My date to bring the 78 Malibu to the fab shop is coming up. I stopped in today and discussed what needs to be done, and walked away even more confused than when I walked in the door. I'd like to build the chassis to run 9.xx, but will need to have it ready for 10.xx for the next couple of years. I believe it would be relatively easy to install the cage minus the front bars, which go from the front braces, through the firewall, and attach to the forward frame, at a later date. I'm not sure how to set up the back braces, however.

The fabricator suggested I run my back braces as far back on the frame as possible, and run another set of braces, the "X" brace from the main hoop to the suspension, tying in at the spring cups. In otherwords, I'd have two sets of brack braces, one to the rear frame, one to the rear spring cups. He suggested I run the back braces to the frame first, and if I wanted to, add the "X" brace to the spring cups at a later date.

I always thought the "X" simply tied in between the back braces, attaching at the top of one bar, and bottom of the other. I'd never considered attaching them to the main hoop, and spring cup. This is where the confusion comes in. I simply don't know what the best setup would be, and need a little steering in the right direction.

As always, your help is greatly appreciated! graemlins/thumbsup.gif

Hey Sean , I thought with a full frame car, which I think the 78 Malibu is, you only need a six point to run through the 10's. The nhra rule book is a pretty good resource. My 69 has the back bar going into the frame where the shocks mount through the package tray. the main hoop and forward bars are standard. You probably run at Southern Or. or Coos Bay, at Woodburn they look it over pretty good. I was told before I did it that with full frame cars they have to be welded to the frame. I'd verify everything before you get started. Also...Art Morrison and Alston catalogs have great pics and diagrams. Good luck, maybe we'll see you at Woodburn someday.

Hey Sean , I thought with a full frame car, which I think the 78 Malibu is, you only need a six point to run through the 10's. The nhra rule book is a pretty good resource. My 69 has the back bar going into the frame where the shocks mount through the package tray. the main hoop and forward bars are standard. You probably run at Southern Or. or Coos Bay, at Woodburn they look it over pretty good. I was told before I did it that with full frame cars they have to be welded to the frame. I'd verify everything before you get started. Also...Art Morrison and Alston catalogs have great pics and diagrams. Good luck, maybe we'll see you at Woodburn someday.

Actually, you only need a 5 point to 10.00 if the firewall and dash are un-modified. Note too, that a roll bar has to be 1.75" OD tubing but a cage can be 1.625" OD. If you are going to cage it, you could do it now and save a bit of weight. Chrome-moly will save quite a bit of weight over mild steel, too. An entire cage in CM (1.625" OD x .083" wall) will weight less that a MS (1.75" OD x 1.325" wall) roll bar. Particularly since you have to use 1.325"? wall for the MS bar instead of 1.20"? which should satisfy the 1.188" wall requirement. For some reason they will not accept 1.20" wall. CM requirement is .083" and is accepted at that thickness. If you just put the bar in now, the front halo will need to be 1.75" OD since the rules require that all parts are the same size, except the 1.25" cross bar behind the seat.

Thanks for the info, guys, but I was inquiring as to what would work best for back bracing.

Hey SS_ Sean, I have been helping a buddy install roll bars/roll cages here in north Georgia for the last 5 years +. We have done roll bars for several bracket race G-body cars & wagons. These have been stock suspension-roll bars. Lately we just finished a '78 Malibu with a chrome-moly cage/ladder bars/coil-overs for a heads-up class limited to a true 10.5" tire. This car will race 1/8 mile almost exclusively but if he runs 1/4 mile it could go a high 8 sec run. Anything below a 10 sec run will have to certify down to 7.50. For a bracket car/ 6-point roll bar which would be good down to 10 sec flat we use 1 3/4 mild steel tubing in .134 wall thickness instead of .120 wall thickness which most people use. Our reasoning is if the guy at the plant lets the wall thickness go a little below minimum requirements when being manufactured, then we pay the price if the car didn't certify when checked. We would have to cut out what didn't pass & do it again. I believe wall thickness in mild steel has to be no less than .118" wall thickness. This is why most builders use the .120 mild steel tubing. But mild steel tubing is manufactured with a looser tolerance than chrome moly tubing. Chrome moly tubing is bunches lighter/stronger and manufactured with a tighter tolerance in regards to wall thickness. But it is more expensive. As far as back braces, there are other ways to accomplish this task, but this is what we usually do. The two long braces attach to the top of the main hoop. If you keep the original trunk, the bottom of these same braces would attach to a 6" X 6" plate welded to the trunk floor as far back as you can get them. Then we would do an "X" brace as well. The top of the X would connect to the top of the main hoop but inside the two long back braces that run to the back of the trunk. The bottom of the X would attach to the same long back braces but much closer to the trunk. But as the builder you are using stated, the bottom of the X could also attach to the spring cups on the top of the frame. We would probably run a brace from the spring cup at the bottom up to the corner inside the main hoop where the bar that the seat harness attaches to attaches to the main hoop . This seat harness bar is horizontal when installed & runs from one side of the main hoop top the other. When a stock suspension Malibu launches, it is trying to push the car forward with the two bottom rear control arms. The two top rear control arms are trying to be pulled away from their front mounts. All of this happens because the rear end yoke is trying to rotate straight up as the car leaves and powers down the track. Be sure to have them reweld the stock front mounts for the top rear control arms and plate the outside of the holes for the bolts as well. The holes WILL elongate eventually if you don't and the mounts are trying to tear away from the car everytime you launch. Remember these are passenger cars & were built with Grandma riding around with her 267/305 powered street car in mind. Not exactly what we're trying to do. :D Remember, a triangle is extremely strong as it ties everything together & distributes the load equally. This triangle statement refers to the back braces/"X" brace combo/braces on top of spring cups. Sorry about all the long-winded rambling. Hope this helps. Dave H

I do not and would not run any braces back to the back of the trunk. They serve no pupose back there and only add weight. Your most important tie in points are the upper shock mounts, upper control arm mounts, and the lower control arm mounts.

I'm planning on re-doing my cage out of 4130 and this time will likely X-brace the rear shock mounts. You want to eliminate flex in the suspension mounts as that allows you to make small suspension changes and see results rather than your adjustments being wasted or masked due to flex.

There's nothing at the rear bumper that will help your 60' due to less flex, so why put tubing back there? If you drag the bumper on a high launch and it falls off, so what :D .

BTW, it's not legal to attach bars to 6x6 plates on a full frame car, plus it's not near as structurally sound as going right to the frame.

Hey Todd (10 sec Bu), Thank you for correcting me on the 6 X 6 plates on a full frame car not being legal. I reckon we've done too many cars with subframes (camaros, camaros, & more camaros it seems) than we've done cars with full frames. You definately hit the nail on the head with there being no need to extend the braces all the way to the back of the trunk. The rear mounting points of the frame only serve to keep the body off the tires and/or pavement. All of the forces the rear suspension sees is in the area of the control arm mounting points and then are distributed forward. Any frame structure behind the rear suspension mounting points only holds the body up. I believe I over elaborated on the point I initially meant to make. That point being that beyond the shape of the main hoop, to think in terms of triangles when it comes to braces & the rest of the roll bar/roll cage structure. As a X-brace is two opposing triangles, it is extremely strong in design. Hey SS_Sean, you would do well to listen to 10secBu as he has an awesome ride and has proven that he can build a G-body that flies ! 10secBU, you have an really neat car that I've been admiring & keeping tabs on for several years now. Hope your new motor combo brings the results you desire. My apologies to SS_Sean for the bad info earlier. On attaching the front down bars & main hoop, we've cut holes in the floor to access the frame. We then make a perch for the bars to be welded to. That perch is shaped like a V turned side ways and welded to the frame rail as the frame on a g-body is shaped like a C. Good luck with your project. Dave H

Running the main rear struts all the way back to the rear of the frame isnt needed to stiffen the suspension up .. but it does make a handy place to mount a fuel cell and battery(s).

Also .. if .120 wall was used instead of .134 wall tube/pipe wasnt the tube/pipe would likely get thinner than the .118 min. in the bends

when you guys are welding a C/M cage .. what handle/tip are you using to get the welds near the roof and other hard to reach areas?

On my car, it was built as a frame off from the beginning. All we did was unbolt the body and jack it up for easy access to all the roof & frame welds...actually not easy, but certainly better than not moving the body.

Some chassis shops will tack the roof line bars in and then weld the bottom of the windshield bar. The break the tacks loose and drop the two roof line bars loose and drop it down to weld the rest of the windshield bar.

The rear struts should be accessable as they come down on an angle away from the roof where they meet the main hoop.

On my car, I had the main hoop bent so it sat directly on top of the frame rails with no need to fab up any pads or mounts.

With the perches/access holes we use, you can cut the tacks loose where the cage connects to the frame/perches and shove the entire tacked together unit kinda over & down. Leave the perches attached to frame. Not easy or fun & usually some swearing involved. (usually only by me :rolleyes: ). This would only be the main hoop, A-pillar bars,and back braces. You can shove a piece of sheet aluminum scrap backed by cardboard between the area you are welding & the headliner/windows to keep from burning things up. All other braces/bars go in after the initial 6-point structure is reattached after all the top half of all joints are TIG welded. Kinda surprising how many cars we have seen in the past with big,nitrous motors and not welded on the very top of joints. Mostly though at the outlaw 1/8 mile tracks in this tri-state area. Hate to be in that car in trouble ! Tony, who is 6' 1" or so always manages to get everything TIG welded that needs to be. Might take a few minutes for him to get in & out of the car to do so. :D I've even run the foot control outside the car while he welds. Good luck & be safe. Dave H

Forgot to include that the top of the bar that runs horizontally from side to side in the vicinity of where the rear view mirror is also needs to be welded on top before the cage structure is permanently attached to the frame. Dave H