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Old Mar 10, 2006 | 02:59 PM
  #1  
DocHoliday's Avatar
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Gotta muffler question...

I have looked everywhere imaginable to find a muffler that has a 3 inch inlet and dual 3 inch outlets. I can not find one. All of them I find are 3 inch in, dual 2.5 out. Will having 2.5 inch outlets restrict my exhaust or cause me to loose power? If not then I know what catback I am getting. But if so, please point me to a muffler with 3 inch inlet dual 3 inch outlets. Thanks!

DH
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Old Mar 10, 2006 | 03:09 PM
  #2  
Aredross's Avatar
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From: Montgomery Alabama were not *******s
Car: 1990 RS coupe
Engine: TBI 305.
Transmission: 700R4
I dont believe the pipes after the muffler being a half inch smaller would effect performance in anyway............And Im pretty sure im right
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Old Mar 10, 2006 | 04:42 PM
  #3  
IROCThe5.7L's Avatar
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Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
Summit use to have an 80 series that was 3' in and out. Now it's not listed. Might want to try and email them.
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Old Mar 10, 2006 | 09:03 PM
  #4  
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From: Pittsburgh & Allentown PA
Car: 1992 Z28 (Heritage Edition)
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 2.73 Posi
i seriously doubt it matters. Your I-pipe (in. diameter) is 3 in., but you have two 2.5 outlets. so thats probably equivilant to a single 5 inch muffler exit; that makes any sense.

Dont worry. Two 2.5 in. oulets will not cause a problem.
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Old Mar 11, 2006 | 04:40 PM
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From: Brighton, CO
Car: '72 Chevy Nova
Engine: Solid roller 355
Transmission: TH350
Axle/Gears: 8.5" 10-bolt 3.73 Posi
Two 2.5" pipes outflow a single 3" pipe. Don't worry, it's fine.
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Old Mar 13, 2006 | 01:01 AM
  #6  
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From: Surrey, BC
Dynomax's Ultraflo line had a 3" in dual 3" out.

But as said before, it really wont make a difference at all.
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Old Mar 14, 2006 | 12:12 AM
  #7  
DocHoliday's Avatar
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Cool, well then it looks like I can buy a catback without any problems.
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Old Mar 14, 2006 | 05:36 PM
  #8  
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DH, that 84 is in beautiful shape! How many miles are on it?
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Old Mar 19, 2006 | 03:14 PM
  #9  
DocHoliday's Avatar
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Its got a little over 108,000 on it. Bought it with 107,XXX. Its just been my to and from school and work car. Im a teenager so thats all I need it for really. That and whatever errands I have to run. Thanks for the compliment.

DH
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Old Mar 19, 2006 | 04:38 PM
  #10  
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From: Pittsburgh & Allentown PA
Car: 1992 Z28 (Heritage Edition)
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 2.73 Posi
Originally Posted by DocHoliday
Its got a little over 108,000 on it. Bought it with 107,XXX. Its just been my to and from school and work car. Im a teenager so thats all I need it for really. That and whatever errands I have to run. Thanks for the compliment.

DH
I know this is alittle off topic, but doc it looks like your car might have been hit in the front or something? I'm pretty sure you said that it still had original paint, and in that pic you can tell the front bumper area is darker than the rest of the car, and the striping on the ground effects seems to be slightly different than the rest of the car... Do you have any idea why that is??
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Old Mar 20, 2006 | 09:15 AM
  #11  
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Originally Posted by a mack6
I know this is alittle off topic, but doc it looks like your car might have been hit in the front or something? I'm pretty sure you said that it still had original paint, and in that pic you can tell the front bumper area is darker than the rest of the car, and the striping on the ground effects seems to be slightly different than the rest of the car... Do you have any idea why that is??
Yeah I know it looks different, but I am almost positive it is from paint fade. The bumpers plastic and the bodys metal, so it fades differently. Its also an Arizona car and the sun is relentless. Thanks for your concern, but from how this car was kept over its life, I can gurantee it wasn't hit. I got all maintenence records also. Thanks!
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Old Mar 21, 2006 | 02:00 AM
  #12  
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Car: 1991 Z28
Engine: 5.7L LT1
Transmission: 4L60
Two 2.5" tail pipes DO NOT out flow a single 3"! If you ran a 3" cat back into a single 3" bullet and one tail it would hammer and I mean hammer ANY expensive 3" inch exhaust on the market when it comes to flow! This dynomax setup can be had on summitracing for like $240 shipped! The proposed exhaust has to be routed through the muffler then into the tails and out. THis slows its exit down! All this is bypassed with a single straight through 3" bullet. Draw a picture and it all becomes obvious instantly which is the superior setup. But having said that, the two 2.5" tails will suffice. I wouldn't worry about it. Just get a muffler that is straight through and NO flowmaster! With one of them your exhaust might exit sometime next week, they are junk! and sound like junk as well! Sorry boys, its true. Its amazing what an extensive advertising campain can do!
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Old Mar 21, 2006 | 03:03 AM
  #13  
IROCThe5.7L's Avatar
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From: Buffalo, NY
Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
Yea, don't get a flowmaster. If you get any other brand, i'm sure you will run atleast 2 seconds faster in the 1/4.

It appears that your car is mostly stock. Just get whatever sound you like the best. There is a sticky on top of the page of sounds. Good luck!
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Old Mar 21, 2006 | 12:43 PM
  #14  
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Could not agree more. I swapped out my single outlet FM, and replaced it with a Dynomax UltraFlow, and the car picked up one tenth, and one MPH.
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Old Mar 21, 2006 | 04:58 PM
  #15  
DocHoliday's Avatar
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Well I'm also getting a cut out before the cat so I guess it is just up to what sounds the best. And yeah, I wasnt planning on getting flowmaster. Heres the setup I am going to be running:

Hooker 2055's Headers and y-pipe
QTP 3 inch Electric cut-out
Catco High Flow Cat (9118)
Pacesetter Catback

Could an exhaust shop get all of this to fit? They might have to shorten the I-Pipe. Thanks for your guys help!

DH
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Old Mar 21, 2006 | 10:17 PM
  #16  
Crusin' 1980's's Avatar
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From: Upstate New York
Car: 1988 SC Camaro
Engine: 305 TBI
Transmission: 700-R4
A shop probably could, if money is an issue, you should keep in mind that the part you listed, plus labor at an exaust shop will probably run you well over $1,000.00 bucks...also, some shops won't remove and replace your orginal cat unless there's something wrong with it because of certain states emmissions/environmental laws. Maybe someone else can add onto this...
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Old Mar 22, 2006 | 12:38 AM
  #17  
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Car: 1991 Z28
Engine: 5.7L LT1
Transmission: 4L60
I believe that is true. I don't offer anything that can support such a claim, But I have heard that it is illegal to remove or replace the cat unless it isn't functioning properly. I think its a grey area that really isn't policed. Just do it and if anybody calls you on it just say that it needed to be replaced LOL!
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Old Mar 22, 2006 | 12:23 PM
  #18  
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From: North Carolina
Car: 1987 Pontiac Trans Am GTA
Engine: 5.7 TPI, L98
Transmission: 700R4
Axle/Gears: 3.42:1
Flo-Pro make a good muffler that is cheaper than most.

I just had exhaust finished out on my car. I used 2.5" true duals with 2 cats. The whole job, pipe, two new FLo-Pro mufflers, two "used" cats, two oval chrome tips, and labor was only $350. I didn't get an itemized bill, so I don't know exactly how much I paid for the mufflers, but they must have been cheap.

There may be others that are better performance, but these sound good and are cheap. I've had a lot of compliments on sound, so I'm satisfied. I also picked up 1mpg.

They make a 3" in and 3" out. That is what I have on my truck. Bought them used for $30 for the pair.
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