I've got a 4-point rollbar from jegs that I'm going to install once I'm confident with my welding abilities. I've been looking at the car thinking about where to attach the bars. The obvious point for the main hoop is directly over the LCA mounting point. The other bars would go as close to the shock mounting points as possible. Since neither of those two areas are totaly flat, what do I do with the spreader plates? Do I have to try to heat and contour those to the car? Also, on the passenger's side there is a peice of thin sheet steel tacked on nearly over the shock mount. It seems to be there just to make the 'trunk' area over the gas tank flat. Should I just cut that out and weld the plates onto the metal underneath?

The other question I came up with is; Since I'm not using the stock seat-belt mounts anymore(moving to a harness) would it be good to tie in the main hoop to the hard-point for the seatbelt? It would seems like a simple thing to do, and I would think it's actualy stiffen the chassis up a little since it would triangulate the LCA and the shock mount points with the gseatbelt hardpoint , thereby putting the force comming up from the shocks into the top of the pillar where it'd o through the a-pillar to the front of the car.

For the record I don't need this to pass any particular rule-book. This is a driver that I'll probaly put on the strip once or twice a year and it probaly won't be faster than 12.5 if that.(It's a hardtop) I'd like to get into autocrossing, but the class I'd run in won't require a cage or anything. Thanks for reading,

 

Since you don't require a rollbar, install SFC first. Rollbar is for driver protection. It doesn't add to chassis stiffness as most people believe especially with only a 4 point bar.

The 6 x 6 x 1/8" plates that the roll bar needs to be welded to don't have to sit flat. You can heat and bend them to fit around stuff as long as you still have that 24" of weld all the way around attaching the plates to sheetmetal.

 

if your firewall is stock you can bolt in the bars.

plate under the car has well

plate inside/plate outside under.

 

That sounds good until you see how uneven any part of the floor where it should be attached is. Bolting it in with a plate on the top or bottom works well when you have a nice flat section of sheetmetal.

 

Well, I definately will go with SFCs in the near future. But for the moment I'm stuck on this rollbar installation. I needed to replace the stock-malfunctioning-seatbelts, so I went ahead and got the harness I knew I'd want in the future, and some new buckets. So I've got to get the rollbar done in order to drive the car safely. After this all gets sorted my next move is to re-do the rear suspension bits, and I'll probaly avail myself the chance to do the SFCs then, whenever the time becomes available to do all that. I guess for now I'll work on bending those plates to fit the floor.

What about attaching the hoop to the seatbelt mounting pads? Would that even be worth the time?

 

Rollbar tubes still need to be welded to the 6 x 6 plates. Since the roll bar will never pass a tech inspection to allow you to run quicker than 11.50 in the 1/4 mile, how you attach it doesn't really matter. If you intend to run quicker in the future, if it's not installed correctly now, you'll have to cut it out and install a new one later.

To go quicker than 11.50, a 4 point won't pass anyway. Minimum 5 point but everyone installs the passenger door bar to make it a 6 point. I don't know the specs of the rollbar that you purchased but the tubes need to be 1-3/4" OD. .120" wall thickness if DOM, .134" if ERW tubing. You can always make the door bars swingout for easier access on the street. I have no idea on the requirements for autocross racing.

 

I'm going to be attaching the bars to the spreader plates. I'm talking about the top of the main hoop where it goes past the stock seatbelt mounting point on the roof. Where the shoulder belt used to go up through the headliner. I'd build a bracket going from there to the top of the hoop. That would mean that I'd have 6 attachment points; the two over the LCAs, the two by the shock attachment points, and two on the roof. Then if I do get past 11.5 I can always add door bars and the two braces from the main hoop going down to the subframe.

Anyways, I workin' on bending those plates now. Not workin' today(for money at least) so I'll spend the rest of the day getting that perfect. I'm just wondering it the extra braces are worth the effort.

 

if you put subfame connecters in first, you could cut a hole through the floor & weld the cage right to the SFCs. then weld a patch or plate around the floor/bar. probably stronger than welding to the floor? just an idea. i like your seatbelt idea.

 

a bit more work. yes.. but fun to some.

same has shaping them for the inside
it's never been that hard. thats all im saying.
and i would down load the new NHRA Rule book
to clear a few things up.

the right info. is good to know. right from the Book. clears all the small things up.
things not coverd. in this type of Q & A

 

The diagonals to the LCA do not make it a legal 6 point. You need the main hoop (2), the 2 rear tubes from the top of the rear hoop to anywhere from the back of the rear seat area to the back of the car, and 2 door bars. Adding the diagonals changes a 6 point roll bar to an 8 point roll bar but does not make a 4 point into a legal 6 point.

 

I have been building race cars for over 20 years. First off a well fabricated roll bar, not cage can gain 1/2 second to an ET. I have proven that to many customers over the years. So give it the credit it deserves. Sub frame connectors only really work when used in conjunction with a Roll bar or cage.

Since you are not required to add forward bars for what you want to run just go for it. Make sure what you do can be upgraded in the future if you decide to run in a spec series. It will save you time and money.

If you are going to run in Drag make sure the tubes are .125" DOM not .120". It won't pass the ultra sound test. Min is .118" and mill spec is .003-.004" and any tube that doesn't meet requirement has to be replaced making the whole roll bar illegal.

Most kits use .134 and will be ERW sometimes DOM. They use heavier because of liabilty.

Since you have a uni-body chassis and if you want to drag race and a roll bar is required for your speed you will have to add the two tubes to SFC or if you do not have them you can run to the tunnel.

There are tons of pictures of Camaro's on the web with legal roll bars. You can even call the tech in your local division to verify what you want to do. Like I said before better to build to a spec than not.

 

They are heavier wall because the thickness tolerance of ERW can be +.004 to -.009. The heavier wall allows the minimum thickness to stay above the .118" requirement. The .120" DOM varies so little that it's very unlikely it will go below .118". It's also easier to find .120" DOM.

 

.120 won't pass either. Need .125". DOM mill spec is between .002-.004 depending on Mill and Countries. I have replace quite a few mistakes over the years from people using .120 and .125" ERW. Mu Division Tech always asked me up front before he comes over the do Chassis Certs about what I used. Play it safe and use .125"

 

http://sphotos.xx.fbcdn.net/hphotos-...20918709_n.jpg

Well, that's what I ended up with. I hope ya'll can see that picture. What I did was take some 1-1/2'' .250 angle iron, and cut one to fit up to the shoulder-belt attachment pad and then welded another peice to the main hoop. I stitched the whole thing to the sheetmetal and cut all those little holes just to make it look cool. I'm not realy sure if it's doing much of anything useful, but the 'bar is 98% showbar anyways. Next project is the SFC's...

EDIT: I am aware that this setup is not a legal rollcage, as it lacks door bars. I put the bars in because it is inadvisable to have a harness without overhead protection.

 

I wish I had pics of my cage in my 85, sold the car years ago. I made similar plates, the cage was welded in but then I made 1/4 inch thick tabs and plates that bolted into the factory upper seatbelt mounts on roof/interior