Time to do some exhaust work on my little 305. I already have an aftermarket muffler, I think it is a Dynomax, so it is not stock. Anyways, I was wondering what would give the best performance gains/loudness for my TBI. What should I be looking to spend? I am looking to make my car sound meaner and get as much performance as possible. Any help is appreciated.



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1991 Pontiac Firebird
51k Miles
T-Tops
Fire Engine Red
305 TBI
14" Edelbrock Element
"Pure Crempuff"

 

Im going for Hooker Shorty Competition Headers($141 from Summit) and getting them Jet Hot coated(around $150-$200). Im also going with a 3 inch Flowmaster American Thunder cat-back with stainless steel tailpipes($316 for dual exit)...and a 3in inlet/outlet Catco highflow cat($116).

Overall, probably about $700-$750 for 3 inch exhaust all the way back...Ohh yeah...I cant wait!

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1987 Camaro Sport Coupe 305 V8 LG4-rebuilt-All Stock.

Future Mods: Flowmaster American Thunder 3 in. Cat-back, Catco High Flow Catalytic Converter, Hooker Super Comp Shorty Headers Jet Hot coated, K&N Air Cleaner, CompCam 264H, White Paint, IROC wheels, Alpine CDM-7871 CD player, Polk Audio speakers, Grant GT Rally Steering wheel,New Fuel Pump, Ground Effects, B&M Megashifter

 

Ok, well I'm only gonna go with one or the other to staryt off with, which should it be? what are the advantages/disadvantages for both? Thanks.



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1991 Pontiac Firebird
51k Miles
T-Tops
Fire Engine Red
305 TBI
14" Edelbrock Element
"Pure Crempuff"

 

*** knows our cars probably have the worst exhaust, period. I would start off with a cat-back because if you have a good set of headers but stock exhaust, it wont do you ALOT of good.

Get a 3 inch cat-back and a 3 inch high flow cat...all mandrel bent pipes...

Im not sure what headers you should get. Depends on how far you are going to be modding your car. Im going with 1 5/8 primarys into 3 in. collectors. But if you are turning your car into a real performance machine, go with some 1 3/4.

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1987 Camaro Sport Coupe 305 V8 LG4-rebuilt-All Stock.

Future Mods: Flowmaster American Thunder 3 in. Cat-back, Catco High Flow Catalytic Converter, Hooker Super Comp Shorty Headers Jet Hot coated, K&N Air Cleaner, CompCam 264H, White Paint, IROC wheels, Alpine CDM-7871 CD player, Polk Audio speakers, Grant GT Rally Steering wheel,New Fuel Pump, Ground Effects, B&M Megashifter

 

Yeah I'd definitely go with the cat back first. The dyno max muffler isn't doing you as much good if it is still breathing through stock-for-TBI 2 1/4" pipes. I would go with a 3" mandrel bent system from the manufacturer of your choice (opinions vary, do a search and you'll see). Benefits are better sound, and increase in power (albeit a small one), lower cost and easier install than headers. Plus the benefit of headers are not entirely realized unless you have a good after cat system.

 

I have to agree with the rest of the people. You would be best to start with the cat-back system first. As someone said in another post one time, if you put headers on a car with stock exhaust, you are doing nothing more than moving the cork further back.

You are not going to get the sound you are probably looking for with just a cat-back, but by putting headers on with it dumping into stock exhaust, the performance isn't going to increase a great deal. The sound would probably increase and sound meaner, but not like it would if you start with the cat-back system and do headers later. So in general, I would say, your best bet overall is the cat-back.

Matt

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irocet@hotmail.com

drive.to/Stang_Kilr

88 IROC-Z -- 350 L-98, 700R4, Flowmaster, Edelbrock Headers, Catco Cat, K&N, MAF Sceens Removed, Airfoil, March Pullies, Comp Cams Magnum 1.6 Roller Rockers, Bosch Platinum Plugs, Accel 8.8 mm Wires, MSD 6AL, Hypertech Cap & Coil, Hypertech Chip, Hotchkis Strut Tower Brace

 

No way, one of the biggest hinderances of our cars is the stock exhaust manifolds. Get yourself some headers. That cat-back won't do a bit of good without the flow of exhaust thru some headers. That's why most people make headers their first major mod.

------------------
"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

Oh forgot to mention, if you look at the stock y-pipe it's horrible the angle of the bends really hurt the flow so headers w/a new y-pipe is the way to go. Besides with a near stock motor and TBI 3" exhaust won't improve you too much over your stock size.

------------------
"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

Im going to agree with the majority here.
The headders will help but if your restricted down the line they wont do much. Get the cat back done 1st then headders if possible just save and get it done all at once.
SSC

 

Yeah im just saving up and modding mine all at one time.

Hooker comp headers jet hot coated
3 inch inlet/out Catco high flow cat
3 in. inlet/outlet Flowmaster American Thunder Cat-back DOR Exit

I will probably add a new intake and air cleaner too. I can't wait to feel the major difference from bone stock to that.

------------------
1987 Camaro Sport Coupe 305 V8 LG4-rebuilt-All Stock.

Future Mods: Flowmaster American Thunder 3 in. Cat-back, Catco High Flow Catalytic Converter, Hooker Super Comp Shorty Headers Jet Hot coated, K&N Air Cleaner, CompCam 264H, White Paint, IROC wheels, Alpine CDM-7871 CD player, Polk Audio speakers, Grant GT Rally Steering wheel,New Fuel Pump, Ground Effects, B&M Megashifter

 

What good will it do then, you say you push the bottle neck down the line, I would rather have it down the line than in the middle.

------------------
"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

if i were you, id save and do it all at once, its easyer, just do it all in one shot

------------------
Trent
---Car---
89 Firebird/305 L03 TBI A4/t-tops
Open Element Edelbrock Aircleaner w/ K&N air filter/Summit Chrome Valve Covers
Edelbrock TES headers 3" out/flowmaster American thunder 3" exaust/Catco cat
---Stero---
Pioneer DEH-P730 Premium
Infinity 2way 4652 4x6's/Pioneer 4way ts-a6985 6x9's
profile cl640 110x4

 

Ok, looks like I will lean towards the cat back first, then the headers. How much HP should I expect from just the cat back? Thanks for the advice.



------------------
1991 Pontiac Firebird
51k Miles
T-Tops
Fire Engine Red
305 TBI
14" Edelbrock Element
"Pure Crempuff"

 

I'd say 10 hp, but with headers you'd get more. I would wait for some more knowledgable people to reply about this, like TAS or others. I'm sure they'll tell you to go with headers.

------------------
"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

ok I saw my name I got my headers before a catback or my 3" pipe. I was looking at that big 3" pipe thought "What the hell am I thinking trying to make this go to a 2.25" pipe". So I ordered 3" dynomax pipe as soon as I found the right one to order.

------------------
-Tas
'89 Formula WS-6

305, TBI, 700R4, P.A.W. 14x3 open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips, Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248)
Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options

[This message has been edited by Tas (edited November 01, 2001).]

 

Mark, the headders will not always make an improvment just by themselfs. When you have a restriction closer to the source and less at the exit more matter will flow through than vise versa because thier is more force at the source. I just installed headders on my truck that has duals with glasspacks and to tell the truth I noticed more power from installation of the duals on the stock manifolds over just putting headders on the system. I would say Figuratively a gain of 20hp from the duals on the stock manifolds and a gain of 10hp by installing headders on top of it.
Its user prefrence I personally would rather have the easy and effective cat back slaped on anticipating headders in the near future.

Either way people use Flowtech aluminum gaskets and save yourself's a headach later on.
SSC

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85 Camaro, 355/400 "drag car" in moth ***** 13.1@ 101mph on its last season run.
Plans: Possibly add N20 for next season.
82 Firbird, getting a beef injection 355/700r4 3:42 powertrax system.

 

There is no way a cat-back on our cars will outperform headers.

------------------
"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

One more point, that 305 ain't going to need much more than stock exhaust size anyways with the little bit of power it puts out, the stock size won't bottleneck it at all. You don't need 3" until you get around 250 hp.

------------------
"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite