Body flex?

[85boostbox]

Anyone experience body flex? If so what did you do to remedy it. Specifically L body. But any other TM chassis is good. I know the roll cage stiffens everything up. But anyone go a step farther. Can be for drag or autox. I have some ideas in my head, but want to know what other people have done. Pictures would be great as well.

Paul

[thedon809]

I was wondering about this also. I have a front strut bar and want to add another bar near the rear struts.

[fixit]

sorry this might be a noob question..
how do you know the body is flexing ?

[going4speed]

L body is pretty stiff. Amazing how jacking up the front lifts off the back tire.

[GLHNSLHT2]

Lbody is pretty stiff. But stuff can be done. Big and fairly easy thing is to go to the j-yard and find 2 more Omni's, rip the headliner down, take the center brace from the roof, get 4 of the nut clips from the radiator fan on 2.2/2.5/3.0 Chryslers and then pull your headliner down and put the braces in the roof where the bean counters pulled the front and back one out and just left the center. You'll see the bosses for them, and the rad fan nut clips slide in and you can screw the braces right in using the stock bolts from the braces you got at the j-yard. This really makes an Lbody sound like Mercedes when you close the doors now. It also gives you 2 more spots to hold your headliner up.

For a rear brace You get some exhaust clamps, clamp them around the tops of the strut tower caps, weld 2 tabs on them and run a bar between them.

[knownenemy]

If the "L" body has issues with flexing,
I'm sure I'll find out about it directly.

In building my GLHS,
I set goals of 400FWHP, and 11sec 1/4 mile times, and a final weight of 2200lbs or less.
I think the two first goals will be surpassed greatly.
The last one is where I may find trouble. lol

My SWORN ENEMY is WEIGHT!
So much so that I'm going through the vehicle at the moment,
and removing any excess body seam sealer.
I have the entire car stripped down to a shell.
So, no time like the present.

If you get your interior this far apart, you'll notice that the assemblers
often wiped off the tips of their paste guns everywhere and anywhere.
Now this seam sealer may not be all that heavy in one particular place,
but I've removed a HUGE amount of it, and I'm nowhere near done yet.

Here's a couple pics:
Before


After(or during)


I'm not highjacking your thread.
I would be very interested to hear about anyone's experience with flex as well.

In the mid to late 90s, I had a GLHS that had nearly 400HP,
and the body didn't flex on it.
I POUNDED that car, and ran it for a while with the WG stuck closed!

[85boostbox]

No please hi jack away. Any and all info is appreciated. I know first hand that the front struts like to separate from the car. I will be already addressing that.

[thefitisgay]

I thought the best thing to stiffen a unibody was to weld all the panels together at the seams?

Besides a full cage of course

[going4speed]

Are those the most rust free floors of any L-body in the known universe? I think so!

[knownenemy]

No please hi jack away. Any and all info is appreciated. I know first hand that the front struts like to separate from the car. I will be already addressing that.

I hadn't heard of the struts "separating" from the car.
Do you mean the strut towers literally break away at the seams?

I would think this would be an issue I would have heard of previously.
It raises my interest, and gets my brain ticking in a way I don't like. lol
Now i'll have to go any double, triple check the towers,
as I intend to install relief "humps" in them to accommodate the 17" wheel/tire setup I'll run.
They don't rub right out of the box, but CAN rub over some intense bumps.
Or when the wheel is turned lock to lock, they can rub the transaxle,
or the inner fender.
(Just another mod that's best to do while the interior is completely removed)

[85boostbox]

Yes they separate from the seams.

[85boostbox]

One of my ideas is to take a 3x2 box steel and run it along the inner rockers underneath the seat supports. Like slide something in. And tie it from the front frame seam where the k member bolts to and the back where the back chassis bolts to.

[85boostbox]

I thought also of cross bracing the frames from underneath, but I don't think my 4" inch exhaust will fit.

[knownenemy]

Are those the most rust free floors of any L-body in the known universe? I think so!

Yeah, the car is a really clean specimen.
I bought it in 09 from Mike at FM.
He really got me a great car, and gave me a great deal.

It has only 67930 miles on it too.
It was pretty, but lacking in the performance area.
I just HAD TO make it a BEAST! lol

Thanks for the compliment.

[85boostbox]

sorry this might be a noob question..
how do you know the body is flexing ?

Doors not shutting right, looking at pictures of cars launching gives a good idea as well. Also body lines not lining up like they used to.

[dwh4784]

I wonder what they did to the convertibles to make them so stiff. When we had my Lebaron up on jack stands it might as well have been planking on the two front ones. All the weight in the front and still no twist or anything even when jacking it a corner at a time as high as the stands would go. The doors would still open and close. You could lift the back end up off the stands with one hand it was so light. Not sure this helps your question at all but it was definitely interesting.

[GLHNSLHT2]

Lbodys like to flex the front frame rails away from the inner fenders too. Stitch welding the seams there helps, though not easy to do with paint still on the car and all the drivetrain.


DWH, doesn't it have the big bolted on gusseting under the rockers? Shadows do, can't remember if your GTC did or not??

[knownenemy]

One of my ideas is to take a 3x2 box steel and run it along the inner rockers underneath the seat supports. Like slide something in. And tie it from the front frame seam where the k member bolts to and the back where the back chassis bolts to.

This would stiffen it up for sure, but the weight you'd be adding.....well, I guess I'm a bit nuts about weight. lol

I thought also of cross bracing the frames from underneath, but I don't think my 4" inch exhaust will fit.

The 4" exhaust really kinda prevents you from joining anything from one side to the other.

On another 4" exhaust note:
I've been considering designing a 4" cutout for my exhaust.
One that avoids the restriction most cutouts cause when they're closed.
I've been thinking of some kind of sleeve valve, rather than a fuel plate type(butterfly).

Lbodys like to flex the front frame rails away from the inner fenders too. Stitch welding the seams there helps, though not easy to do with paint still on the car and all the drivetrain.

This is great info GLHNSLHT2.
I'll definitely be checking into this.

I'm going to get one of those small MIG welders to close up a few firewall screw holes,
welding in my spare tire tub replacement panel, and welding the new cowl air inlet in.

I understand those welders are not really good for structure welding,
but what's your opinion on a few tacks on these frame rail/inner fender areas?
I guess a few beads couldn't hurt, no?

[ajakeski]

MIG welding is exactly the type of welding that should be used when working on these cars.

L body cars are stiff but suffered from poor welding from the day they were new. I remember working on Omni and Horizions back in the early 1990's that had strut towers falling apart because of too few spot welds and poor spot welds.

When I restore GLHS 420 I plan to add spot welds inbetween the original welds along the frame rails and strut towers. I'm also going to try to engineer a rear strut tower brace built into the floor and frame connectors.
I'll get a better idea of what can be done when it's on the rotissorie.

Another issue I see today is rusted reapir done poorly. Not just on our cars, but on most old car "restorations"

Case in point:

The floors of any car are stamped from large continuous sheets of steel. On unitized cars, the floor is a structural member of the car, tying the frame rails and body structure together.

I see floor and unitized body repairs all the time that consist of any random piece of metal tacked in place to cover a hole. Structural integrity is not restored this way and the unitized structure is no stronger than it was with the rust hole.

A repair done to any section of a unitized structure should be made with similar strength and gage steel. It should also be welded as a solid seam, not a few tac welds.

By unitized structure I mean any part of the bare shell of the car. Not doors, fenders or the hood.

Second point:

1/4 inch steel welded to the 22 gage structrue of a vehicle does nothing but add weight and create an injury hazard during a crash.

I've seen more times than I can count where someone welds a big thick chunk of angle iron to a unitized cars rusted sheet metal frame rail as a repair.

I can only assume this is based on the bigger is better theory. Not in this case. All this is is a missle waiting to launch from the car in a crash.

[ajakeski]

I wonder what they did to the convertibles to make them so stiff. When we had my Lebaron up on jack stands it might as well have been planking on the two front ones. All the weight in the front and still no twist or anything even when jacking it a corner at a time as high as the stands would go. The doors would still open and close. You could lift the back end up off the stands with one hand it was so light. Not sure this helps your question at all but it was definitely interesting.

LeBaron convertibles had chrome moly tubing running inside the rocker panels. This tubing was tied to supports at the front of the rocker and to the steel bracing that ran across the rear seat area.