The Alchemist

iTrader: (19)

So I am having Thompson Motorsports build me a new LS3 based motor, and I need to decide on headers. This isn't a max effort build, as I'm still using the D1SC, maybe an F1-A someday, but I want a car that is still somewhat quiet/livable on the street, so I'm going to keep a catback on the car, which right now is a Magnaflow.

I need to make some decisions on exhaust. I think a 1 7/8" header, with a 3" ypipe to a 3.5" new catback would be a nice combination, but now is the time to make decisions.

For reference, I made 760/706 with original QTP's (non-merge collectors) into an older style Kooks ypipe, then magnaflow catback, all with a NA cam which is one of the reasons the power tapered up top.



So now I'm going bigger cubes, better cam for a blower, still the D1SC (unless I find a deal on an F1-A) and need to make some decisions on exhaust.

So 1, 1 7/8" vs 2" header, will I really notice any difference between the two considering the cost difference? Second, catbacks, who makes a 3.5" catback that is still decent sound wise?

Thanks guys.

SCott5

iTrader: (40)

What about the kooks true dual setup?

02LS1ram

iTrader: (17)

Your exhaust system looks pretty stout. I think 2inch headers would be more of a waste of money then that big of a jump in power. Add and E-cutout. It's cheap and will pickup the extra power you want. Plus it's fun to make a lil noise and then quiet it up. Also what happen to the 347 you built ? That seemed like a nice lil power plant why the change.

conan

iTrader: (5)

What happened to your 347 you put together ? Just want more cubes ?

ramairetransam

iTrader: (18)

i have a 3.5 inch catback with the spintech rectangular muffler and it sounds pretty good , pretty mellow driving around .

The Alchemist

iTrader: (19)

Well, painful story. Went to LS FEST this year in Bowling Green. Drove from my house there, about 800 miles, and no issues. Didn't race the car at all, and coming home, about 4 hours out, 1am, it snapped a rod cruising at 1700rpm. I had forged SCAT H-beam rods and #7 snapped, and I have 3-4 others that have signs of bending. Still haven't determined what happened. SCAT thinks that since my pistons were 0.005" out of the hole, that they hit the heads and bent the rods, but the pistons are all fine, except for the one with the snapped rod. The heads are fine except for a bent exhaust valve where the rod took out the lifter.
So who knows. I had 4,000+ miles on the motor without incident. It made good power, didn't eat oil or coolant, so I don't know. At this stage, I'm just moving forward.

Did you custom make that or buy it as a kit?

The Alchemist

iTrader: (19)

Here's one of the rods that is bent:



And here's the snapped rod:

conan

iTrader: (5)

Sucks to hear man, not the reply I was expecting to see... Good luck with the ls3 transplant.

I have been kicking around this idea for a while with my exhaust and might give it a go this winter if the cost isn't too much... I was thinking about getting a Flowmaster 4" merge for my Kooks Y pipe and then replacing my Hooker 3" I pipe with a 4" pipe that necks back down to 3'' at the end. Place a 4" cut out in the I pipe right before the axle and then reattacing the Hooker catback. I like the idea of placing the cutout in the bump out of the body by the rear passenger seat.

Just a thought, It will be snowing here soon so I'll post something up if I give it a go.

Rise of the Phoenix

iTrader: (27)

What is the price difference between the 1 7/8 and 2" headers? I would personally go with the 2" headers, as long as they are not un-godly more expensive.

On a side note, will you be putting your existing PI heads on the LS3 motor, or opting for LS3 style heads?

ramairetransam

iTrader: (18)

came with the car . http://www.mufflex-performance.com/1...k-exhaust.html

i dont know if its cheaper anyplace else but to give you an example

The Alchemist

iTrader: (19)

Well, I plan to continue to run my PI heads. I will have them opened up to take advantage of the increased bore, but not much else. Out of the box, they flow well, so I'm fine with them at this stage.

Cool28

iTrader: (2)

I like my kooks 1 7/8 headers and true duals but it is loud no missing ya coming down the street lol.

Hope I get to see the car in the spring if mines not broke again lol

Rise of the Phoenix

iTrader: (27)

Yeah, since you already have them, and they are un-damaged, might as well use them because they are some pretty impressive heads. Who are you going to have open them up?

No Juice

iTrader: (11)

You're in the same boat as me. I personally like the sound of the Magnaflow too much to give it up. 1-7/8 should be plenty. The consensus I keep hearing is adding dual cutouts

LS1RedZ

iTrader: (19)

I would def do the 1 7/8 headers. Too bad they don't make them with a 3.5 collector. Or do they? Then do 3.5 into the magna flow with a single cutout before.

Rise of the Phoenix

iTrader: (27)

I'm curious why everyone is so against the 2" primary 3.5" collector headers? A Procharged engine needs to move a ton of air, so I see a great benefit to going with the bigger headers and bigger exhaust. I really don't see a single downside other than the cost, but $47.20 is a drop in the bucket considering the cost of his entire setup (Prices were obtained off Maryland Speed's website). Plus, I'm pretty sure he's going to step up to a bigger head unit at some point in time, so the larger headers and exhaust will be an even greater benefit at that point.

Tally TransAm

iTrader: (17)

2" without question

conan

iTrader: (5)

Are you running 1-3/4" or do you already have 1-7/8" headers. If your still on 1-3/4" and this is a vote between buying 1-7/8" vs 2"... I vote go with some 2'' Kook's.

Rise of the Phoenix

iTrader: (27)

In the OP, it says "original QTP headers". I'm pretty sure they only offered a 1 3/4 size in those, so my opinion is based on the fact that he's going to have to buy a new set of headers anyway, so might as well spend the extra $47.20 and get the 2" headers. If it were the case where he already had a set of American Racing or Kooks 1 7/8 headers, then I'd suggest he just roll with them.

The Alchemist

iTrader: (19)

Sorry I didn't give more accurate information up front. Yes headers are currently 1 3/4" variety. I had spoken to some people, and cam selection is more critical than header size from what I've seen.

If I go with 1 7/8", I have a fair amount of choices, but 2" and I'm going Kooks.