Hellwig FX Frame Kit installation experience?

My problem with the boxed frame kits-

What does it do for you? Or what are you trying to get out of the car?

I could see the purpose if you are autocrossing the car and want a more rigid frame, but if you aren't running 200 treadware 275+ cross section tires with good control arms and an agressive alignment and driver that's trained, I am skeptical of the frame being the weak point
I can understand if you are doing a lowrider where you will be driving the car on 3 wheels
It's kinda worthless on a drag car because a good 10.0 cage will do more for chassis rigidity and you can actually get it certified and run faster than an 11.50


I just don't see a use case where boxing the frame gets you anything. It probably stiffens the frame but if you aren't aggressively turning corners where a second or two around the track pays off or trying to go on 3 wheels I don't understand why you would use it vs. just putting in a 6 point cage???

Welding in temporary braces induces more stress causing the frame to move which is what you are trying to prevent, its chasing your tail. Welding always causes shrinkage, you can't prevent it, only control it. Therefore you want to limit the amount of welding to as little as possible to limit the stress you are inducing into the frame. This is why the fractory often uses stich welds instead of full welds. Aftermarket companies have nowhere near the R&D budgets of the OEMs, so you need to take their word with a grain of salt.


The frame is assembled when its bolted to the body. Unbolted from the body the frame is even more of a wet noodle. To box a frame it first must be set flat, level, and square and then restrained to keep it that way. Next it should be checked for prexisting distortions. You can set the frame flat with jackstands with screwjacks and shims but they will do nothing to keep it restrained flat, the least little jostle will throw off the alignment which is why a jig is required for boxing.


You always need a jig for major frame welding and boxing is major welding. Lots of hotrodders have bowed their mid rails outward from botched DIY boxing. If the frame does shift, how would you know without the reference of a jig? If you box the frame into a twist or bend, it will be much harder to pull straight and square again. Its likec ngine machining, its best left to a professional shop, its not a shade tree or driveway job. Besides the jig you need a good welder with fine heat controls along with careful backstep welding to avoid limit warping. Once the boxing is complete, the frame needs to be checked again for any warpage and rack pulled if required.

81cutlass said:

My problem with the boxed frame kits-

What does it do for you? Or what are you trying to get out of the car?

I could see the purpose if you are autocrossing the car and want a more rigid frame, but if you aren't running 200 treadware 275+ cross section tires with good control arms and an agressive alignment and driver that's trained, I am skeptical of the frame being the weak point
I can understand if you are doing a lowrider where you will be driving the car on 3 wheels
It's kinda worthless on a drag car because a good 10.0 cage will do more for chassis rigidity and you can actually get it certified and run faster than an 11.50


I just don't see a use case where boxing the frame gets you anything. It probably stiffens the frame but if you aren't aggressively turning corners where a second or two around the track pays off or trying to go on 3 wheels I don't understand why you would use it vs. just putting in a 6 point cage???

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Boxing the mid rails reduces tornsional twisting, of the frame as C channels twist really bad. The best way to box them would be to stich weld additional C channels to form a wider box. Increasing the cross section area of a beam also reduces twisting. This is the method OEMs used to use to reinforce convertible frames. Cages while ok for racetracks are unsafe and even sometimes illegal for public streets. You really don't want a cage for a street driven car.

Street or track, a 6pt cage w/o a helmet is dangerous.

the helwig kit isn't just a box....at least not for the abody chevelles. The convertibles and the el caminos had different frames than the coupes from the factory and the kit is like that. more like a trapezoid. It also adds another body mount by the door. I think, on one of the videos on youtube, a guy stands on the frame and you can see the twisting and flexing......but not after the kit is installed. of course if you had a jig, use one, and of course put a tape on it. and it probably isn't on spec after 40 plus years. I am going to trust helwig's instructions and all the others that have done it. to each his own

WyoGN said:

the helwig kit isn't just a box....at least not for the abody chevelles. The convertibles and the el caminos had different frames than the coupes from the factory and the kit is like that. more like a trapezoid. It also adds another body mount by the door. I think, on one of the videos on youtube, a guy stands on the frame and you can see the twisting and flexing......but not after the kit is installed. of course if you had a jig, use one, and of course put a tape on it. and it probably isn't on spec after 40 plus years. I am going to trust helwig's instructions and all the others that have done it. to each his own

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As I mentioned before I did this to my 87 442.
I was impressed with the before and after. A cage isn’t practical for a cruiser. Strip sure.. The g body frames were flimsy with a lot of twisting… add something with more horsepower and you add more twist, thus why the gn had a chain to limit the engine twisting.
This isn’t rocket science ( no pun intended) and several points although true are a bit excessive as to the amount of distortion that will be encountered and as mentioned in the instructions you can’t stay in one spot long just like welding body panels is tedious because you tack and move . Yes there is shrinkage when you heat metal but you must pay attention to the process. I was constantly checking and measuring based on the factory manual and marks I made before I started.
All in all my opinion is it has value if your beefing up the hp. Just my humble opinion. And I do respect the knowledge and experience of others that have added to the conversation

scoti said:

Street or track, a 6pt cage w/o a helmet is dangerous.

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Agreed. I'd want to box my rails over having a cage in a car that I regularly drive on the street. Cages provide a lot, including something to smack your melon on- I couldn't have passengers.

Both frame modification options come with caveats.

Sweet_Johnny said:

Agreed. I'd want to box my rails over having a cage in a car that I regularly drive on the street. Cages provide a lot, including something to smack your melon on- I couldn't have passengers.

Both frame modification options come with caveats.

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There is a third option….

Last posts on that page and the first couple on the next page. This is what I’ll be attempting since I’ve got no place to take the body off.

UC645 said:

There is a third option….

1980 Pontiac LeMans Station Wagon - G-T-faux (stuck with it, and can't shake it... like a bad case of herpes)

Well the S60 was ordered with 3.73s and LS1 housing ends (for LS1 brakes) in a stock width - we got an amazing deal. So the 8.5" and 7.625" are up for sale. In other news we are LS-ready! 10" x 2" oil pan notch is done with two 1" x 1" x 1/8" square tubes stacked; and the A/C compressor notch...

gbodyforum.com

Last posts on that page and the first couple on the next page. This is what I’ll be attempting since I’ve got no place to take the body off.

Click to expand...

Interesting. It seems that a few people have considered it but only one has actually done it, and it appears to have worked to some degree.

I'm just a skeptic that boxing the frame does much for you. Is the stock unboxed frame flexible? Sure, but what does make it stiffer do for you? Handling? Better ride? I just don't see a strong case to box it besides 'I'm making it better'. What's the problem with the existing frame and why are you trying to make it better?

I'm not a huge fan of taking the frame without the body on it and showing how it bends. It's like the classic shoe box without a lid problem. Of course the frame (bottom of the shoe box) is flexible, you don't have the body (the lid) on top. I see boxing the frame like laying another sheet of cardboard in the bottom of the bottom half of the shoe box. It helps, sure, but not much.

Can a cage be dangerous without a helmet? Sure, but it depends what you want to do for the car. My turd runs low 11's and I don't have a cage because I agree, a cage makes getting into the back seat harder and I don't want to cut the thing up to fit a jungle gym. I also autocross the car and street drive it a lot, but I haven't experienced a use case where I have thought that boxing the frame would benefit anything.

I did weld in some trick chassis UCA and LCA rear bracing because on hard launches I could see the rear end oscillating forward and back in the chassis on slow-motion launches.

I'm sure the car twists a bit on turns when I am aggressively autocrossing it, but the car can outperform my driving skills without any boxed frame so again, just don't see the point.


I'm not saying boxing the frame is wrong, I just haven't experienced a case where it would make my 550hp high 10 second capable, drive on power tour, autocross capable setup better.