GM A-body Convertible Frame Stiffening kit?

[GoldHawg]

I've seen a number of vendors that offer frame stiffening kits, some that say they are much stiffer than just boxing the frame like the convertible has. Does anybody make a kit or offer partial kits for a convertible a-body chassis to stiffen a convertible? Anybody done their own w/o a kit? Love to see some options for my 71 Cutlass Droptop.185378

[Hotwire]

Seen some people using this but can't comment on it as I don't have any hands on experience: https://www.summitracing.com/parts/sum-770800

[GoldHawg]

Interesting. If you go to that kit (which I thought was for hard tops only) in the questions Summit said in 2019 that it wouldn't work for convertibles, and just recently they said yes, with trimming. I've sent multiple emails into HPI (the manufacturer) to ask if it could work, and I've not been able to get them to respond.
Will this kit fit 1971 Chevelle "Convertible". Apparently Hellwig kit will not. Thank you.
Asked by BENTON on January 26, 2021

A:
Thank you for your question. The Summit 770800 frame brace kit will work with a convertible or factory boxed frame with trimming.

Summit RacingSummit Racing Answer - January 27, 2021
Q:
Does this kit fit 68-72 A-body convertibles? The frame is already boxed, but this kit includes the box kit and frame braces...just wondering if the bearing will fit convertible frames, as they are different from the hard tops.
Asked by ANTHONY on August 13, 2019

A:
Thank you for your question. The Summit 770800 frame brace kit includes parts to box the frame, and as you stated yours is already boxed. It also includes bushings that are the wrong size for a convertible. At this time we do not offer this kit available in pieces or specifically for the convertible.

Summit RacingSummit Racing Answer - August 14, 2019

[Mr Nick]

My general assumption is you would not use the "boxing" portion of the kit, since the factory frame is already boxed. And the trimming they are referring to would be to shorten the areas I circled in blue, since they would mount to the factory boxed frame (which is boxed at an angle) and not to the verticle pieces included in the kit.

So, I think an experience shop could make it work. What is your goal by installing a boxing kit? Improved handling, less body twist/cowl shake, just curious as it may not really do much depending on the results you're expecting.185400

[raustinss]

follow Nicks advice ,everything should work out fine lol As for HPI ... dont get me started ,they redesigned their frame brace kits around my ideas and are brutal to deal with . if you get an HPI kit get it thru summit and only thru summit . cheers and good luck

[GoldHawg]

Thanks..helpful. The (in)experienced shop that installs would be me. I can cut and weld, but I don't have tubing benders and my time is worth a lot to me, so I'm ok buying the kit. My goal with a stiffer frame is less chassis flex, hopefully better handling, and I'm thinking about putting a turbo on my 6.0 LS, so thought chassis stiffening would likely help.

[proper]

I used the Helwig on my 65gto chassis along with some other reinforcements and it’s a nice kit. Have you given any thought to getting a coupe frame and redo it. This way time is on your side and when it’s done just have the shop do the remove and replace all in one shot.I’m sure your stock convertible frame has good value and would sell easily but when you lift the body there’s going to be some surprises and as shop time goes ,time is money.Just my 2 cents

[GoldHawg]

I already have an alternative frame. Unfortunately it's already powdercoated but I'll just have to redo it. When I do the work (and it will be all me and perhaps some friends, I will be doing as you suggest--roll out and roll in.

[andrewb70]

Adding even a 6 point case would do more for chassis stiffness than any of those kits. A ladder is still a ladder, no matter how many rungs you add. In order to add stiffness, you need bracing in the 3rd dimension.

Andrew

[Hotwire]

To get better handling you need to ditch the front factory geometry, it's trash. The a-arm pivots are taller than the pivots @ the spindles, this creates a parallelogram that changes your camber as the suspension travels through it's compression. When the suspension compresses you get positive camber (top of tire pushes out) which is exactly opposite of what's needed.

I received a very clear message from UMI when I was running my stock suspension at a small autocross event. They took pics and shared them with me. I even had the front tires pushing out into the wheelwells scrubbing.

Suspension droop causes negative camber, works against the direction you're turning:

https://hosting.photobucket.com/albums/yy69/Hotwire454/Project%20Salty/.highres/Jeff%20Bowne%2023%20of%2040_resize_12_zpsbwm9irnu. jpg?width=450&height=278&fit=bounds&crop=fill

Suspension compression causes positive camber, works against the direction you're turning:

https://hosting.photobucket.com/albums/yy69/Hotwire454/Project%20Salty/.highres/Jeff%20Bowne%2029%20of%2040_resize_6_zpsgfqzkwra.j pg?width=450&height=278&fit=bounds&crop=fill

The lurching at 24-28 seconds is my front tire digging in to the wheel well, could smell burning rubber after the run: https://youtu.be/KojEWB45AUo

https://hosting.photobucket.com/albums/yy69/Hotwire454/Project%20Salty/1013191620_HDR_resize_8_zps4hlregvj.jpg?width=450&height=278&fit=bounds&crop=fill

[67-LS1]

Man, I so want to do this but I just got my car back on the road after having the body off. Is there any way to add frame boxing with the body in place?

[raustinss]

You cant 100 percent lol but you could .... remove all body mount hardware on one whole side of the car , loosen the other side and jack the body up , you might just get enough room to get it done . at that point id just say screw it thou and take it off the frame