L03 EXHAUST INFORMATION

Background

Exhaust mods are probably the most common for Thirdgenners, because they are relatively easy, cheap, and make a pretty big difference in sound and performance.  There are basically four parts of the exhaust that you can upgrade, the manifold (manifolds or headers, and y-pipe), the catalytic converter, the cat-back (intermediate pipe, muffler, and tailpipes), and the muffler separately.

Exhaust Modifications

Manifolds & Headers

You can go with an upgraded manifold, such as the manifolds found on L98 cars, which will flow a little better than stock, and still keep the stock appearance.  They don't however, make a huge difference associated with headers.

Headers will give you the biggest gains that any other part of your exhaust system.  The engineers that designed out cars didn't leave us that much room to play with as far as headers are concerned.  Because of that, almost all headers available for Thirdgen F-Bodies are the "shorty" type - they are short tubes, usually unequal in length.  Headers com in all shapes, sizes, finishes, and materials.  For our cars they are usually 1 5/8" - 1 3/4" primaries with a 2 1/4" - 3" collector or y-pipe.  1 5/8" is good for a 305, but for a performance  350, it is recommended to go with the 1 3/4" primaries and at least a 2 3/4" collector.

Here are the components that make up an SLP header/Y-pipe combo.  These headers don't have provisions for the A.I.R. system.

This is the Y-pipe.

Here is a picture of SLP headers and Y-pipe assembled (no A.I.R.).

Here is another pic of SLP headers, but these have the plumbing for A.I.R.

The usually come plain old steel with a shot of protective paint on them, but are available stainless steel.  Plain steel will rust eventually, and the paint that they put on them will burn off almost instantly when the engine is started the first time, making a big mess and a big smell.  I recommend the stainless steel ones, because you don't have to worry about corrosion.  They also look better in my opinion.

Catalytic Converter

There are a basically three ways to handle the cat.  You can either get a high flow aftermarket unit ($$$), you can take your off, and hollow it out (doesn't flow well), or you can have somebody make you a replacement pipe that will take the place of the cat.

Cat-Back System (Intermediate Pipe, Y-Pipe, Tailpipe)

A cat-back system is the most common upgrade to a Thirdgen exhaust system.  It is one of the easiest, and relatively inexpensive most of the time.  The cat-back includes what it's name implies...everything from the catalytic converter back.  This includes the intermediate pipe that goes from the cat to the muffler, the muffler, and the tailpipes.  Most cat-backs are direct bolt-ins.  They come pre-made and ready to install.  Most of the time they bolt up to the cat and use all of the factory mounting locations and hangers.

There is a big difference between stock intermediate pipes and the aftermarket cat-back types is not only in the size and material, but the way that they are bent.  Most stock exhaust pipes are non-mandrel bent.  As they are bent, the inside of the pipe is "corrugated", and the diameter is greatly decreased.  Also the inside of the bend is so irregular that it messes up the flow of the exhaust gas.  A mandrel bent pipe is bent using a mandrel (duh) which does not have these problems.  It keeps the diameter of the pipe constant throughout the bend, and keeps it smooth.  It's not hard to see what will flow better.

Here's a picture of an SLP cat-back system.  You can see that the diameter of the pipe is constant throughout the bends.  You can also see where the mounting tabs are welded to the pipes so that they bolt up to the factory hangers.

Muffler

Even though the muffler comes with a cat-back system, it's also pretty common to get a new one.  Whether it is for a different sound, or better flow.