minitub frame notch bracing

[Iburyyou]

I am dse minitubbing my 68 firebird convertible and I was wondering if there would be a benefit to welding a piece of 12" long 1/8" steel to the opposite side of the notched framerail from the end of the top lip down to the bottom of the framerail. I inserted a picture to try to explain what I mean. Black is existing frame rail, red is new piece of metal I am thinking of. Any alternative ideas for strenth to a convertible.

[SatisTraction]

it cant really hurt except for weight and tank room but i do not think it is needed. if you wanted to brace it but not take up any more room then brace it on the inside of the frame rail. or use 1/4" plate instead of the 1/8" plate for the frame filler.

[Iburyyou]

my tank is out right now. does it sit that close to the frame?

[SatisTraction]

my tank is out right now. does it sit that close to the frame?

HMM, i do not know. i know you have to narrow the tank for the springs so you may be good to go.

[Iburyyou]

I'm putting in the 4 link so my tank will be stock size. I'll have to look into that.

[Modo Innovations]

I'm putting in the 4 link so my tank will be stock size.

I'm jealous...

I think that just the frame notch piece that you install will be strong enough. Especially, with such a large radius towards the back, plus your factory rear frame rails are just stamped thin sheet metal so with a 1/8" piece you should be fine. You have to remember too that alot of the convertibles strength in the rear is in the solid rear seat lean back brace, IMO.

[MrQuick]

You can just brace with 1/8" on both ends. On my most recent job I welded a section of 1/8" to the inside of the frame that remained then closed it off with 1/8" plate.

On a 4 link car there is alot less pressure on the rear section then that of a leaf sprung car due to the use of coil overs. Then you would have to strengthen the center section and cross member. If you are using the DSE kit then the supplied cross member is more than adequate. its a cool kit , have fun!

[Steve N 69 69 69]

I did that on my car, I put a piece of 1/8" along the bottom too, so its actually 1/8' box the whole area above the rear end. It may be overkill, but I wanted to be sure it was stiff and strong.
You can see some pictures here frame stiffener
I had heard that DSE was including templates like these with their kit now, but maybe not?! I got one of there first sets of deep tubs, back when the directions were on like 1 page of paper, so I kinda made it up as I went.

[Modo Innovations]

Steve,
I just looked at your site in your signature. I think I remember you posting about your wheels sometime ago. Are those Weld Wheels?
Man the car sure turned out nice.
Congrats.

[Jagarang]

Any alternative ideas for strenth to a convertible.

That last line is the quiet killer!

I think if your car is a convertible, you need to over brace EVERTHING. From what Frank(ProdigyCustoms) has mentioned about the vert he did, is that the car got really floppy when mini-tubbed. Be careful, take your time, and continue to ask questions!! It's not real obvious in your first post that your working on a vert, which is VASTLY diffenent than tubbing a coupe. I believe, you desperatly need a roll bar or cage to keep a vert straight after tubbing.

[Iburyyou]

I was wanting to stiffen the frame as much as I can because I would prefer not to have a roll bar. I am using the dse sfc's. I was looking for stiffening ideas for the car without using a rollbar. The car will have a strong engine but will never actually be roadraced.

[Jagarang]

In addition to future safety issues related to stress cracks in the frame etc secondary to a weaked structure, you have to remember that body flew will also affect your body work and gaps. Alot of work and money goes into getting a nice paint job with just the right fit and fitment. If the body flex degrades these things prematurely, your just hurting yourself in the long run.

I have a coupe and almost wish I had put a small cage/rollber in it just to help maintain and protect all the time and money I've put into the body work. Flew is brutal on bondo and paint, not to mention door gaps, windows, and seams.

I not saying you shouldn't do it, but just to make sure you do it right the first time so you don't need to worry about anything in the future.

If I'm nuts then perhaps someone can straighten(pun intended) me out.

I'm just trying to help a fellow car enthusiast make smart decisions.

[rob07002]

In talking with Frank at Prodigy its my understanding that a roll bar is HIGHLY advised. He also recommends extra bracing to the rear rails. I think he even mentioned running some braces to the rockers as well. I'm sure Frank will speak for himself and post shortly.....

[Iburyyou]

Other than the framerail being narrowed I don't really understand why minitubbing would affect the strenth of the body. The tubs are a little wider but still the same strenth of original ones plus the extra strenth of the dse crossmember. I guess my question is which part of this process is hurting the strenth of the car? Just the frame rail or the tubs or both? I am putting alot of time and money in this car and want it perfect when it's done. I appreciate all of the help I am getting.

[jeffandre]

I minitubbed my 71 Camaro (still have to weld the tubs in) and I notched the heck out of the frame to allow for a minimum of 1" tire/wheel clearance to the frame (using 19x13's with 345/30/19's). I added a piece of 'C' channel to the backside of the frame so that it appears to be a normal frame now. Then I built what I call a trunk subframe and welded it over the existing frame rails to help bolster the area. I will attach the roll cage to 2 points in the trunk, 1 at the subframe above the sway bar mounts and the other at the back of the rear frame rail.

I figured I was spending enough time on the minitub job that I might as well make sure the rear frame is as strong as I could make it. Better to be safe than sorry on this stuff.

[Damn True]

What about throwing something like this
between the rear frame rails just aft of your SFC's?

[Iburyyou]

Looks like a good thing to have. I'm not sure if that would replace a rollbar for stiffness which would be my goal.

[Damn True]

Well I sincerely doubt you can create the stiffness of a cage with anything but a cage. A brace like that one (Stielow used something similar in one of his cars) would be a huge step up in stiffness from merely installing SFCs.

[Iburyyou]

does someone make that part or do I make it myself?

[Steve N 69 69 69]

I think if you box up the frame, fully weld in the new tubs ( instead of the 40 or so spot welds the factory uses) and add the DSE crossmember, it should be stiffer/stronger than it was before, plus your using a 4 link, so the frame past the shocks is just holding up the gas tank.

I just looked at your site in your signature. I think I remember you posting about your wheels sometime ago. Are those Weld Wheels?
Man the car sure turned out nice.
Congrats

Thanks, I wish it was done ( not that I dont enjoy the build up) I had to take some time off for work, but I'm back at it full bore, I'll post some new pics soon.
yep they're weld Pro Star XP's , but if you want 18x12's your S.O.L. I just found out they stopped production after selling only 8 wheels, I got 2, so theres only 3 more sets out there. kinda cool exclusivity, unless I need a replacement