This is why you should have subframe connectors...

[Tunis]

... even if it is not factory correct.

Skip forward to 18:14. Notice how nothing on the car is sitting still? Doors, quarters, deck lid, everything shakes.

I don't remember if they put subframe connectors on it, but they did add some stiffening to the front end.

Edit: Just watched the first episode again and they did put a level 2 US Car tools stiffening kit on it. So what does one have to do to get the chassis even stiffer?

[Cuda70-74]

That's probably due to the body being so stiff all that vibration and flexing has to go thru something. I'm no structural engineer but remember the sheet metal on these's cars are not that thick.

[TobiasM]

Lots of things can be done in genreally to stiffen a car...strut brace front and rear, weld-in-cage, glueing sheetmetal, extra-spotwelds, glue-in rear/front window...just depends on how far you wanna take it.

Most common on Mopars for sure are subframe-connectors and torque-boxes.

I like that Fishtail-Cuda in that TV-show, but keep in mind that they also run tires with a very sticky tread and that are really wide...so getting these rear-tires spinning as at 18min14sec on the vid also causes much more stress to the cars body then getting to spin some stock 14" bias-ply tires with a width of a pizza-cutting wheel.   

[Tunis]

I really like it as well. I just thought that all that flexing in the quarters were an effect of a non-stiff chassis. I realize that putting super sticky tires on these cars will break something, unless care is taken. I didn't realize it was an effect of too stiff chassis.

[ViperMan]

I wonder if they used polyurethane bushings for motor/trans/diff mounts?  Those things are nearly as hard as plastic, so they transfer a lot of the vibration from moving parts into the chassis.

I'll bet some softer (but still good quality) mounts would reduce vibration into the body of the car.

[GoodysGotaCuda]

... even if it is not factory correct.

Skip forward to 18:14. Notice how nothing on the car is sitting still? Doors, quarters, deck lid, everything shakes.

I don't remember if they put subframe connectors on it, but they did add some stiffening to the front end.

Edit: Just watched the first episode again and they did put a level 2 US Car tools stiffening kit on it. So what does one have to do to get the chassis even stiffer?

It needs a cage, really.

I have a US car kit and can feel the doors bind when the car is on different height jack stands still. It's better, but it's not a BMW by any means.


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[Brads70]

They would need to add a full cage with front and rear hoops to take the flex out of it. With these cars the entire unibody acts like a big torsion bar. That's why I've said unless you add in torque boxes, subframe connectors etc.... adding heavy sway bars is pretty much wasting your time. The whole car is a torsion bar. Eliminating flex somewhere will just add it somewhere else and stuff will break , crack, fail. It just the nature of the beast.  Want to scare your self, jack up your car and notice how much it flexes before tires come off the ground.   
I can pretty much bet with great certainty that they will be constantly welding up broken mounts, floorboards etc.... on this car until they add in a full cage.
Those little tabs they made for the sway bar is not adequate in my opinion. It needs to be gusseted into the entire chassis . It will break there at some point. Same with the k-frame.....too lightweight
As mentioned tires make a big difference. 99% of us are used to BFG T/a's which are really poor tires from a performance perspective. 25 years ago they were cool but not now. One good thing about them is your less likely to break something else due to poor grip.  Biggest difference I noticed going to 315/30/18 up front was braking. Tires take much longer to lock up. At first I thought something was wrong with my brakes, but it was the wider sticky tires that changed braking performance.

[Tunis]

Cool, thanks for your input guys! I have so much to learn, but that's fun and getting input from people that know what they are talking about is great! I think that adding subframe connectors is the simplest way to keep the unibody from cracking in the roof-quarter seam without going all out cage. But I somehow expected it to be better with less flexing. So I'm I correct that go full cage that tie each corner of the car together is the only way to stiffen up the chassis enough so that it will not flex at all?

Per

[303 Mopar]

Cool, thanks for your input guys! I have so much to learn, but that's fun and getting input from people that know what they are talking about is great! I think that adding subframe connectors is the simplest way to keep the unibody from cracking in the roof-quarter seam without going all out cage. But I somehow expected it to be better with less flexing. So I'm I correct that go full cage that tie each corner of the car together is the only way to stiffen up the chassis enough so that it will not flex at all?

How are you going to use your car?  All out race, road course, drifting?  If you are just going to be street with maybe some strip time then subframe connectors are plenty, maybe add in a rad support.  I added subframes on all of my cars and it made a huge difference.

If you are all out race, then add a cage.  My point is a cage is overkill unless you really need it.

[61K T/A]

Maybe the flex in the front clip is because the k frame wasn't welded? I have a 6pt Wolfe cage in my other car. Definatly noticed better cornering now.

[HP_Cuda]

Funny how the front end shakes like it's a lift off fiberglass front end.

This thing definitely needs a cage for what they are doing, it's like going halfway on something.

[GoodysGotaCuda]

This thing definitely needs a cage for what they are doing, it's like going halfway on something.

I saw the car at SEMA and it was quite underwhelming...


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[Brads70]

I'd say unless you have a valuable collector E-Body then adding in subframe connectors is a great idea . I built my own and it literally cost maybe $20 in materials.

[Tunis]

I will use my car for normal street driving. I'm just afraid that I will torque-twist the poor thing without the subframe connectors. But I guess that is most unlikely unless it hooks really good, which it probably won't with street tires on a 15" rim.. I will add torque-boxes and I have started to fabricate some subframe connectors, just wanted to know if they add that much to the chassis before I weld them in. It has front and rear torque boxes. In either way, subframe connectors that are welded in place are not there forever. Heck, I replaced a few panels on my car, I think I can cut and grind them off if I wanted to, in the future.

Funny how the front end shakes like it's a lift off fiberglass front end.

This thing definitely needs a cage for what they are doing, it's like going halfway on something.

I know, the whole fender and hood area just rattles, same with the door. Makes me think that maybe they didn't have the most sound unibody to begin with. But what do I know, I'm still learning a lot. What about you guys dead hooking these cars without a cage on a drag strip. Does it shake like that in slow motion?

[Burdar]

The front fender is doing the most flexing in that clip. The factory put a brace from the center of the wheel opening, back to where the fender mounts to the inner fender. That brace was probably cut out for tire clearance. That's the main reason for that flex IMO. If that brace was still attached, the fender wouldn't move like that.