VincentT

I feel like I've done my due diligence in researching this issue, but haven't found enough information to convince me one way or another. This coming summer I'm planning on dropping a 376/480 into my '04. I have everything figured out save for the exhaust, and my problem is pretty much an opinion/preference issue.

I'll preface it by saying that I still want the car to be as family oriented as it is now, but with a little more oomph. I still want to chauffeur my newborn daughter around, but I also want to be able to occasionally embarrass the occasional SRT Charger or 5.0 Mustang. As such, I don't plan on turning up the volume. Some Dynomax Super Turbos will help out back, but the exhaust manifolds have me debating which way to go. With compromise in mind, should I keep the current manifolds or go with some LTs?

On the one hand, you have keeping the current manifolds. I'm pretty certain they will bolt up to the new engine(if not, feel free to correct me). If that is true, this is certainly the easiest, but doing so essentially resigns me to the current exhaust setup, which is 2.5". This would keep things tame, but how much would it restrict the engine? And I'm not talking about, "You'll make more power with headers and 3 inch pipes." That's obvious. I'm wondering how much the manifolds will handicap (so to speak) the engine, if at all.

On the other hand, I could put in some LTs. This would certainly help the engine exhale, but would make things a little more noisy. I would probably coat the headers inside and out, and possibly wrap them on top of that, but to be honest I don't know how much that will help quiet things.

So, quiet but possibly restrictive manifolds, or good flowing but possibly louder LTs? No wrong answers here.

itsslow98

iTrader: (18)

Long tubes, high flow cats, stock resonator and stock or aftermarket catback will be pretty tame. Just dont do Corsa. Borla, magnaflow or stainless works will all be pretty tame.

minytrker

iTrader: (13)

I have a LS3 and am running OBX headers with cats connected to the stock exhaust. I also changed out the mid muffler to a magnaflow X pipe and the stock mufflers have been gutted out. Its actually pretty quiet (my G8 is alot louder) and it made the same hp/tq with the cutouts open and closed. Going 80mph you cant hear the exhaust in the car at all.

itsslow98

iTrader: (18)

Just for reference in case you guys werent aware....inside the factory resonator is an x-pipe.

DMM

L/T's connected to the stock exhaust is just right IMO. Quiet with a little rasp to it.

VincentT

Ok. Thanks for the advice, folks. I will ask a follow up question: How restrictive are the stock manifolds? Especially for a cammed engine that is a half liter bigger than stock. I will do LTs eventually I'm sure, but how soon depends upon that.

odthetruth

iTrader: (4)

Very.

StretchASU

x2...You will see noticeable gains from longtubes and a tune. The factory exhaust system flows surprisingly well. If you are doing a cam, you are kind of shooting yourself in the foot to keep the stock manifolds on there.

I am currently running stock manifolds, resonator and Dynomax Bullet Mufflers welded in place of the stock dumpsters. Its a nice deep tone but the sound disappears after 60mph. Just driving through town you can tell its not a base CTS but isn't obnoxious when I pull up to the office either. At the time I was concerned with the interference of the headers with a takeoff oil cooler adapter so I passed on LT's. If I had to do it again I'd just do the LT's and leave the stock catback since I am DD'ing the car more.

In a slightly different application I have a friend running 1-3/4 Pacesetters on his LS6 Goat and when he got it tuned post cam install was running it to the stock catback as well. He installed a some Spintech mufflers/catback recently and saw no difference on the dyno.
Vid of his original dyno pull.

minytrker

iTrader: (13)

I took my stock resonator and replaced it with just a x pipe on my G8 and it was good for 7 or 8 rwhp over stock so I figured it couldnt hurt on my ctsv.