[slobrd]

I've seen the articles that mention how good this type of cross pipe is, but I've also heard that they sound is very raspy. I realy hope this refers to their sound on other motors as compared to the big Pontiacs. Anyone heard these on a 455 3" system with headers?

[slobrd]

I've seen the articles that mention how good this type of cross pipe is, but I've also heard that they sound is very raspy. I realy hope this refers to their sound on other motors as compared to the big Pontiacs. Anyone heard these on a 455 3" system with headers?

[Jim Hand]

Slobrd,
For more info on the X crossover, and exhaust systems in general, go to Eric D's Pontiac Garage at address below: Jim Hand

http://www.wauknet.com/douthitt/

[Jerry Brock]

Slobrd,
I have a .030 over 455 with 2 1/2" exhaust and the Dr. Gas X pipe. With no other changes,changing from an H pipe, I gained 2 tenths and 2 mph. That was without even lifting the hood. i am running Walker Race Magnum mufflers, and it has a gereat sound. I had FlowMasters before and they had a 'tinny rattle' sound.

[slobrd]

Can you tell me more about the race magnums and the rest of the exhaust? I too am thinking about using these mufflers on a 74 bird because I'm tired of looking at big flowmasters hang under the car. They're also kinda common nowadays. I considered the flowmaster transverse muffler but it doesn't sound agressive enough.
Thanks

[Scott Horton]

I was considering one of these X-pipe crossovers. Reading the Dr. Gas literature, these things work by evening out the uneven firing order in each pipe (think of the V8 as two 4-cylinder engines, each with its own exhaust pipe, but not properly synchronized because they are joined by a 90-degree crankshaft). Unfortunately, it is exactly that uneven firing order that gives a V8 that distinctive popping growl. Dr. Gas' ad says that the X-crossover makes a V8 sound like a Japanese motorcycle. Now, I love the wail of a Jap motorcycle, but I don't want my GTO mistaken for one! I think I'll give up a little efficiency in my street GTO for that V8 exhaust growl I love.

[Mark Leischer]

I have hedman 1-3/4 headers, 3-inch collectors, next 3 inch cutout ( the kind you can buy in Summit ), through 3 inch Dr. X crossover, in to 2 Dyno max race bullet (cans ) mufflers, 3 inch over axle, into two 3 inch 2 chamber Flowmasters under the trunk floor ( fuel cell in trunk ). 455 Th400 3:73 rear ran 13:00-104 flat off the street (zero traction). Slicks and open cutouts 12.5--107. I love the sound from the Dr X crossover. Mark L

[slobrd]

Thanks for the comments Mark. What car is this in. I have honestly considered using a multiple muffler set up but the second gen F bodies don't have the room. I thought of running two race magnums and a transverse muffler. It may be overkill but this is the one area of the car I've reserved for an uncommon approach.
I'm sure interested in your comments on your car's sound during normal driving if it is driven on the street.

[Tim David]

I reciently put a set of Ram Air Reproduction
Manifolds on my 79 Trans Am. Does anybody
know of an X or H pipe that will bolt on to
the manifolds?

[Michael Farich]

Have one week of driving time with a new 2.5 inch "X" on the mild 400 Pontiac daily driver. New set of Dynomax 17749 Hemi Super Turbo's and 2.5 inch pipe all the way except for short pieces of 2 inch at the manifold outlets. I like it for a daily driver. It's quieter out on the road and at WOT. Still sounds plenty throaty at idle and just off-idle cruising around in the parking lot at work in the morning. When the rpm's go up the exhaust seems alot smoother and quieter than the old system. The induction roar of the Q-Jet is more noticeable even with a closed element air cleaner. It's hard to tell with such a mild 400 but there might be a slight increase in torque at WOT above 3500rpm. The real intent of this system was to make the car a little quieter and to increase exhaust system capacity for about a 325hp 462 Pontiac motor someday. (The old system was 2.25 all the way back with small case turbo mufflers.)

[Gach]

I have the Dr. Gas x pipe 3" system on my 70 455, with their muffers. I was very disapointed, their claim was the car would run as fast as open headers, WORNG! not even close. It's ok for idleing around untill you put your foot into it. then it sounds just like open headers. The car can be heard for
blocks

[old gto]

On my `66 driver I`ve got 2&1/2" pipes with an X in them, running cherry bombs (anybody remember them?). No fancy doctor anything, these were done at a local muffler shop from the stock manifolds to the rear for under $200. They sound very good, (certainly not like any rice burner I`ve ever heard!). I`ve never run the flowmasters, are they worth looking into.......and why?

[Tilster]

I've got a '70' 400 with 2.5 aluminum and three stage Flowmasters. Sounds nice for stock engine. I had two stage Flowmasters for a day and found it to be to loud for daily commute. Convertible hardware rattled.
But there sure was a greater response and hp with the two stage from stock mufflers. And there was a noticeable difference between three stage vs. two stage, two gave more power.
This was very clear for me to recognize since I had ran with stock mufflers for 17 years. I am sure others will have more input on different brands and post.
I like mine for now but will change when tired. Look into a type that gives the performance and sound that you want. My Flowmaster three chamber's sound deep with a hint of tin.
Tilster

[old gto]

One thing I noticed with the X is the back pressure is not there......I remember the cherry bombs "popping" when you let off the throttle, but these are fairly smooth, even with the mild cam. When I was a kid, everybody had either thrush hush or cherry bombs. My car looks like it`s the early 70`s.........chrome reverse w/baby moons, rear up on hi-jackers....ahhh the good `ol days!

[T Hutchinson]

The X crossover both quieted and very slightly increased seat of the pants accelleration on a friends 70' GTO (400 ci, 280 cfm d-ports, 248 duration 580 lift solid cam, 1 3/4 headers, 3" exhaust out the back, Super Turbos)The sound is definently different... less rumbly??? Like an old gas dragster with the short pipes comming off each exhaust port, much quieter of course.

[Tom Hand]

Lou, interesting results from your testing. Were you able to do all this testing at the same track on the same day? Did your weather conditions change or were you able to measure it throughout your testing? Can you tell me what mufflers and exhaust system you used before? Was the engine making 300, 400, 500, 600 HP? What size headers were they and what size crossover did you install? Were the pipes the same diameter all the way out to the rear of the chassis or did you neck them down? Can you email a photo to me so I can see where you located the junction? I like to keep these on file so that when people ask how far the junction has to be past the cross member, I can show them what others have done. What part number mufflers did you use? Thanks,
Tom Hand

[David Holmberg]

Tom, As little as those nascar boy's know about horsepower, Yates, Hendrick, ect, I guess they have X and H crossovers on their cars by accident...maybe just for added weight?

[Gach]

I've competed in some close exhaust competition, and was looking for the best exhaust system. In talking to Mr Gas, I was told the X pipe system would produce more hp then open headers, NOT TRUE!! I ran their whole exhaust system, their ( Wave Trap mufflers ) The system I first bought was
their 3" X pipe cross over..... into their 3" mufflers, and 3" out..... into 3" tail pipes. What a joke, you don't need to do much testing, it's simple, you make a run with the exhaust system on, then take it off. My car slowed down 5 Tenths with their system. When I call them they said oh, you need 3½" because your collectors are 3½, your reducing them to 3" an it's killing your torque, well then, why did they sell me the 3" X over pipe system then ? I went on what they recomended. Ok", so now I buy their 3½ X pipe set up, not cheap buy the way.


After reduing my whole exhaust system ( big dollars ) I made another trip to the track, guess what ? I still went 4 tenths faster with open exhaust. I call them again, ( get this, this time, the guy tells me himself that the Walker mufflers are actually better then there's ) each time the exhaust system was installed exactly to their spec.'s. the cross over was place exactly were they told me to install it. After talking to the guys who run Heads up classes ( which closed exhaust is a must ) this is what I ended up doing, I now run 3½" pipe into 3½" Walker Mufflers with " NO CROSS OVER" the same
mufflers they said were better then theirs, the car now runs the same with open headers, as with closed exhaust, no slower or faster.....go figure, and for haft the price.

David, racing NASCAR, and drag racing are two different things, the biggest market is Pro Street,and all those closed exhaust Heads Up Classes, if their system was what the said it was, they'd all have them on their cars, don't be suck in .

Tom, I know your a big seller of their systems, and your mainly looking for what's the quietest system out there for the street, you've even offer to sponsor me with one of their systems. I think it was a great offer. So if anyone wants to inpley that I'm just bad mouthing their system I got news for you,
I'll take anything that's for free, but not if it's going to slow my car down!.

I'm not telling anyone not to run their systems, but I have many guys who have installed their systems under the impression they would run as fast as open headers, not one ever did, now if you don't care about running as fast as open headers go buy their system. One more thing this Walker set up I
have on the car now is actually quieter.... go figure.



[This message has been edited by Gach (edited 06-17-2000).]

[Tom Hand]

Lou,
I do need to correct you in that I am not a "seller of anybody's parts". I work for Honeywell and have no part in any business. The benefit of this forum is that with all the facts, others can make educated selection of components.
Luckily, I have had the good fortune of being able to ask some manufacturers if they could help many folks, like yourself, willing to test things to help all find out what works and what doesn't. I am glad so many are willing to do so.
I hope you can address the questions I asked previously. What part number muffler did you have from them? They make several (as far as the catalog they just sent to me shows) and it looks as if some are vastly different. Which Walker muffler ended up being the best? Walker makes many and it good to see that you found some that are quiet enough to run. After your controlled testing, you did take into account that the weight by itself contributes to a reduction in MPH and an increase in the ET?" I imagine yours should have weighed at least 90 pounds. Is this pretty close? Can you share what power the engine has and also share some of the other contributing factors that affect the way it reacts with open vs. closed exhaust? Is it 300, 400, 500, or 600 HP? All these things matter for people that want to duplicate the system. Exhaust, like any other modification, (heads, cams, carbs, etc) are related to and affected by many other things. Unfortunately, your car did not act like most I have seen, read about, and seen tested. That is the way things go sometime. Thanks for providing the information. Can you still email the photos to me (thand@sprintmail.com)?
Tom Hand

[Tom Hand]

Slobird,
To offer another answer to your original question, the X tends to smooth out the sound. In my opinion, it makes Pontiacs sound less like Pontiac/Buick/Old engines and more like higher winding Chevrolets. In every case we have used or seen one being used, they tended to get rid of the raspiness and choppiness and mellow the sound. Even on cars with Flowmasters that were sort of crackly, the X tended to make the sound less so. Many factors will control the sound, like compression and camshaft timing, etc., but mufflers will have a big impact. What sort of mufflers were you thinking about? We have many that have been tested over the last few years and maybe I can tell you which will do what. You are most welcome to borrow anything I might have that will fit or I can research the ones you are thinking about and see what others have experienced.
Tom Hand