, they haven't been used on A bodies. See the photos below of some cracks that developed on my Dart after many track events. These are the driver side inner fender and the firewall areas.

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Projectile Dart said:
I think the factory cars only had torque boxes so I would think that subframe connectors would be stiffer than at least that. But I agree with @toolmanmike with just springing for both subframe connectors and torque boxes, stiffer is better imo
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What I have and dont forget a driveshaft loop!
 
72bluNblu said:
Even the factory did torque boxes on the higher horsepower cars. And they were assuming skinny little bias ply tires. Even the all season radials guys like to run will hook twice as much horsepower as the factory planned for.
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Not sure of the reference Torque box, but the 4-speeds, including the 340's came with a welded plate over the front of the rear springs for extra strength. True, no hook-up, no problem. Hook-up. problem. A little spin is good for a street driven car.
 
I'd get the WHOLE US Cartool kit and a cage if you plan on going quick enough to require one. You're talking about 550HP plus nitrous. That's gettin close to TWICE the power of a stock M code car.
 
Finally got a set of AMD subframe connectors.
Held them up under the driver's side of the car to the frame and the emergency brake line and the stainless front to back brake line are both in the way.
Does anyone have any pictures I can look at or know the correct way to re-route them?
Thanks.
 
You should be able to route the brake line along the side of the USCT connectors. The best solution for the parking brake cable is to notch the subframe connector where the cable passes through and weld a tube into the connector for the cable.
 
I think I just bent the cable guides away from the floor a bit on mine to get the added clearance....I'd have to go look again to be sure. That was many years ago.....
 
At a minimum frame connect the car. If you have really good tires that stick better put some torque boxes in the back if the entire car hooks up very well and has a lot of power time for torque boxes in the front, back ..and frame connectors
 
well we're doing a 70 dart more door with a 440 727 dana , us car tool on the body and firm feel for the k member along with seem welded all the way around .
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I don't know how useful the torque boxes are, I personally don't think much.
Weld-in subframe connectors at a minimum!
For a driver, not expected to be on the track much, a rollbar/cage is a pain in the neck. HOWEVER, if you do have 550hp, and enough suspension to hook it up, you will not be legal to race without one, and certainly not on dragweek!
The alternative is a full cage, tied everywhere possible, including the front suspension towers, BUT, with a removable swing out side bar.
With an added nitrous system, I would use a fixed side bar.
(I tend to have NO respect for guys with obvious mega power...... and no bar or cage. Pro fairground poser!)
With a proper five point harness, used EVERY TIME, and proper nhra legal rollbar padding, I don't wear a helmet on the street.
 
33IMP said:
I don't know how useful the torque boxes are, I personally don't think much.
Weld-in subframe connectors at a minimum!
For a driver, not expected to be on the track much, a rollbar/cage is a pain in the neck. HOWEVER, if you do have 550hp, and enough suspension to hook it up, you will not be legal to race without one, and certainly not on dragweek!
The alternative is a full cage, tied everywhere possible, including the front suspension towers, BUT, with a removable swing out side bar.
With an added nitrous system, I would use a fixed side bar.
(I tend to have NO respect for guys with obvious mega power...... and no bar or cage. Pro fairground poser!)
With a proper five point harness, used EVERY TIME, and proper nhra legal rollbar padding, I don't wear a helmet on the street.
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Just seen a video yesterday with a 64', 1,300 HP Comet, missing everything you mention here. $204,000 and 23 years invested and only a lap belt. First time out he rear ended a SUV at a red light, due to brake failure. Both occupants were severely injured. Had they had a harness they would of been fine injury-wise, financially, no.
 
Swinger 340 said:
Just seen a video yesterday with a 64', 1,300 HP Comet, missing everything you mention here. $204,000 and 23 years invested and only a lap belt. First time out he rear ended a SUV at a red light, due to brake failure. Both occupants were severely injured. Had they had a harness they would of been fine injury-wise, financially, no.
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It WAS a nice car, but if you're not gonna put a cage in a 1300hp car, why build it? To go for groceries and burgers at in-n-out?
There is a 40 Willys that I see here at shows occasionally. 10-71 blown 604" Arias hemi chevy...... with lap belts. Since no one will ever let him race it, why build 1600hp? Wouldn't 650 or 700 do just as well for a trip to walmart?
 
Swinger 340 said:
Just seen a video yesterday with a 64', 1,300 HP Comet, missing everything you mention here. $204,000 and 23 years invested and only a lap belt. First time out he rear ended a SUV at a red light, due to brake failure. Both occupants were severely injured. Had they had a harness they would of been fine injury-wise, financially, no.
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The car had harnesses in it, the Idiots weren't wearing them.
 
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