3.8L FBODY BASIC EXHAUST OVERVIEW

Thanks to all the helpful (and patient) forum members (ellik/blldog to name just a few) who helped with my initial understanding of our stock exhaust systems and some of the basic differences in the various aftermarket cat back kits and their respective ‘model years’ that are available for the L36 Camaro/Firebird. If any of the following information is incorrect it is not their fault, but rather this authors. This page is intended as a basic overview for those of you who are just getting started in modding the exhaust system of your car. Please follow up with your own research regarding your particular year vehicle, engine type, intended aftermarket system, etc., as well as any emissions requirements your particular state may have.

Basic

The stock exhaust system for the 3.8L F-Body is 2.25” ID

The stock Y pipe terminates (welded at factory) at the catalytic converter and is 3” ID.

The stock CAT is 3” ID in and 2.25” ID out.

The stock S pipe has an O2 sensor boss for the rear O2 emissions sensor.

The stock S pipe is 2.25” ID as is the rest of the exhaust piping from that point on up to the muffler ‘IN’ port.

The stock tail pipes…if you have stock dual tips are 2.0” ID at the muffler ‘OUT’ ports.

Mandrel Bent: Mandrel bending allows the piping to retain its full diameter through bends. This is much preferred over non mandrel bent pipes. Non mandrel bends severely crimp and pinch the pipe through bends and this greatly reduces the ID of the pipe. Most muffler shops DO NOT have a mandrel bender. Name brand aftermarket catback systems feature mandrel bend pipes.

Dedicated (designed specifically for) V6 cat back systems are 2.5” and typically start AFTER the S pipe. They are made for your specific year of vehicle so they require no further modifications. They are the easiest to install and should come with everything you need.

3” cat back systems are originally designed for the V8 F-Body but can be easily adapted for use on the V6 F-Body car.

Not all 3” (v8) cat back systems come with an S pipe. (model year dependant)

V8 tail pipe hangers are different than v6 tail pipe hangers.

Not all cat back systems come with transverse ‘under gas tank’ oval muffler. Some (such as the SLP LM) come with a bullet style ‘resonator’ that usually mounts inline in the mid pipe.

Not all cat back systems feature dual tip exhaust.

Aftermarket CATs have collars that slip OVER the appropriately sized exhaust pipe. Example…The stock Y pipe is 3” ID. A 3” in CAT will slip over the Y pipe…to be clamped or welded. If you have a 3” ID S pipe…a 3” out CAT will slip OVER the 3” S pipe to be clamped or welded. Get it? In other words…muffler and cat diameters are sized with ends that will read 3” or 2.25” etc., but the ends have collars that are slightly bigger than that diameter as they are intended to slip over the respective 3” or 2.25” main exhaust piping.

We use 12” oval cats on the 4^th gen F body. Some manual transmission cars require an Air Tube…auto trans cars do not. Our rear ‘O2’ sensor boss is in the factory S pipe. Depending on whether or not you plan of doing a full 3” conversion or if you are adding a ‘built for your year v6’ cat back you may need to add an O2 sensor boss to your list of parts. The sensor boss can be welded in to the S pipe by pretty much any muffler shop. Another option when doing a full 3-inch conversion is to order a universal 3x3 cat with rear O2 sensor boss. I used a magnaflow/carsound universal 12” oval 3”x3” no air tube #94039…not for California…about $75. Whether or not you plan to SIM your O2 sensors…you still need to look official, right?

Heavy Duty U-bolt clamps: Just as titled these babies are heavy-duty clamps. I got mine from NAPA for $4. They have a retainer welded on the pressed metal clamp portion to inhibit spreading. (see fig. 1)

Hangers: Specific systems for your specific year vehicle should (in most cases) also come with the appropriate style tail pipe hanger mounts for that particular year. If you plan on converting different year/engine type (v8 to v6 for example) cat backs to your v6 you will most likely need appropriate ‘stock’ chassis hanger mounts for that year/engine type or you can use universal hangers or possibly adapt/convert what you already have. This is nothing that you can’t work out with a little effort and a trip to your local parts store. You can even rig something up that is safe but temporary and then use your old hanger mounts and have a muffler shop weld those on appropriately for your new system if you are doing the main work yourself and don’t have welding equipment. (see fig. 2)

Bullet Muffler (or resonator): If you are using a standard F-body exhaust system that features a transversely mounted oval muffler mounted under the gas tank then you may also be interested in adding a ‘race ready’ high flow bullet muffler in the mid pipe section of the exhaust system. (see fig. 3) I have had great results with a Dynomax 18” bullet. They also come in 12” length. My current system is 3” so I ordered a 3” bullet. The end collars just slip over 3” exhaust piping and are then welded or clamped. This thing is just a hollow ‘perf tube’ that does not inhibit performance to any noticeable degree if at all but it does deepen the overall tone of the system as well as reduce high-end raspiness to a substantial degree. They are rather affordable (about 30 bucks or so) and can easily be found at summitracing.

General

Let’s start off with some basic ‘reviews’ and general opinions that you might find if doing an in depth search on aftermarket exhaust systems for our cars:

Bigger is louder. The fatter the ID of the main exhaust piping the louder your car will be. When you also consider that you are putting on aftermarket…hi-flow / hi performance exhaust systems then figure for even louder than loud.

If for some reason you remove the catalytic converter…. figure on more loudness and a much harsher overall tone.

Going for a cut out? Then you don’t need my help.

Upgrading to headers? Yes, better breathing = louder but generally improved performance sound as well. What performance enthusiast doesn’t appreciate headers? No direct support for headers here, though, but perhaps some of the following basic cat back info will be of help. Well, one thing I will say is that if you have a 2000+ model year car then you have tubular manifolds from the factory. These babies are very nice. If you have em…you can move headers much further down your list of mods as they already flow very well. They can handle a lot of major upgrades such as valvetrain/cam, P&P heads and Superchargers.

What do different mufflers/systems sound like? Well, you are sorta on your own for sound bites and stuff. If you have found my Project Unleashed website then you already know how to find some specific camaro/firebird v6 exhaust sound clips. The only VERY specific info that will be given on this site concerns the installation of a 3” Magnaflow V8 LT1 cat back system on a 2001 v6 Firebird.

Emissions:

With an emissions related SES code popping up you will not pass OBD2 emissions tests in your state. Some states even visually inspect during the emissions test….under car…looking to see that all sensors are where they should be, etc. It would be best to know beforehand what is involved in passing and the testing procedures in your state before making serious modifications to your exhaust system.

You will often times set off a SES code when you change from a 2.25” out cat to a 3” out cat. I do not know for sure about going to a 2.5” out cat.

Headers = SES code. In other words…don’t be surprised.

If you are going from a stock 2.25” system to a 2.5” cat back system sold for your year vehicle...(not including headers) you should be ok. It seems that most of the emissions (OBD2) problems come from the more extreme 3” full systems.

The above info is either my personal experience or what seems to be a general consensus regarding these issues.

This website will not get involved in the “is 3in. exhaust better than 2.5in.” exhaust debate. It will be assumed that you already know what you want out of your car and what kind of modifications you plan for your over all project and performance goal. The more fuel and air you put into the engine the more exhaust gases that need to be expelled from engine.

Catback Systems – What fits what?

I cannot possibly cover every combination of 4^th gen v6 F-Body and all the different cat back systems. There are some basics, however, that should help nail down what you get with basic cat back systems for given year vehicles….for both ‘designed for’ the v6 and ‘designed for’ the v8 aftermarket systems. The V8 option is very important here as they represent a wide range of 3” system kits that may or may not include everything you need for a complete conversion to a full 3” system.

Once again…I do not have experience with EVERY brand/year/v6-v8 cat back. You should also visually inspect your exhaust system. It may have already been modified, etc.

Conversion vs. Replacement: Most all v6 cat back systems (2.5”) sold for your particular year vehicle will come with everything you need to complete the project. (see fig. 4) The tail pipe hangers will be correct and the actual exhaust piping will bolt right up to what is already on the car. You will still have your stock 3”x2.25” cat and probably the stock 2.25” S pipe as well…with the new system starting post S pipe. You should not have a problem with emissions and there should be some performance gains.

If you plan on going with a full 3” system then consider it as a conversion. There is no full 3” system built for the v6 F-Body…. but some kits will get much closer than others in providing everything you need and you can also purchase a 3” conversion kit to adapt some systems to your car. This is where it becomes handy to know what year cat backs… v8/v6 come with what components, etc.

1994-97 v6 and v8 F body. These cars came from the factory with a FLANGED CAT. Whether or not the CAT is welded to the Y pipe is no big deal…BUT on these year cars the S pipe is connected to the CAT with a 2-bolt flange. In other words…the cat is not welded to the S pipe but rather bolted. The S pipe is then band clamped to the mid pipe. (or intermediate pipe) Therefore these model year systems will often times come with an aftermarket S pipe. (see fig. 5)

1998-2002 v6 and v8 F Body. These cars come with the CAT welded to the Y pipe and also welded to the S pipe. The S pipe is then band clamped to the mid pipe. Since these years of cars use a welded S pipe these year cat back systems will often times not come with an aftermarket S pipe. This is where something like the SLP 3” conversion kit is handy. (see fig. 6)

3” Conversion Basics

Converting to a 3” exhaust system is the most involved option as far as additional modifications and additional parts that will be required. A conversion such as this is, however, quite easy to perform. The least involved method as far as extra parts is concerned are many of the LT1 V8 cat backs for 1994-97 V8 F-Bodies. On those year cars the CAT is attached to the S pipe with a 2-bolt flange so those systems often come with a 3” S pipe. The S pipe will not have a 02-sensor bung but as mentioned earlier you can weld one in or get a cat that already has a rear O2 boss. You will also need a 3x3 cat to mate up correctly. Just cut the flange off of the new S pipe and the 3” out cat will slip right over. The tail pipe hangers will not match your stock hanger mounts…this is where universal hangers come in. Just use the chassis bolts/holes from your old stock mounts to attach the universal hangers to the chassis or find some v8 chassis mounts or save your original hangers for integrating in the new system.

Find out all that you get as far as components from any giving cat back system. Some will require a 3” conversion kit such as the one sold by SLP.

Horizontal S pipe hanger: If you change to a 3” S pipe the stock tranny/exhaust horizontal hanger will have to be removed. There is ‘shock absorbing’ main mount that can still be used, however. To see an example of a custom replacement see figure 7.

Check out my page detailing the removal of stock exhaust system and installation of the Magnaflow #15620 1994-97 LT1 V8 cat back system complete with 3x3 cat and a rasp inhibiting 18” Dynomax bullet muffler in the mid pipe HERE.

What Comes With What?

Magnaflow 15620 LT1 V8 (1994-1997) Comes with 3” S pipe but will need tail pipe hanger modification as well as custom S pipe horizontal hanger. VERY EASY.

Hooker LT1 V8 (1994-1997) cat back comes with an S pipe. As with other V8 systems the tail pipe hangers do not match the V6 system. Check out the Hooker LT1 install and review by ‘black98V6’ HERE

Magnaflow (and most all other???) LS1 1998+ cat backs do not come with a S pipe.

It is unknown what other LT1 (94-97) cat back brands come with a S pipe. 3” catback systems that don’t come with a S pipe will need to have one made or purchased.

SLP Installation Kit: This is mainly a stainless steel 3” S pipe. It is needed when you do not get a 3” S pipe with your particular Cat Back system yet you want to use a 3x3 cat and convert the exhaust to a full 3” system. Unfortunately for some it does not come with an O2 sensor bung welded in it. You will have to have that done separately if you do not get a CAT that has a rear O2 bung already in it. In the picture below you can see how one end is flanged. You can cut the flange off and a 3” CAT will slip right over it. The other end is ‘crimped’ to a smaller diameter so that it will fit into a 3” mid pipe. Part Number is: SLP-30045 - Installation Kit, 1993-02 V6 F-Car $72.95 http://www.ftpp.net/V6Main.htm

Tbyrne also has the SLP installation kit… http://www.tbyrne.com/v6catalog.html

As well as LMPerformance: http://www.lmperformance.com/1576/2.html

NOTE: There is a cheaper (about 30 bucks) SLP install kit. That kit is just hangers and does not include an S pipe.

Jegs has a more affordable option for an S pipe. They have a 3” mandrel bent U Pipe for about $30 I believe. The U pipe can be cut and welded into an S shape quite easily. The end that mates with a 3” mid pipe may need to be crimped down in diameter…or a slip over collar may have to be welded over the connection, for example. I never used this ‘u pipe’ solution and have never seen it. This might be it…please double check before you purchase…

642-10719 Magnaflow Exhaust J BEND 180 DEGREE 3'' $25.99 http://www.jegs.com

Example of an O2 Sensor bung: $10 at http://www.lmperformance.com/1783/2.html

Most muffler shops should already have this item.

Magnaflow / Carsound universal 12” oval 3”x3” no air tube w/ rear O2 sensor boss #94039…not for California… $75 bucks. http://www.bestautopartsonline.com/94000CONVERTERS.html

O2 Sim: Caspers rear O2 simulator: $45 182-104035 GM 1997-02 w/One Sensor $44.99

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=120328&prmenbr=361

Summit racing also has the casper sim as well as zzperformance and many other shops.

FIG 1 FIG 2

FIG 3

FIG 4 (note the different part numbers. Welded CAT year cars will not come with a replacement S pipe)

FIG 5 (notice how this model year kit comes complete with a replacement S pipe)

FIG 6

FIG 7

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