mdchaser

Hi folks, I have a 2011 GS manual with an A&A blower, cat delete, and a B&B fusion catback system. The car makes 560rwhp and is loud which is good. It is also unfortunately pretty raspy (happened when I swapped straight pipe in for the cats). I have two goals, the first is to make a bit more power of course and the second is to maintain or increase volume while losing the raspy sound. My thought is to purchase this:

http://www.ebay.com/itm/OBX-LT-Exhau...-/171061800237

I have a few questions:

• Will this work on a 2011 grand sport? It states it's for a z06 but my understanding is that it should work.
• Is a larger 3" system a good idea on my car since it has the blower or should I go with a smaller 2.5" system?
• I know I will need some sort of 3" to 2.5" converter to mate it up to the fusion system and maybe some o2 extensions but is there any other hardware that will be necessary?
• Is there a better place to buy this system?

I had a h/c c5 with an obx set of headers and really liked the sound, they are also a lot less expensive than other brands. Any other thoughts would be appreciated!

Thanks,

Jeff R.

Klarenbeek84

make sure to get your clutch/slave cylinder line moved out of the way. I just installed obx on my 05 this past weekend and burnt it in half and caught it on fire. It's a big job to replace the slave cylinder and I'm still working to see if I can just repair it. Some of the kits like Kooks come with something to hold it back so that doesn't happen.not sure if the kit you are looking at will fit though just thought I might try to save you some potential problems.

mdchaser

Great advice, thanks! I'll make sure it's safely out of the way so I don't destroy it with hot headers.

Dano523

With blower, you want 1-7/8" header pipes (not the 1-3/4").

X pipe is more for what is has to bolt up to, so 3" X pipe will work, but will need a reducers at the back of X pipe if your mufflers have 2-1/2" pipe on them.

As for high flow cats, get them instead of going cat'less, since the HP reduction will only be around 4hp with the cats (yes, they flow that well), and the car will not stink of unburnt full at every stop light.

As for with headers, different kind of sound (little louder at the muffler), and more sound at the engine bay, since the header have less sound dampening then the OEM manifolds.

As for the power you should pick up, at least 30+hp with the retune.
The reason for this is the exhaust scavenging that LT headers collectors achieves clearing out the old gases in the header pipes before the engine fires through them again .

mdchaser

Thanks, I figured I'd want the larger headers with a blower but wasn't sure... What do you think of the linked OBX system?

mdchaser

Killer video Dano!

Brandon619

I second that, that was a great video.

Dano523

Will fill the need nicely, since it comes with cats, and has 1-7/8 header pipes. Also, don't forget that you may need front 02 cable extensions.

Now the bad news, the bolting hardware/ band clamps, and gaskets that comes with the kit, throw them in the trash and replace the these parts with better quality parts instead.

So lets run through this.

Get the kit and send the headers in to be ceramic coated before you install the kit. The difference is engine bay temps will be night and day difference of the headers heat coated or not.

On the X pipe, since it sounds like you will need 3" to 2-1/2" reducers on them, have the back of the X pipes shorted and the reducers welded onto the pipes. Also, you should be rear O2 deleted already, make sure to plug the rear O2 ports in the X pipe.

Pick up a set of ARP header studs with bolts. When you go to install the headers on the motor, having the ARP studs installed makes it that much simpler, since you have the studs to hang the headers on heads before they are bolted down (and hold the gaskets in place as well).
Note, with the stock exhaust off, now is a good time to install the starter heat sheild, and make sure to get all the lines out of the way of the headers path so you don't melt them, even with the headers heat coated.

On the header gaskets, reuse your old OEMs (if they come off clean). If the OEM manifold don't come off clean, then pick up some OEM to replace them. Don't use the gaskets that come with the kit.

Now using better bolts and nuts, install the cats onto the header flanges. Using the clamps that come with the kit, lightly connect the X pipe to the back of the cats, the other section of the X pipe to itself, then lightly connect the back of the X pipe/reducer to the muffler pipes with the OEM clamps that came with the car.

Once you have everything dry fitted under the car, tack weld the back of the Cats to the front of the X pipe and the middle section of the X pipe to back section , pull the X pipe and do full welds of the cats to the front of the X pipe, the middle X pipe section instead of using band clamps. Hence fours less clamp seams, then just asking for a exhaust leaks with the band clamps there instead.
Note, you have to dry fit the X pipe to get it to the needed lengths to begin with, so don't just weld them together before dry fitting first in place under the car!!!!

With the cats to X pipe front and X pipe front to back welded, now you can bolt the X pipe back to the headers.

Now the fun time, and that is getting the muffler tips level as you bolt the back of X pipe/adapter to the muffler pipes.

The best trick, put a 2x4 under the Muffler tips, and use a jack to hold them level, without a lot of pressure on the tips to push the muffler up so they are not longer on the hangers. Short of that, second sent of hands to hold the tips in line instead as you bolt each band clamp one at a time. Also, Little heads up, but you may need to adjust the mufflers a few times over a few weeks; until the headers and X pipe metal takes a set from heat cycling.

As for what is left, more gas out due to the header collectors savaging, which means more air in, so time to re tune the car.


And yes, the OBX headers are a great produced clone of another type of headers, and give them a huge thumbs up. USA headers are no better, or worse, and all you are paying for is the increased labor and mark up costs from them being made in the states instead.

And before someone gets on a tangent about non USA parts on a USA car, the Vet is littered with import parts to begin with. So like the vet itself, it all boils down to USA labor putting the car together, and the same will be of the headers kit as well.

mdchaser

I have this strange urge to yell "bookem Dano" while throwing a set of cuffs over my shoulder... Strange.

That is a great post! I will definitely get them coated, I found a place locally that will ceramic coat them. Are you talking about these arp studs?


Can I get away without them? They are pretty damn expensive!

And finally where is the best place to purchase this kit? I live in CA so I'd like to find some place that doesn't charge tax/shipping, timing isn't particularly important. Amazon has what appears to be the same set but the primary diameter is 1.7" and I'm not sure if that translates into 1 7/8 or 1 3/8:


Thanks for the great info, I'm going to print it out for the install!

Dano523

The stock exhaust manifold bolts will work fine, but you will need a extra set of hands to hold the gaskets in place as they are installing the bolts to bolt the headers to the heads to begin with (your going to be under the car holding the headers up).

1-7/8" is 1.85", and 1-3/4 is 1.75".
So again, you want the 1-7/8"/1.85" tubed headers with the super charger in play. The smaller tube 1.75" headers are for N/A cars under 500hp, which helps them to produce a little more bottom end instead.


Also, Keep in mind that there is no CARB# for long tube headers nor the high flow headers as Ca legal after market parts to add legally to a CA licensed plate street driven car.

How you happened to get through CA Smog inspection for plates with a supercharger (some kits do have a Carb #) but no cats, your going to need to pull the same magic with the headers and high flow cats on the car for future smog inspections/plate renewals as well.

mdchaser

Thanks for the conversion, the amazon listing has the primaries as 1.7" but when I emailed they said it was 1 7/8... It looks like the same 1 7/8 kit from ebay so I may just order it and hope for the best!


About CARB... I don't exactly smog my car, I had the opportunity to register it in a county that doesn't do smog unless you sell it so I'm not terribly worried about it . The blower kit actually has a sticker so the only thing that would get me will be the headers if I do have to smog it!

schpenxel

You can buy a few cheapo studs from mcmaster carr or wherever to hang the headers/gaskets on during install. They are M8 x 1.25 if memory serves. Could probably use some threaded rod from Lowes or something if they have the right size. Just thread it into two bolt holes and then you can hang the gasket and header on those while getting the rest of the bolts started.

Def. no reason to spend $100+ on ARP header studs though. Stock ones will work just fine.

mdchaser

Good idea!

Another thought, I might as well replace the tunnel plate while I'm doing the work. Will I be able to use a 3/8" plate or will I be stuck with a 1/4" plate using these headers?

Thanks!

Dano523

Will have plenty of room for the 3/8" plate, and if you are going to re-plate, then heat shield the plate as well.

https://www.corvetteforum.com/forums...cs-review.html

mdchaser

What do you think about this one, it's cheaper than the elite engineering plate and has a ceramic coating rather than heat shielding:

http://www.thelapd.com/profile.asp?I...&CategoryID=32

Thanks for all the advice!

Dano523

Looks like a winner, plus no thermo blanket to get destroyed in the long term as well.

When you get it installed and a chance to see how much is stiffens up the frame, take some photo's and do a write up on it!!!!!

brewcitygymratt

Since I'm reading this on a smartphone I'm not sure if a clamp brand was mentioned yet(tiny fonts). If not, I highly recommend accuseal torco exhaust clamps for a leak free installation. Dano covered everything very well. I also have obx long tubes on my heads/cam/ported fast setup. I was in a hurry to mount them so I never had them coated. I have a Dewitt's rad+dual fans+manual fan switch setup and car rarely gets over 180 unless it's stupid hot out. The manual fan switch comes in handy at the dragstrip when you are waiting in line with the car off.

Dano523

The only band clamps that you want in play are the back of reducers to the muffler pipes,and here, use the OEM band clamps that are already on the car.

The joints after the cat to the front of the X pipe, and the middle section of the X pipes, you want to have these seams welded solid, after you have dry fitted the sections together for the needed distance, and spot tack welded the section before dropping the fitted X pipe with cats.


Also, not a bad idea once the pipes have taken a set and you have the mufflers tip adjusted correctly, do a small tack weld of the reducers to the muffler pipes as well.

This will keep the muffler pipes from rotating on the reducers (that are only held in place via the band clamps) to cause the muffler tips to be canted down the road. If the mufflers have to be removed, then tack welds are easy enough to grind off, and the X pipe will drop out from just removing the collector bolts from the header to the front of the cats.


Bluntly with all the extra band clamps/un-welded seams, trying to keep the muffler tips level, and not ending up with exhaust leaks in the lines at the band clamped seams, will be never ending nightmare.

mdchaser

Excellent idea, I'll look them up today!

mdchaser

Thanks for all the advice Dano, you are definitely an expert with this! Now I just need to get the funds together so I can get this done soon, don't want to have to wait for another driving season to come around.