Say you have a 70 Chevelle with a 500hp-(flywheel) s/b motor, you want the car to handle said power, be able to take some turns when needed, and have a decent launch at the strip/street from time to time. How useful/beneficial would it be to box the frame rails and add tubular reinforcements being that this car will occasionally be raced but nothing too serious-a basic street brawler with no plans of exceeding a certain level of power. I'm aware of the benefits, but would it be overkill, hp robbing weight? Any thoughts would be appreciated.:)

never a bad idea to strengthen and stiffen the frame regardless of power level. Just make sure to add the bars where they help only in order to save weight. Some guys turn the under side of their cars into full on webs of steel with apparently no thought as to what they are attempting to accomplish. Is the car going to have a cage installed? If so the amount of bars installed under the car can be reduced quite a bit. If it were me I would try to tie the front and rear frame kick up together to make a double fraim rail and then run diagonal bars between the outside frame and the inner bar to triangulate them. A crossmember between the framerails just forward of the rear lower control arm brackets would also improve things and it would allow you a spot for a drive shaft loop. Without a cage torsional stiffness doesnt improve that much cause a flat plane is by far the weakest shape around. A box (a frame with a cage) is way way stiffer with even minimal bracing. Id consider the cage as long as it doesnt bother you. just my $.02

I would stop at boxing the frame as that will provide 80-90% of the benefit to be achieved. Adding extra tubes and such may look cool but does little for frame stiffness. Frankly most of the stiffness resides in the body not the frame.

boxing the stock open channel will add very little weight, but a considerable amount of stiffness comparatively.

I wish I would have boxed my frame before I had it powdercoated.
I also wish I would have installed a LS_ engine but maybe next time around.

You really need to determing the extent of racing you are planning on doing. Eventually you will come to point where the results from the modifications become minimal.

For example.... I want my car to handle decent.
I will be using the ScandC Stage II package up front with performance lowering springs and shocks. It won't be the best handling chevelle but it will do everything I want it to.
I could easily spend an additional $3,000 to make it handle better but my other car will still handle better than it.

Great feedback, thank you!

my gs is boxed from the factory

the big power buicks would twist a open chanel due to there big torque motors so all got boxed frames

so i think it is a good idea

Assuming Daves application but adding another 100-200 hp is frame boxing still the best option? should it be supplemented with a roll cage?

Thanks,
Sean

boxing frame and full cage tied in to front frame and rear will greatly reduce flex but with any hard launch or cornering it is going to flex some

cage will help but i dont see a major need for it

cage always helps. An 8 point cage will help tremendously but at the expense of room and that whole not being able to pull the body off the chassis anymore thing.

What about boxing the areas behind the rear cross-member? If I am going to box the frame, I might as well box the whole thing right?

What about boxing the areas behind the rear cross-member? If I am going to box the frame, I might as well box the whole thing right?


Just don't cover up where the bumper brackets bolt on.

What about boxing the areas behind the rear cross-member? If I am going to box the frame, I might as well box the whole thing right?


dont think it was a big issue there werent on the oem boxed frames

anything behind the rear wheels isnt worth spending any time on. You want the frame to be as stiff as possible between the front and rear wheels. Anything past that as no effect on the strength of the frame, unless of course you are hauling weightlifting plates in the trunk.

I boxed mine behind the rear cm. Basically for looks, and it was easy to do.