or maybe H? :rolleyes: what would you recommend for my exhaust? it will be a 2.5" dual flowmaster(2 chamber high flow) setup starting at the hooker supercomp headers 1.75" and dumping behind the rearend. should i X or H it and why. and what do you think about the 2 chamber mufflers? i want that growling throaty sound,aggressive but not obnoxious? give me some input so i can get it done. graemlins/thumbsup.gif
Zack68

I prefer the X anyday. If for no other reason than the sound. It sounds a ton better with the X. And seems to have more response and torque, but have never done a back to back comparison. I used to only run Flowmaster muffs. A friend talked me into Dynomax Ultras, and I ain't never looked back.

most people on my late model mustang forum say that an x combined with chambered muffs sounds bad. I have an x on my 01 cobra with some magnaflow straigh through mufflers and i dont really like the way it sounds. I may up grade to chabmered muffs soon.

Don't make the mistake of using a collector reducer. Maintain the collector diameter all the way through the x-pipe then reduce it down.

The x showed a little more hp and torqe then the H but, you can't always get an x on all cars where an H allows a little more room.

I installed a DR.GAS X-PIPE in my 68 into Flowmasters exits in stock location.I called them &they recommended system based on my H.P. Was a little more work to install but well worth it.Love the sound & performance.

the idea is too equalize pressure and cancel some pulses (I'm not all up on the science of it)
but it works

X is supposed to be a little better
H is working fine for a lot of folks
X is more expensive
as was mentioned space constraints
but either should fit a properly designed exhaust under any gen of camaro

those flow will drive you crazy if you don't cross them over. i've had them both ways with a similar exhaust and was much more tolerable after Xover

Here is some specific information on this subject:

The X discussion (http://www.camaros.net/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=4;t=006224)

http://www.pontiacstreetperformance.com/psp/exhaust.html

The 3rd page of this discusses H vs. X.

Zack. I went through the same thing and contemplated a the same options with many, many, many different people. Basically what I found was this. To get the true benefits or fullest potential of an "X" pipe your HP should be near or above 400. I do not know how true this really is but I have heard this from reputable sources.
I insatlled my X in my 355 and this is my build:
355 block
AFR 195cc heads
10.325:1 compression
1.6 roller rockers
XE274 comp cam
RPM Air gap
Holley 650dp
Hooke 1 3/4" super comps.

I went from 2.25" straight pipes that went into 40 series flowmasters and I Changed this set up to the DR Gas X pipe. I am running a 3"pipe prom the collectors into the X and 2.5" out of the X to 40 series flowmasters.

I definetely noticed a difference in my low end. I love the sound of the flows with the X pipe. At idle she has a nice sound to her but not too loud. When I get on it she roars real nice.

I would recomend the X pipe if you willing to spend a little more.

Also, the positioning of the "X" is critical to where your torque curve with end up.

I've got a 3" X on mine and love it, has a great sound

hey guys thanks for all the info. i've been looking into all the info. my engine should be around 375-400hp. some people tell me small blocks around 400 hp like a little back pressure and 3" pipe is to big. is this true? i think i will definitely go with an X pipe. reading the previous posts there is different points of view as to whether the X itself should be the same size as the collectors(3") or same size as the rest of the system(2.5") i'd like some more input on this. also does anyone have an actual pic(undercarriage) of a "true" X pipe and a not so true X setup?
thanks,
Zack 68

Originally posted by zack 68:
some people tell me small blocks around 400 hp like a little back pressure They do huh? - you should stop talkin to them immediately! graemlins/clonk.gif

The backpressure bit cracks me up every time I hear it - I always say
"man those 4"pipes must be killin my ride" They need to read some of David Vizards
exhaust articles if they still believe that backpressure garbage.

Anyway, definitely try to run 3" to the X, from there 2 1/2" will be fine for a 400hp engine.
The X works kinda like a plenum - it allows more volume in the system, the pulse from
one 3" pipe sees dual 2 1/2" pipes, plus exhaust gasses cool off farther down the system
anyway. A 3" collector is actually too big for most street small blocks, but thats what
most header manufacturers push. Ideally you'd want a nice merge collector around 2 1/2"
in dia. right as the primary tubes come together, then go right up to 3" dia. of about 18"lg,
this would make for good scavenging.

Unless you are willing to cut off the collector and rebuild, you should use 3" to the X. With your 30" SuperComps, the first area change in the X (the leading edge of the intersection) should be about 19.5" from the ends of the primary pipes. A little longer than that would be acceptable, but beyond 21" you would start to lose some midrange and top-end.

The overall length of your header from the back of the exhaust valve to the intersection in the X-pipe should be about 50". Since your collector is over a size too large, you need to add some length to restore the proper wave timing - thus 52" total.

Positioning the X is key.

It you go into the Dr. Gas website they have a picture of a 1st gen camaro

I just gotta second 67RS502's comments. I undoubtly agree.

I will add this as well.....why dont you call the guy who designed the "X" in the first place.....as he is one who designed the 'Dr. Gas' effort and sold them the rights? Anyway, he has more emperical data on this design than everyone else combined. Considering, that the "X" designs didnt hit the 'scene' until about 96 or so? OK, well I have had the original design on my 67 since 1989 and I love to hear how most come up with their ideas and theory on what really takes place in an exhaust system.....without any 'instrumented' data.

I dont really get this whole 'position' thing either. It really isnt relivent in an "X" system. It is however, paramount in "H" type systems though, but that is not the topic here.

I must also point out something that has been stated by Nova, that needs to followed to a "T":

Maintain the collector diameter all the way through the x-pipe then reduce it down.
I would like to add that IMO, that it should maintain the diameter to the muffler inlet and be reduced (if at all) post the muffler itself.

Zack, I'll try and get a few pictures of the exhaust on the 67 posted sometime soon as I havent the slighest idea where the fabrication pictures have been placed or misplaced somewhere in the last 15 years. It is really hard to visualize what is being talked about without somekind of reference.

graemlins/thumbsup.gif

ok. so are you saying that if i have 3" collectors that i should keep it 3" through the X to the muffler and reduce it to 2.5" out of the muffler through the rest of the system? graemlins/clonk.gif i want to do it right the first time so please correct me if i'm wrong.
zack68

Yes. If I were to do the system your are considering, I would use 3" to and thru, with a 2.5" tailpipe....there is also an option for a 3" tailpipe, but not necessary with what you are trying to accomplish at the noted power level.

All of the systems that I have done and know about that have been tested, to include chassis dyno and specific instrumentation, have shown good things in all directions when the system has been constructed with the same diameter tubing from the collector, thru the "X", to the inlet of the muffler. I have even used the same diameter aft of the muffler, but only in super or turbocharged applications because of volumetric requirements and some other related velocity issues. The instrumentation provided information about the pressures and temperatures in sections of the exhaust system. This is what steered us into the direction of the final product, concerning the 'true' "X" system on my 67.

Other than that, in a street RPM bandwidth, the use of a smaller muffler outlet tubing diameter showed to provide a slight increase in torque where it would make sense for a street car. I am not saying it is a huge number, but every little bit helps in a street RPM bandwidth.

FYI I like to run 3.5" to and thru, with a 3" tailpipe on large CID or healthy big blocks. I like to use 3" to and thru, with a 2.75" or a 2.5" tailpipe.....or 2.5" with a 2.25" tailpipe depending on power levels achieved. The 2.75" stuff gets kinda expensive because it is an 'off' size for exhaust tubing, but it too has its place in certain applications.

3" with 2.5" tails.... sounds good to me graemlins/thumbsup.gif

thanks chicayne. this is what it will be since i have an appointment tommorow morning at the muffler shop to get it done.
graemlins/thumbsup.gif zack68

Originally posted by zack 68:
thanks chicane67. this is what it will be since i have an appointment tommorow morning at the muffler shop to get it done.
graemlins/thumbsup.gif zack68

Chicane, are you running the Thorley headers? I ask because don't they have 2.5" collectors and, if so, how have you merged into a 3" X-pipe system? I'm interested as I am looking at the Thorley/Doug's headers. Thanks.

I am running the Dr Gas X pipe setup and love it. I called them and talked to them prior to buying and told them my engine/gear setup. They said, for best results, running 3" from the collector to the X is best, then 2 1/2 back to the muffler, unless you are running 600 hp or more. They also told me that you can run 3" all the way, but it does nothing for performance, only costs more.

I am running just a bit over 500 hp, and have the 3">X and 2 1/2> muffler setup like they suggested. It not only pulls much harder, but sounds super. My son is running DynoMax ultras on his and the combo sounds very powerful.

I am running the 2.5" x-pipe from Pypes with ultra flows. I went from an h pipe with old style 2 chambers. The resonance has virtually been eliminated and I can feel a differnce in power. The only time I miss the old Flowmaster sound is when I pull into a parking lot at a cruise. My car idles fairly quit but sound great when I get on it....
I'll try to take some pictures when I get a chance and maybe even a sound bite..

Yo Rick, whats goin on Homie? Yea the current exhaust system I am running employs Thorleys....and yes they do have a 2.5" collector. I am not however, running an "X" pipe to the likes of anyone else. The true "X" system used in this build has 2.5" tubing from the collectors, to and thru a 'True X' pipe and then it is reduced down to 2.25" aft of the muffler (a 15 yearold set of custom, 3 chambered Race FlowMasters). The "X" pipe that most of you are running and/or have seen, is a much more simple approach, but doesnt quite do what the true "X" system actually does. It basically goes a few steps beyond, but is much more costly and difficult to configure and fit into a chassis.....not to mention there is a weight factor.

Take a look at the page I whittled up to kinda give you an idea on how my current system is constructed. This is how I do my own and what I do for my 'maximum effort' builds for my customers:

The exhaust page (http://www.geocities.com/tholt67/exhaustsystem.html)

I wish I could believe what 'Dr. Gas' has to say about what to run with certain power levels...... since they are not and were not the ones that did the actual instrumentation and testing of the design, that they now market with their name on it, it is mearly a gross recommendation. Which will suit most people, but you can dig a little more....and get a lot more out of it in the end.

Afterall, using the same diameter all the way to the muffler.....does change the intermediate volume.....which does effectively change the associated pressures before the muffler. That just happends to be where you get the biggest gain out of this type of system. But, then again, you are talking about the simplified "X" system. Your not gonna get much more out of that design.

[ 04-13-2004, 05:04 PM: Message edited by: chicane67 ]

I have been told that an X wouldn't be of much value on a convertible because the X brace forces the location of the X pipe too far "downstream". Is that correct?

Well, if anything else.....it is darn hard to fit one because of the brace....that much is true. But as far as being too far down stream, you can not really put an 'X' into the system aft of the tailshaft to begin with.

I have the Dr Gas system on my vert. I also don't have the X-brace due to my rollcage and welded SFC's. Having said that, it's fun to try and tuck the system up but it can be done. Of course, not as tightly as a coupe.

Originally posted by RickD:
Chicane, are you running the Thorley headers? I ask because don't they have 2.5" collectors and, if so, how have you merged into a 3" X-pipe system? I'm interested as I am looking at the Thorley/Doug's headers. Thanks. FYI, There are Thorley Headers and there are Doug's Headers. Doug's Headers is run by Doug Thorley and his product line is much more complete than the Thorley header line. Also, I have read nothing but good about the quality and fit. Apparently Doug Thorley sold the rights to his own name to Jardine but he has started a whole new company with the name Doug's Headers.

Tommy G, I am just wondering if you have dyno'd that motor of yours? What kind of hp/tq numbers are you getting? Thanks.