according to NHRA rules the diagonal bars running off the main hoop need to tie into the subframe for going 9.99 and faster. Now the main hoop is going to come down right on the subframe, so how exactly am i supposed to pull this off. I was going to run the bars diagonaly below the rear crossbar to the tranny tunnel, but i doubt that the sheetmetal there would do much in a impact. Anyone have any ideas besides running a 2x2 bar from the rear sub frame to the front and welding the bars directly to that. BTW its a 14 point and i am making it a 1-off custom.

 

My subframe connectors run directly under my seat. There's no way I can weld to it. All my tubes are welded to the 6x6" plates that are welded to the sheetmetal. Each plate is heated up and bent to form around the sheep metal.

The main tube is welded to the hump behind the front seats. The main hoop braces are welded beside the tranny tunnel on that same hump. The A-piller bars, normally just the door bars, are welded just forward of the door opening. The rear bars are welded to the floor roughly above where the fuel tank would be.

Since all the bars are welded to the 6x6" plates, it passes a tech inspection but I've never had to get a chassis certification yet. I doubt they would fail it because of how I welded everything up.

Under normal installation even in a full frame car, the main hoop is supposed to be welded to the frame. To do this, you cut a hole in the floor, weld the tube to the frame then weld the floor section back in.

 

So you dont know if the main hoop braces will pass chassis cert? i wonder that if since i am doing a full 14 point if they would overlook the braces? i just dont want to run into any problems if i reach the 9's

 

Read the rulebook.

"All vehicles with OEM frame must have rollbar welded or bolted to frame. Installation of frame connectors on unibody cars does not consitutute a frame , therefore it is not necessary to have the rollbar attached to the frame"

"Unibody cars with stock floor and firewall may attach rollbar with 6" x 6" x 1/8" on top and bottom of floor (not possible on a third gen) or weld main hoop to sill area with plates welded completely around."

I don't see any problems in having my car pass a chassis certification. Under NHRA rules, if I go to an NHRA track, it would need one. I run under IHRA rules and don't need a chassis certification until I run quicker than 9.0 in the 1/4. IHRA rules are much softer in many areas. Even running in the 9's I only need a single layer fire jacket. Although I have a 2 layer jacket and pants, neck collar and gloves, I don't need to wear them under IHRA rules because I'm not fast enough for them to be manditory.

If you build a car that runs 9's or quicker, build it to pass NHRA and IHRA tech and you'll never have any problems. There's slight variations in both so get both rulebooks. Little things like IHRA requires cars running quicker than 11.49 to have a properly secured fire extinguisher in the car while NHRA doesn't care.

 

mine passed tech and i don't have the bars you are talking about.certified to 8.50.

 

I may be wrong, but I think you need to have cage Tig welded for 9's.

 

you only need the cage tiged if it 4130

 

As long as this "subframe" you speak of is at least made out of 1 5/8"x.118" MS or .083" CM (round tubing), or 2"x2"x.058" MS or CM (square tubing), the diagonal supports for the main hoop are not required. These are only necessary when the main hoop is welded to 6"x6"x.125" floor plates. My main hoop is attached directly to 2"x3"x.083" rectangular tubing that goes between my rocker panels and subframe (certified to 8.50). I do have the diagonal hoop braces though. I also see a possible discrepency in the rule book with what Stephen said regarding subframe connectors though. Find out who you local divisional chassis inspector is and give him a call, just to be certain.

 

Question fellas, some of you have seen my run

https://www.thirdgen.org/techbb2/sho...97#post2574797

some of you not. However im in the market for a cage which most likely will be getting the 10 point moly one from spohn and just puttin in the 8 point and just keepin the rest in the garage till i need it so i dont have to pay extra for a 8-10 point conversion. Anyways enough jabbering, i also do not have subframe connectors which i was looking into. So now my question is this. If i get the cage would i even notice if i didnt have sfcs in or is the mod really still worth it. Moneys tight and if a cage will do a good enough job holdin her together ill skip the SFCs all together. Thanks yawll.

 

I have both,
But think you are plenty fine with just cage - but if you plan to start dumping the clutch soon you could benifit from both..
I was in same boat as you, run car all last year no cage or subframes 10.90s. This year with cage and subs 10.89.
Hope for 70s in some good maryland air when I have time for a roadtrip.
Make sure you get a molly, got mine from competition eng. and the door bars w/swingout work with door panels.

 

You should have a cage/roll bar and SFC. Since the bars attach to plates that are welded to the floor, the front and rear sub frames, if you want to call them that on a third gen, are still only joined together with the multiple layer of sheet metal of the car. SFC tie the front and rear of the car together stronger than just a cage/roll bar will do.

A cage/bar will add some strength to the car but it's main purpose is to protect you in case of a crash. Unless you have a tube chassis car, the cage/bar isn't good enough to stiffen the chassis of a unibody car like SFC will.

 

k thanks