csouth

I'm almost at the point in my build where I need to make some decisions on my exhaust. This is just a 455, C heads bored .030 with Comp XE262 Cam and Headman headers. I'm wondering if there would be any performance gained or lost by choosing a 3" exhaust? I was going to use the Pypes header back system with X pipe and Street Pro mufflers. I've always heard that a bigger motor needs to "breath". I'm not married to the idea of 3", so I can live with 2.5" if its the best for my application. Any advice or feedback would be appreciated.

70olds455

I don't know about the performance gains of 3" exhaust, but I know its going to be pretty loud. I have a 2.5" exhaust with the street pro mufflers on my 71 cutlass and its a bit loud at idle.

72w442

I have 2.5'' all the way back from manifolds with performance mufflers and it sounds great and flows very well, noticeable difference from the factory exhaust.My motor has c heads and the engle 20-22 cam.I hear there are some clearance issues with 3" exhaust.I have the pypes 2.5'' slip over stainless tips, did not want to reduce the pipes after running 2.5". I have a poor quality you tube clip so you can get an idea of the sound.



http://www.youtube.com/watch?v=fkQub...ure=plpp_video

MDchanic

Perhaps this thread will help you.

There is a thread running in which at least one person has expressed offense at posters being advised to use the Search function, but in this case, it might have been helpful.

- Eric

72w442

Better Picture



[IMG][/IMG]

507OLDS

I would run at least 2.5" all the way.If you have any future plans on upping the power on the engine,then I would put 3" on it now & be done.The size of the pipes don't really dictate the sound as much as the mufflers do.My 72 has 3" all the way,with DynoMax super turbos.It's pretty quiet at idle,and cruising,with a great sound when the power is on.A muffler like a Flowmaster is pretty much loud all the time,and you don't need a big pipe for that noise.

z11375ss

72w442, I can see a small speck of dirt on the top of your gas tank. You might want to take care of that. That car is VERY nice.
As far as the exhaust, not a big fan of 3" exhaust. Went with 2 1/2" and am happy with the sound. The x pipe is def not the way to go IMO. It sounds too Euroish if there is a word. The H pipe system creates a chambered sound. That, I like.

http://www.youtube.com/watch?v=Fcisq68X8Eg

Rickman48

I don't understand some peoples thought that bigger pipes make more noise!
The muffler regulates the 'sound' of an exhaust system - size has nothing to do with it!
Baffles, bends, and material regulate the sound from a muffler - the less restriction, the more noise and horsepower! [usually]
When freeing up a motor on the exhaust side, it's best to optimize the effiency [sp] by re-jetting the carb and re-curving the distributer.
What comes in must come out!
"X" and "H" pipes do about the same thing, the "X" being more efficient! Sound change depends on the muffler and position.

panos

Here is a good expaination about exhausts:

We've seen too much misinformation regarding exhaust theory. What kind of misinformation? For starters, there are a lot of people in the "Bigger is Better" camp. We're talking about exhaust pipe diameters. Even the big magazine editors are boldly smattering statements like, "For a turbo car, you can't get an exhaust pipe that's too big." Also, terms like "back pressure" and the statement, "An engine needs back pressure to run properly!" really rub us the wrong way.
Let's start from the beginning. What is an exhaust system? Silly question? Not hardly. Exhaust systems carry out several functions. Among them are: (1) Getting hot, noxious exhaust gasses from your engine to a place away from the engine compartment; (2) Significantly attenuating noise output from the engine; and (3) In the case of modern cars, reduce exhaust emissions.
Hardware

In order to give you a really good idea of what makes up an exhaust system, let's start with what exhaust gas travels through to get out of your car, as well as some terms and definitions:
After your air/fuel mixture (or nitrous/fuel mixture) burns, you will obviously have some leftovers consisting of a few unburned hydrocarbons (fuel), carbon monoxide, carbon dioxide, nitrogen oxides, sulfur dioxide, phosphorus, and the occasional molecule of a heavy metal, such as lead or molybdenum. These are all in gaseous form, and will be under a lot of pressure as the piston rushes them out of the cylinder and into the exhaust manifold or header. They will also be hotter 'n Hades. (After all, this was the explosion of an air/fuel mixture, right?) An exhaust manifold is usually made of cast iron, and its' primary purpose is to funnel several exhaust ports into one, so you don't need four exhaust pipes sticking out the back of your Civic.
Exhaust manifolds are usually pretty restrictive to the flow of exhaust gas, and thus waste a lot of power because your pistons have to push on the exhaust gasses pretty hard to get them out. So why does virtually every new automobile sold have exhaust manifolds? Because they are cheap to produce, and easy to install. Real cheap. Real easy. Like me.
"Ok," you ask, "so now what?" Ah, good thing you asked. The performance alternative to the exhaust manifold is a header. What's the difference? Where a manifold usually has several holes converging into a common chamber to route all your gasses, a header has precisely formed tubes that curve gently to join your exhaust ports to your exhaust pipe. How does this help? First of all, as with any fluid, exhaust gasses must be treated gently for maximum horsepower production. You don't want to just slam-bang exhaust gas from your engine into the exhaust system. No way, Jo-se'! Just as the body of your '94 Eclipse is beautiful, swoopy, and aerodynamic, so must be the inside of your exhaust system.
Secondly, a header can be "tuned" to slightly alter your engines' characteristics. We'll go in-depth into header tuning a little later.
Nextly, exhaust gasses exit from your manifold or header, travel through a bit of pipe, then end up in the catalytic converter, or "cat". The cat's main job is to help clean up some of the harmful chemicals from your exhaust gas so they don't end up in your lungs. In most cars, they also do a great job of quieting things down and giving any exhaust system a deeper, mellow tone. You'll see a lot of Self-Proclaimed Master Technicians (SPMT's) telling people that removing a cat will get you tons of power. There's room for debate on this, but in our experience, removing a catalytic converter from a new car won't gain you much in the horsepower department. It can also get you a $1500 fine if the EPA finds out! If you drive an OBD-II equipped car, you'll also get that damn annoying CHECK ENGINE light burnin' up your dashboard. (And for all you racers concerned with OBD-II's fabled "limp mode", you can put your fears to rest.)
From the catalytic converter, the exhaust gasses go through a bit more pipe and then into a muffler, or system consisting of several mufflers and/or resonators.
Are you a muff?

Exhaust gases leave the engine under extremely high pressure. If we allowed exhaust gasses escape to the atmosphere directly from the exhaust port, you can well imagine how loud and cop-attracting the noise would be. For the same reason gunshots are loud, engine exhaust is loud. Sure, it might be cool to drive around on the street with that testosterone producing, chest-thumping, 150 decibel roar coming from your car… for about 5.3 seconds. (Not 5.2 or 5.4 seconds… 5.3.) Even the gentleman's gentleman has gotta use a muffler, or system of mufflers, on their exhaust.
Again, you may hear a few SPMT's tell you that "Borla mufflers make horsepower!" Or "An engine needs some backpressure to run properly!" Nonsense. A muffler can no more "make" horsepower than Wile E. Coyote can catch roadrunners. Any technician with any dyno experience will tell you that the best mufflers are no mufflers at all!
Types of Muff

Mufflers can take care of the silencing chores by three major methods: Absorption, Restriction, and Reflection. Mufflers can use one method, or all three, to attenuate sound that is not so pleasing to the ears of the Highway Patrol.
The absorption method is probably the least effective at quelling engine roar, but the benefit is that "absorbers" are also best at letting exhaust gas through. Good examples of absorbers are the mufflers found in GReddy BL-series exhausts, DynoMax UltraFlow, and the good old-fashioned Cherry Bomb glasspack.
Absorption mufflers are also the simplest. All of the above named mufflers utilize a simple construction consisting of a perforated tube that goes through a can filled with a packing material, such as fiberglass or steel wool. This is similar to simply punching holes in your exhaust pipe, then wrapping it up with insulation. Neat, huh?
Another trick absorption mufflers use to kill off noise is, well, tricky. For example, the Hooker Aero Chamber muffler is a straight-through design, with a catch. Instead of a simple, perforated tube, there is a chamber inside the muffler that is much larger than the rest of the exhaust pipe. This design abates sound more efficiently than your standard straight-through because when the exhaust gasses enter this large chamber they slow down dramatically. This gives them more time to dwell in the sound insulation, and thus absorb more noise. The large chamber gently tapers back into the smaller size of your exhaust pipe, and the exhaust gasses are sent on their merry way to the tailpipe.
Restriction

Doesn't that word just make your skin crawl? It's right up there in the same league with words like "maim" and "rape".
Obviously, a restrictive muffler doesn't require much engineering expertise, and is almost always the least expensive to manufacture. Thus, we find restrictive mufflers on almost all OEM exhaust systems. We won't waste much time on the restrictive muffler except to say that if you got 'em, you might not want to flaunt 'em.

panos

The rest:

Reflection

Probably the most sophisticated type of muffler is the reflector. They often utilize absorption principles in conjunction with reflection to make the ultimate high-performance silencer. Remember any of your junior high school math? Specifically, that like numbers cancel each other when on a criss-cross? That's the same principal used by the reflective muffler. Sound is a wave. And when two like waves collide, they will "cancel" each other and leave nothing to call a corpse but a spot of low-grade heat.
There are numerous engineering tricks used in the reflective muffler. Hedman Hedders makes a muffler that looks a lot like a glasspack. In fact, it is a glasspack with a catch. The outer casing is sized just-so, so that high-pitched engine sound (what we deem "noise") is reflected back into the core of the muffler… where those sound waves meet their maker as they slam right into a torrent of more sound waves of like wavelength coming straight from the engine. And, this muffler is packed with a lot of fiberglass to help absorb any straggling noise that might be lagging behind.
The Exhaust Pulse

To gain a more complete understanding of how mufflers and headers do their job, we must be familiar with the dynamics of the exhaust pulse itself. Exhaust gas does not come out of the engine in one continuous stream. Since exhaust valves open and close, exhaust gas will flow, then stop, and then flow again as the exhaust valve opens. The more cylinders you have, the closer together these pulses run.
Keep in mind that for a "pulse" to move, the leading edge must be of a higher pressure than the surrounding atmosphere. The "body" of a pulse is very close to ambient pressure, and the tail end of the pulse is lower than ambient. It is so low, in fact, that it is almost a complete vacuum! The pressure differential is what keeps a pulse moving. A good Mr. Wizard experiment to illustrate this is a coffee can with the metal ends cut out and replaced with the plastic lids. Cut a hole in one of the lids, point it toward a lit candle and thump on the other plastic lid. What happens? The candle flame jumps, then blows out! The "jump" is caused by the high-pressure bow of the pulse we just created, and the candle goes out because the trailing portion of the pulse doesn't have enough oxygen-containing air to support combustion. Neat, huh?
Ok, now that we know that exhaust gas is actually a series of pulses, we can use this knowledge to propagate the forward-motion to the tailpipe. How? Ah, more of the engineering tricks we are so fond of come in to play here.
Just as Paula Abdul will tell you that opposites attract, the low pressure tail end of an exhaust pulse will most definitely attract the high-pressure bow of the following pulse, effectively "sucking" it along. This is what's so cool about a header. The runners on a header are specifically tuned to allow our exhaust pulses to "line up" and "suck" each other along! Whoa, bet you didn't know that! This brings up a few more issues, since engines rev at various speeds, the exhaust pulses don't always exactly line up. Thus, the reason for the Try-Y header, a 4-into-1 header, etc. Most Honda headers are tuned to make the most horsepower in high RPM ranges; usually 4,500 to 6,500 RPM. A good 4-into-1 header, such as the ones sold by Gude, are optimal for that high winding horsepower you've always dreamed of. What are exhaust manifolds and stock exhaust systems good for? Besides a really cheap boat anchor? If you think about it, you'll realize that since stock exhausts are so good at restricting that they'll actually ram the exhaust pulses together and actually make pretty darn good low-end torque! Something to keep in mind, though, is that even though an OEM exhaust may make gobs of low-end torque, they are not the most efficient setup overall, since your engine has to work so hard to expel those exhaust gasses. Also, a header does a pretty good job of additionally "sucking" more exhaust from your combustion chamber, so on the next intake stroke there's lots more fresh air to burn. Think of it this way: At 8,000 RPM, your Integra GS-R is making 280 pulses per second. There's a lot more to be gained by minimizing pumping losses as this busy time than optimizing torque production during the slow season.
General Rules of Thumb with Headers

You will undoubtedly see a variety of headers at your local speed shop. While you won't be able to determine the optimal power range of the headers by eyeballing them, you'll find that in general, the best high-revving horsepower can be had with headers utilizing larger diameter, shorter primary tubes. Headers with smaller, longer primaries will get you
slightly better fuel economy and better street driveability. With four cylinder engines, these are also usually of the Tri-Y design, such as the DC Sports and Lightspeed headers.
Do Mufflers "Make" Horsepower?

The answer, simply, is no. The most efficient mufflers can only employ the same scavenging effect as a header, to help slightly overcome the loss of efficiency introduced into the system as back pressure. But I have yet to see an engine that made more power with a muffler than an open header exhaust. "So," you ask, "what the hell is the best flowing muffler I can buy?"
According to the flowbench, two of the best flowing units you can buy are the Walker Dyno Max and the Cyclone Sonic. They even slightly out flow the straight through designs from HKS and GReddy BL series. Amongst the worst, are the Thrush Turbo and Flow Master mufflers. We'll flow some of the newer mufflers as they become available at our local Chief auto.
Resonators

On your typical cat-back exhaust system, you'll see a couple of bulges in the piping that are apparently mini-mufflers out to help the big muffler that hangs out back. These are called Helmholtz Resonators and are very similar to glasspacks. The main difference is that firstly, there is no sound-absorbing fiberglass or steel wool in a Resonator. And secondly, their main method of silencing is the reflective principle, not absorption. An easy way to tell the difference between a glasspack and a true Helmholtz Resonator is to "ping" one with your finger. A glasspack will make a dull thud, and a true Resonator will make a clear "ping!" sound.

Pipe Sizing

We've seen quiet a few "experienced" racers tell people that a bigger exhaust is a better exhaust. Hahaha… NOT.
As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route. Overlarge piping will also allow our exhaust pulses to achieve a higher level of entropy, which will take all of our header tuning and throw it out the window, as pulses will not have the same tendency to line up as they would in a smaller pipe. Coating the entire exhaust system with an insulative material, such as header wrap or a ceramic thermal barrier coating reduces this effect somewhat, but unless you have lots of cash burning a hole in your pocket, is probably not worth the expense on a street driven car.
Unfortunately, we know of no accurate way to calculate optimal exhaust pipe diameter. This is mainly due to the random nature of an exhaust system -- things like bends or kinks in the piping, temperature fluctuations, differences in muffler design, and the lot, make selecting a pipe diameter little more than a guessing game. For engines making 250 to 350 horsepower, the generally accepted pipe diameter is 3 to 3 � inches. Over that amount, you'd be best off going to 4 inches. If you have an engine making over 400 to 500 horsepower, you'd better be happy capping off the fun with a 4 inch exhaust. Ah, the drawbacks of horsepower. The best alternative here would probably be to just run open
exhaust!
Other Rules

A lot of the time, you'll hear someone talking about how much hotter the exhaust system on a turbo car gets than a naturally aspirated car. Well, if you are catching my drift so far, you'll know that this is a bunch of BS. The temperature of exhaust gas is controlled by air/fuel mixture, spark, and cam timing. Not the turbo hanging off the exhaust manifold.
When designing an exhaust system, turbocharged engines follow the same rules as naturally aspirated engines. About the only difference is that the turbo engine will require quite a bit less silencing.
Another thing to keep in mind is that, even though it would be really super cool to get a 4 inch, mandrel bent exhaust system installed under your car, keep in mind that all of that beautiful art work won't do you a bit of good if the piping is so big that it gets punctured as you drag it over a speed bump! A good example of this is the 3 inch, cat back system sold by Thermal Research and Development for the Talon/Laser/Eclipse cars. The piping is too big to follow the stock routing exactly, and instead of going up over the rear suspension control arms, it hangs down below the mechanicals, right there in reach of large rocks! So when designing your Ultimate Exhaust System, do be careful!

Rickman48

And that seemed like the opposite of the K.I.S.S. method, copied from a magazine!!
No offence - - -

66ninetyeightls

Pipe size may not effect the sound people hear outside the vehicle but an oversized exhaust sure as hell effects the noise (Droaning) heard inside the car.

panos

I never said that i wrote it my self now did i?

Rickman48

And those 'rice burners' with 1 1/2" in and 4" out - talk about drone - sounds like a pissed-off bumblebee in a tin can!!

Bunser

Just my humble opinion, 2 and 1/2 inches would be close to ideal.

z11375ss

Rckman48, I had a Cobra Mustang in 03. I but a bassani x pipe on it and it sounded like Euro trash. Very ricey as well. The H pipe may not increase effeciency any more than the H I agree, but it sure as hell sounds a lot better. I put the stocker back on it I hated that noise so much.

csouth

Eric,

Your insight is appreciated and I know how to use the search function. If you notice there is only one thing I have in common with the poster in that thread, we both have Olds motors. Before trying to make me feel stupid, you should notice I have a Big Block and headers, he as small block and manifolds. Thanks again for making me want to stay away from Classic Olds...

csouth

Thanks for the response. I was hoping someone could provide insight on that muffler. I think the Street Pro's ar the most tame of the mufflers they offer.

I may end up adding more power later, so 3" looks to be the smartest choice. Measure twice, cut once....

csouth

Panos,

Thanks for posting those facts, very helpful..

72w442

z11375ss Now thats a nice sounding exhaust, do you get a droan in the vehicle and are you using headers ?

How did you mount your camera for the ride?

Nice car

panos

no problem,glad i could help somehow. Now when i had the 455 in my 65 so i put a 2,5" magnaflow,i didnt think it was to loud inside the car,maybe it would be better with 3" and still resonable ,but i had some cheepo hedman hedders on it.
Here is a clip with quite good quality on the sound from inside the car.

http://www.youtube.com/watch?v=VhvY7...pBhSF2khsoW_Hc

507OLDS

The loudest,or most noticable part of the car,when the engine is running at idle,is the solid roller cam.I don't really here the exhaust sound,especially when I am in the car.

z11375ss

507Olds, that's damn funny. That must be really loud but a sold roller is a badass sound. 72, I don't get a drone in the car and yes, even with headers. Maybe because it's a 4 speed, as in the rpm is always changing. The camera is a Go Pro unit that suction cups to the car. It is strong enough that it can't be taken off the car unless you flip the clamp. I have a video of my Vette at zzz281996 on youtube. A couple other things too. Search for that and you'll find it. If you care.

csouth

Thanks for the sound clip. I think my real decision has is which muffler to use? Decisions, decisions

panos

like i said above,i like the magnaflows because they are nice and quite until you floor it

oldcutlass

I've got 2.5" out the back, heddman 1 7/8 primaries with dynaflow turbos, no H or X pipe, and definately no drone! I found over the years it all depends on the muffler on what kind of drone you get. I had a set of flowmasters on the Plymouth and it would resonate in the car at certain RPM's.

It also depends on your exhaust system routing, bends, and what they used to hang the system, on what kind of noise you will get in the car also.

70olds455

I think the street pros might be one of the loudest mufflers they offer at idle. They sound nice when you are driving and are not as loud as at idle. They also have a race pro muffler if you are looking for a performance muffler.

csouth

I actually think the Race Pro would be my choice. I checked their site and they say its the quietest they offer.

69'442

That's what I went with. Pypes 2 1/2 with the X and race pro's. Sounds good. Not too loud.

72hurst

x2

SBORule

I would install what fits best, Brian needs to post a picture of his car from behind like that other guy did that has that W27 cover so everyone can see how well his 3" inch exhaust hangs under there.

I replaced a 2 1/4" dual exhaust with Turbo mufflers on my Omega with 3" mandrel bent tubing into a Supreme Auto's 3"x3" X Pipe, that go into DynoMax Welded Race Magnums, I think they call them ultra flow's now. They look like a Turbo muffler but are sort of a straight through design, per say. I got the 3" offset inlet/center outlet with turn down just short of the rearend. Had it all welded together, so it's all one piece, I hate clamps.

The exhaust is off the car right now so I'll take a picture of my masterpiece and post it tomorrow.

Those changes alone allowed my car to run 2 tenths quicker and added 3 mph to my car's topend in the 1/4 mile over the exhaust system it replaced. This was back in 2000 and I raced the car in about the same weather and track conditions 2 weeks apart with no other changes other than the exhaust.

But the new exhaust doesn't hug the floor like the previous exhaust did and hangs pretty low, lower than I like, because of the floor in the car. If I was to cut that dip out in the floor behind the drivers seat where back seat passengers put their feet, I could raise the exhaust up a couple of inches and it would look alot better, atleast to me.

An X Pipe will make your exhaust note different for sure. At idle, you won't hear any difference really, I have been told a couple of times @ car hang outs by different people, that my car sounds better than anybody else's car and I hear cars that I wish my car sounded like, so it's all in the ear of the beholder.

Funny thing I experienced with the new exhaust was when I was running heads that had the exhaust cross over filled and the divider made flush on the center exhaust ports on the heads.

The car was louder @ idle and during acceleration and while @ cruising speeds without the heat crossover filled and divider flush. And the X pipe didn't have that FORD X Pipe sound during acceleration either.

When I put the high ported #6 heads on the engine, I could notice a major difference in the exhaust note @ idle, it was noticeably quieter yet made the engine sound somewhat more radical. During acceleration I noticed a major difference on the inside of the car, gave it more of an equal length header sound but during cruising speeds it was much quieter than it was with heads with open crossovers and divider not flush on the two center exhaust ports. It took a little getting use to but I have grown to like the new exhaust note on the inside of the car.

I have video of my car running 12.88 @ 103.5 mph after putting the ported #6 heads on, you wouldn't know there was an X pipe on the car going down the track, it sounded totally American to me. I will have to find that tape and post the video on my website here in the near future.

507OLDS

Yes,good point.My exhaust is tucked up VERY nice.The lowest point of the whole exhaust,is teh collector flange on the headers.It actually curves up after that,and fits in the cavities of the body,as it originally did.My exhaust is a 3" kit from Torque Tech,with H-pipe,DynoMax super turbos that are offset in/offset out,and the Torque Tech tails.There is always something that I don't like about a kit,so I hand-picked thse parts,just like everything else.It's never the cheap way.I think my whole exhaust,with Jet-Hot Hookers,all the way to the end,was every bit of $1100.00,by the time it got here.Torque Tech was one of the first companies making true 3" mandrel-bent systems for the GM A-body cars,and it is still one of the best fitting.They now offer some 3.5" kits,so I might do an upgrade when the 517 is installed,as I have a set of custom headers for that too.
The one thing I have grown to hate,is that all of the tailpipes offered,are just not quite long enough to come out through the 70-72 cutout bumper,and I don't like the look of a clamp & tip for everyone to see,so what I did with my existing tail pipes was I cut the ends off,right where they shot back to the bumper.I then had two 3" pipes made from polished stainless,about 22" long.The connection point where they are fastened with a clamp,is not visible,so all you see is a nice shiny tail.There are a few companies now,including Torque Tech & Ramairrestorations,that are making 2.5" and 3" trumpet tips,like the original 442 trumpets,so that is another product available now,that wasn't before.
You should also know that anything after the muffler can be reduced in size,if needed because the exhaust gasses have cooled,and need less pipe diamater to get out.I still went with 3" all the way,but if I do go up to 3.5",I will keep the 3" tails.

SBORule

Here's a pick of my 1 piece exhaust system.

xhuast.jpg

I'm hoping this system will be free flowing enough to handle twin 70mm turbo's someday, if not I'll have to add some electric operated cut outs in the system upstream and have that exit out the lower back corners of the front fenders just in front of the doors.

70Post

A 8 minute, something odd seconds reminder of why I don't watch TV.....WHO THE HECK NEEDS IT WHEN YOU CAN GET PROGRAMMING LIKE THIS!!!!!!!! THAT was FUN!!

Nice work, great sounds....heck, you could close your eyes, listen to the sounds and think you had "Bullitt" playing.

Great work and thanks. I knew that car looked good in your pic on your threads.....apparently sounds and runs as good as it looks.

z11375ss

Thank you very much.That flowmaster sound with the 4 speed is music to my ears as well. My exhaust is exactly what MY car needs. A full on race car or something with a bigger motor needs somethig entirely different. Hope I didn't state the obvious here.

442much

For me, since the size of my "X" and "W" manifolds are 2.25" so that's what I went with. Your exhaust is as good as its smallest diameter. If you're running 2.5" headers, then I'd go 2.5" max.

Also I didn't connect the right and left exhaust with a pipe. Joining the two sides will just synchronize and mellow out the sound. I like the sound I have now with my new Magnaflows. The original 442's with the 400 and 455 had 1-7/8" and 2" diameter pipes. So anything over that is an advantage.

csouth

My headers hav 3" collectors, so thats also a plus. Funny thing is I was talking to a local exhaust shop and the guy recommended h pipe over x pipe stating that the x pipe would kill my low end torque. He said because Olds motors are not generally pushed in the higher RPM's, that the x pipe would not benificial. Any thoughts?

ah64pilot

I am the last person to ever stand up for a magazine, as some of you may know...but as a turbo diesel tuner I would say that is a fairly accurate statement. The back pressure in a turbo system is provided by the turbo. While there is no additional performance advantage in having oversize exhaust in a turbo application, going to big will not hurt performance...and in most cases helps to keep egt's down.

SBORule

The guy doesn't know what he's talking about.

My headers have 3" inch collectors, my exhaust system is completely 3" inches in diameter, my car ran quicker and faster, tell that to the guy @ the exhaust shop.

Oh yeah, the new exhaust weighs more than the old exhaust did.

Scott Hamel

i am running 2 1/2 duals with flowmaster super 10s i'll post a video of the car running later today. its a 73 cutlass with a 68-69 toronado 455