Running without tunnel brace

[BullF-16]

Pics now included in post #17

UPDATE - ARH has called numerous times today and are working diligently to make sure the exhaust can be used with the brace! They are doing all this and dealing with the aftermath of Irene simultaneously....Thanks ARH


I recently installed ARH Lt headers and mated it to a SW retro 3" catback. I did not mate up to the SW systems without some minor fabrication. Anyway, the shop that did the headers said that the tunnel brace was not necessary and some Header/catback manufacturers even state that when running headers to a 3" exhaust that the tunnel brace could not be used without hitting. It runs perfectly and i notice no discernible difference from before.

I know it provides lateral support for the tunnel, and the fact that the shape of the tunnel due to physics really benefits from some form of support connecting the open ends of the tunnel together. But really how much is necessary. I know the driveshaft bearing is in this area but connected to the top or apex of the tunnel and i dont see how it helps here. I am not a street racer and can deal with some frame flex but again, i have not noticed any.

The problem is the x pipe hangs about an inch below the tunnel. I am going to put the car up on jackstands again and loosen everything up from the headers back and jack up the exhaust at the tunnel brace area and make other adjustments as required to try to get the xpipe up further in the tunnel.

I ordered an Elite Engineering brace with an additional 1/4 or so inch of clearance and can re use the dogbone spacers that came with the SW retro exhaust to further get clearance.

If this can not be done, what do you think of this. allow the exhaust to rest on the brace and i will fab up a mount or bracket to physically attach the pipes to the brace by welding a bracket to the pipes then running a bolt thru the bracket to the brace and tightening it down with a nut....no vibrations or knocks when going over rough surfaces.

I have read other threads about not needing to have the brace in place and i have also read that it is absolutely required.....

What is the real consensus as to the necessity of it and how many here are running without the brace, and it you have headers and a 3" exhaust, how did you get it to work.

Thanks

[honeybucket99]

I took the position that the brace was there for a reason and will not run without it. It is kind of like when I fly, I let the pilot do his job with no advice from me Maybe naive, but that is how I roll. Now, at least you had a choice, but I had Vengeance racing install my headers in the Spring of 2010, and only learned that they had deleted my brace when I installed my exhaust in Summer 2010. Needless to say I was pissed at having to spend $100 on something that should have been put back on the car by Vengeance.

[BullF-16]

Yea, if I was your pilot I would not take to kindly to your advice especially since in the jets i used to fly you would be sitting on my lap!

Anyway, i am gonna crawl under the car once my elite engineering brace comes in and see if i can make it work. If not, i have a shop in town that does custom exhaust full time and i will see what they say.

I also have an email into Chevrolet, and requested a response from engineering/design to get the real answer....we'll see, im not holding by breath. I know many of the header manufactures say to not use the brace if using the 3 in exhaust with header combo.

[SSE 4 2SS]

Hey Bull,

First and foremost, let me thank you for your past or continuing service to this country...

My dad and brother are both retired Air Force, my dad as a crew chief and then Chief Tech Inspector, and my brother as an NDI dude... We referred to it as "no duty involved."

on to your question..

This will sound strange and it may not be the case, but I've seen a few cases where the X pipe was installed upside down and this created clearance problems... I'm running three inch pipes and have no clearance problems...
Just a thought...

I know the tunnel brace looks flimsy, but it is there for a reason...

good luck with the search for information...

[GTAHVIT]

I used some washers to drop mine down... I think I have 3 3/8" washers on each bolt.

No problems hitting the tunnel brace any more.

[BullF-16]

I had the washer thing going when i did the install to the stock manifolds. not an issue. The headers are lower than the stock manifolds and the xpipe is a good inch below the tunnel brace. I havent put it on jackstands to check things out, looseness etc but plan on in when my new tunnel brace comes in. I am sure the shop that put in the headers knows better than putting in the x pipe wrong. I will look at that also.

[GTAHVIT]

You might be surprised how many X pipes get installed upside down..

I kinda like the idea of attaching the pipes to the brace...

[IROCanSS]

Goo look in the GM engineer thread. I posted why I have heard it's there. Side impact rigidity, keeps the trans tunnel from collapsing under hard lateral impact.

Yes, I am an engineer

No, I don't have a tunnel brace


DO NOT ATTACH THE PIPES TO THE BRACE!!!

The pipes need freedom to move or you will get one hell of a vibration! Make sure you have 1/4 to 1/2 between the brace and pipes.

[BullF-16]

Originally Posted by GTAHVIT

You might be surprised how many X pipes get installed upside down..

I kinda like the idea of attaching the pipes to the brace...

I really think this would work. Run a piece of 1/4 inch flat bar stock across the top of the exhaust with a hold drilled in it. run a long bolt thru it and thru the tunnel brace. Pop on a nut and cinch it down. Voila, no rattling, no issues. surely it is not that simple though.

[IROCanSS]

The exhaust was accidentally attached to the brace on our supercharged mustang... Sounded like the car was going to explode. A five minute adjustment to get 1/4" and all was good. Trust me, don't connect them! There is a reason why the exhaust hangers are rubber... It isn't for ease of install

[IROCanSS]

...especially if you have an aftermarket cam! Remember, the engine moves... A LOT. The headers are hard mounted to the block and the exhaust has all rigid connections. If you solid mount the exhaust to the tunnel brace, when the engines moves around it's either going to break something of make a horrid sound.


Now on topic... You're likely 100% safe without the brace. Not like the car is going to wrinkle like piece of paper without it if you get into am accident. Like I said, I don't have one. Guess I'm a rebel

[JDP Tech]

Yeah, idunno, the engine moves a lot while driving (unless you install some Pfadt engine mounts), and the exhaust moves even more, so hard bolting it to the chassis probably isnt a good idea, and could be very bad for your headers or heads, when the engine is torquing back and forth, and the exhaust is held in place. It would need some sort of flexible bushing or something.

If you do any spirited driving, I'd definitely have the tunnel brace in position.

[IROCanSS]

THANKS Jeremy.

I just called my shop that took my brace and I'm picking one up today!!! I'm doing a "flat out" road course day in a few weeks... Guess I should get it mounted.

Plus, all I do is spirited driving!!

[GTAHVIT]

Originally Posted by jrhaus76

The exhaust was accidentally attached to the brace on our supercharged mustang... Sounded like the car was going to explode. A five minute adjustment to get 1/4" and all was good. Trust me, don't connect them! There is a reason why the exhaust hangers are rubber... It isn't for ease of install

I certainly won't argue this...

When my exhaust was hitting the brace it was enough to trigger the knock sensor..