I know about the torque boxes, basic subframe connectors, etc. Wondering if it is worth bracing from the outside of the cowl forward to the inner fender on a 68 B-body. Looking to keep mods as "invisible" as possible...

Thanks!

yes my challenger has that from the factory. any brace you can think of is most likely a good idea on any mopar

Well IMO smart engineering normally suggests one concentrate on the "weakest" areas first that give the most bang for buck. "Worth" will be your own personal calculation. Not sure what your goals are other then "invisible", nor what else has been done or is in the planning to help decide if your cowl brace achieves much. Anything you add will likely show an increase in chassis stiffness, but is it smart or needed? Based only on what has been shared to this point, I'm skeptical.

Simplest trick to increase strength and remain the most invisible is to simply increase any member thickness, however the obvious weight penalty its not IMO the best bang for buck because if that.

jcc- I'll try to give a bit more background/rundown...

68 Charger. 5.7 Hemi/A833 4-speed. SPC UCAs, boxed lowers, QA1 strut rods. Hotchkis rear leafs. I'm not going full Pro-touring, but I am trying to build a daily driver that handles as much like a new-ish car as possible without giving up too much of the classic look as possible. I understand that there will likely be compromises.

Currently, the car is disassembled and basically bare metal, so it's a good time to add some stiffening where it can do the most good.

Hope that makes sense, and helps guide any advice...

I would love to be in the situation you are in to have a car be disassembled and bare metal!
I would put that thing on a rotissere and get the welder out.

Stitch welding for the win!

I would hope then that SFC would be first task, and welded not bolted, use the largest cross sectional tube you can fit/accept, with that member's thickness is then much less crucial (using the contoured style means the smallest cross sectional area of that member, starts to control the installed stiffness), I am an not a believer in SFC AND torque boxes, kinda redundant, with torque boxes more of a band aid solution, if your welding chops are decent, welding every spot welded seam solid, would be a plus, but the weld joints are often dirty, thin, and out of position, but usually not too visible. A monte carlo style bar or similar, would be effective, but hard to position, and real in your face. I think stiffening your K member might be another best place to start, and is out of view, it is the foundation on a mopar's front end, most of the rest of the surrounding sheet metal mainly tries to keep it positioned, and stiff.

One thing worth adding to your list is full weld and gusset the K. I would do that before adding the cowl braces.

As a guess, the cowl braces will stiffen the sheetmetal somewhat though not add much to rigidity or strength to suspension mount points.

Cowl braces were added to reduce cowl shake, of the fenders flapping, not to stiffen anything chassis wise.

I might add, "and to make a powerful sales video"

On ANY "unibody" type car every part that is welded together that makes up the body IS the chassis. welding all the seams is a good place to start. as I said before any thing that can be done to tighten up the body is good on any mopar. I saw one company made a tube brace for the lower part of the rad support. welded on that would tie the two front frame rails together at the front. I hate to say it but the cars we all love are very flimsy. you think your charger is loose? try a convertible.

Apparently you do not know that the factory cowl braces are bolted on and about a sturdy as a pair of EMT conduit pieces flattened at the ends.

It is NOT a chassis item. Not even close. The aftermarket make have sturdier stuff, but not the musclecar era factory stuff.

Thanks guys. That REALLY helps!

I've done exactly what your trying to achieve, stiffening the body as much as possible without resorting to a cage. I stitched welded the entire underside of the car, torque boxes, lower rad brace, inner fender braces, subframe connectors, and even added braces underneath to tie the torsion bar member to the frame rails. I have even read some guys added a brace in the rear to tie the rear frame rails together. Some have even beefed up the rear brace the shocks mount to on the car. I've also beefed up and stiched welded and gusseted the k member, and added LCA braces.

I installed the entire XVMotorsports (now defunct but operating under one of the employees) B Body stiffening system on my 70 GTX. I also used an Alterktion and a 4 ling but, that car handles like a go cart. I had it on the Willow Springs 2 1/2 mile road course and it was a blast. DO IT!!!!!