New pipes are next: Any opinions?

[X33RS]

I don't know if this will answer your question Gary but I do know that the "H" or "X" setups are most effective close to the engine 12"-18" back.  Has something to do with the hotter exhaust gasses that are moving quickly vs the exhaust gasses having more time to cool as it travels towards the rear.
  That's also the reason why running smaller tail pipes (smaller than the rest of the system) has no measurable affect on HP output.  By the time the exhaust reaches the tailpipes it's cooled and traveling slower.

   There are transverse mufflers on the market that actually have an "X" design inside the muffler.  Dynomax makes one that I know of.   But that theory I stated above makes me wonder how effective it would be.

The Dynomax transverse system I bought here...   http://www.jegs.com/i/Dynomax/289/89021/10002/-1 

Uses a super turbo Dynomax muffler design which is their quietest, but flows more cfm than the stock Z28 deep tone muffler and as a result I think is slightly louder than a stock system (plus the pipes are bigger too so that affects sound).  However if you want more, you can substitute this muffler with a couple of different Dynomax tranverse mufflers like the ultraflow or the welded case "X" design.   Each one will have a different sound I'm sure.  But for only $260 for the system with the turbo muffler you can afford to experiment a little if someone wants to. 

[69Z28-RS]

I think you are right about all that Larry...   the closer to the engine, the more effective it is... although I think it would be effective wherever it is located (to varying degrees).  I'm fairly certain that the stock transverse muffler shares a resonant chamber between the two ports, although I haven't seen one cut apart...  I don't see much reason to have two pipes sharing one muffler housing unless that were true.

PS.  I've always thought that turbo mufflers provide a great sound... 

[X33RS]

I went this route with the stockish turbo muffler in hopes that my wife approves.

She is fine with the Pypes transverse systems I've used, they are actually rather quiet inside the car with no drone at all, so I suspect this Dynomax turbo muffler should be similar if not maybe a tad quieter.

If it passes the wife test I may pull the muffler and install the dynomax ultraflow for a little sound comparison.  If I get in trouble I can always switch back.

I just didn't go with the Pypes on the Z this time around (even though it's a wife safe system) because I really feel the need to run factory reproduction tail pipes.  Can't do that on the Pypes system.   If you have ever seen the muffler design on that system it's rather unique.  It's a transverse "race pro" with one side having the inlet coming in the top on one side and exiting the bottom on the other side.   On the other side the inlet is on the bottom and the outlet comes out the top on the other side.  Making the tailpipes specific for the application.  This particular cross flow muffler has a straight through design (same pipe enters and exits the muffler case) hence the reason for the opposite enter and exit locations on the muffler.

 Fitment has always been excellent, I like the stainless construction, the "X" pipe, and most important the sound level is great with no resonance inside the car.

[69Z28-RS]

I wonder if any of the 'X/H pipe fans' know that Chevrolet actually designed/installed an 'H pipe' on the factory stock dual exhaust '57 Chevrolets???   It was VERY close to the engine, actually connecting the two exhaust pipes right out of the manifolds and the connector pipe running around the front of the engine...  For some reason, I think that '57 was the only Chevy (I'm aware of) that did this from the factory.

[Z10Mike]

The C1 Vettes with dual quad and FI systems had the dual exhaust cross over pipe at the front of the oil pan.  My '60 270hp job was set up that way.  It ran strong and had a unique tone.  Miss that car.

[X33RS]

Yep, even Ford has been doing it for decades on all their performance stuff.  My 69 SCJ has a factory "H" pipe.  Even my sons 89 5.0 mustang has a factory "H" pipe in between the 4 cats they put on it, so I don't think Ford ever stopped the practice.    The last customer mustang I worked on was a 65 289 and it also had a factory "H" exhaust on it so I know it at least goes back that far with Ford.

[KurtS]

IIRC, the X-pipe gain has to do with scavenging efficiencies. The charge coming down one pipe helps scavenge the other pipe.
Been a while since I read about these systems, YMMV.

[cook_dw]

IIRC, the X-pipe gain has to do with scavenging efficiencies. The charge coming down one pipe helps scavenge the other pipe.
Been a while since I read about these systems, YMMV.

Correct.  It also allows a smoother transition between the banks and helps draw exhaust from one side to the other (i.e. scavenging).  X-pipe over H but either is better than none.

Quick read.

http://www.superchevy.com/how-to/exhaust/1504-x-and-h-pipes-add-easy-horsepower-but-which-is-best-for-your-ride/