Okay, I need to gain some understanding here. My car is a 93 GT that is completely stock with the exception of some 3 chamber Flowmasters installed by the previous owner.
Can someone help me understand all of the components of my dual exhaust system. I'll write down what I know, and you tell me where I went wrong:
1. From the Heads: I have factory exhaust "headers" or manifolds. These are quite short and only go about 6-12" down into the engine bay.
2. From the end of the factory headers, there are clamps and pipes heading under the car. I assume this piece is connected to the one on the other side of the engine as well and eventually stops right before the catalytic converters.
3. Next are two catalytic converters. One on each side.
4. After the cat (I assume there is only 1 per side?) there is an individual pipe that goes back under the car to the muffler. One per side.
5. There are two mufflers. Mine are flowmasters, but appear to be just about the same in size as a stock muffler.
6. After the muffler there are pipes that go up and over the rear axle then out to the back of the car. I have a GT so my pipes point straight down under the plastic at the rear of the car.
Questions:
1. I live in a state with emissions check. I assume that means that I cannot remove my cats?
2. I plan on adding aftermarket headers fairly soon. Due to the age of my exhaust system (about 12 years old) and the miles on the car (115K) I was considering replacing ALL of the exhaust system. All the way from the headers to the end of the car. Is this doable? Cost? Options w/ cats?
3. I also plan on replacing the factory 5.0L heads and intake system at the same time. If I get brand X head (not sure yet which, but prefer aluminum), do I need to get headers to match the heads?
4. I still don't understand the short versus long headers. Why NOT put the long headers on the car if I'm replacing everything. Can I do this and still have a cat?
5. Do I need BIGGER cats if I'm planning on having about 350-400 HP in the next 12 months?
The exhaust consists of three items: Headers, H-pipe, and catback.
You've got the headers which connect to the Hpipe via a ball and socket
type joint secured by two studs.
The factory H-pipe will have four cats on it; the two small ones at the front,
and the two larger ones at the rear (these receive thermactor air via a met-
al tube). You can get new H-pipes without cats, or with high flow cats.
From there on back is the catback portion - basicly your two tailpipes.
You probably would be better off replacing everything at once. Try shopping
online, or pickup on of the many Mustang magazines.
I've heard of people passing the sniffer without cats. Ohio used to visually
inspect for them, but now I think they've tightened up the sniffer standards
enough to the point where it's really hard to pass without them. Talk to
other motorheads in your area, see what they're doing about inspection.
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1992 Deep Emerald Green Mustang GT Hatch, 5 speed, 2.73s, Mac fenderwell cold air intake, '93 Cobra MAF, Mac 70mm throttle body & spacer, Explorer intakes, Mac unequal headers & offroad pipe, Magnaflow catback, Walbro 110lph fuel pump, Jet adjustable FPR, MSD Blaster coil, Accel 8mm wires, FRPP aluminum quadrant, UPR firewall adjuster, stock cable, Granatelli upper control arms.
Waiting to go on: Granatelli lower control arms, and GT40 Iron heads!
If you are going to replace the entire exhaust system, you should go with longtube headers with a set of high-flow cats in an h-pipe. The longtubes create more low-end torque over the shorties, while the shorties poduce more top-end power. If you decide to go with the longtubes, consider buying a well known brand because the fox bodies sometimes have collector to floor clearance issues and/or primaries to firewall clearance issues. I would also go with a 2 1/2" exhaust system. If you plan on getting into the 600+hp, I would probably go with a 3" system.
The exhaust consists of three items: Headers, H-pipe, and catback.
You've got the headers which connect to the Hpipe via a ball and socket
type joint secured by two studs.
The factory H-pipe will have four cats on it; the two small ones at the front,
and the two larger ones at the rear (these receive thermactor air via a met-
al tube). You can get new H-pipes without cats, or with high flow cats.
From there on back is the catback portion - basicly your two tailpipes.
You probably would be better off replacing everything at once. Try shopping
online, or pickup on of the many Mustang magazines.
I've heard of people passing the sniffer without cats. Ohio used to visually
inspect for them, but now I think they've tightened up the sniffer standards
enough to the point where it's really hard to pass without them. Talk to
other motorheads in your area, see what they're doing about inspection.
Great explanation. I kept hearing the term "H Pipe" but I wasn't sure what that was. Now I know.
I am more inclined to keep the cats for several reasons. One: They are good for the environment and as corny as that sounds to some, it is somewhat important to me. Two: If I ever move, or sell the car to someone who lives in an area where they need Cats, the car will have them. I will begin to search some of the Mustang rags I've picked up ("Mustang 5.0 something" and also "Muscle Mustangs & Fast Fords") and look for cat H pipe systems.
Okay, no one has yet answered the question on headers: IF I change the heads to brand X, do the aftermarket headers need to match this? I.E do the new heads have bigger or different shaped exhaust ports? I'm assuming they would be bigger.
Second: What is the difference between 2 chamber and 3 chamber Flowmasters? I have the quieter of the two but not sure which it is. I love the sound of my car.
Third: Is the Borla SS exhaust better in any meaningful way other than it will last longer because it is stainless steel?
the only two types of heads that i'm aware of that wont work with EVERY header is the Gt40 p? and the Trickflow highports... other then those two heads i'm pretty sure every header will work.
if you have a manual long tubes are more available for your car if its an auto it can be expensive!
if you want cats get high flow cats in an h or x pipe and yes 2 chamber flowmasters are louder than 3 chamber ones i prefer the 2's thats what i run and gives it a good sound hope that helps ya good luck :thumbsup
oh yea my header back to the tailpipes ran me about $700 if your going for cats plan on spending a 100-200 and if your in search for long tubes... even more...
Fox Exhaust Systems - Questions 
