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Question about crossover pipes on dual exhaust

Discussion in 'The Hokey Ass Message Board' started by Frank, Jan 5, 2006.

  1. Frank
    Joined: Jul 30, 2004
    Posts: 2,325

    Frank
    Member

    Just had duals put on my 66 Galaxie 352 4brl. No crossover pipe was put in. How important is a crossover pipe? Does it improve performance?

    WHat is the best method to determine where the pipe should go? I have heard of guys painting a white stripe from the headers back on the underside of the pipe. Drive it until it burns off then look to see where the paint stopped burning. This is the spot to put the H pipe. Anyone ever tried this or is it an old wives tale?

    I did a search first but didn't find the question ever covered.
     
  2. lakes modified
    Joined: Dec 2, 2001
    Posts: 1,283

    lakes modified
    Member Emeritus

    That's a great question that i would like to know also.
     
  3. dadseh
    Joined: May 13, 2001
    Posts: 526

    dadseh
    Member

    So you want the factory sound.....
    Automakers and performance enthusiasts have been installing balance tubes in dual exhaust systems for years. Tests have shown that balancing the backpressure between the independent exhaust branches increases power and reduces resonance. When Chevrolet introduced the C5 Corvette it installed a simple "H"-pipe balance tube. It was roughly two inches in diameter and provided adequate flow between the 2 1/2-inch catalytic converter pipes.
    Factory System
    For reasons unknown, a running change was made to the "H"-pipe sometime in model year '97. The change resulted in using a smaller connecting passage of approximately 5/8-inches, thus rendering the "H"-pipe ineffective. From that change forward, C5s have had the smaller balance connection that contributes to a popping exhaust sound on deceleration and a gurgling, or "motorboat" sound at idle.
     
  4. socal_wrench
    Joined: Mar 3, 2001
    Posts: 258

    socal_wrench
    Member

    I like a crossover pipe after the front u-joint, has a dual purpose.
    I Always use 1.5 or larger pipe.
     

  5. chuckspeed
    Joined: Sep 13, 2005
    Posts: 1,643

    chuckspeed
    Member

    The closer the h-pipe is to the exhaust ports - the better the effect of the connection.

    Ideally - the H pipe should be same diameter at the exhaust pipe for maximum effect.
     
  6. sojerscraper
    Joined: Nov 12, 2005
    Posts: 214

    sojerscraper
    Member

    im running 2" pipe, straight off each manifold, glasspacks up front under the front seats, no balance pipe on a slightly modded 383 mopar. i never get any popping but it does have a pretty loud rap, which was what i was shooting for. as far as performance vs my old system that was 2.5" with flowmasters and a balance tube: the current setup seems to produce more torque off the line since it has more low end backpressure but it lost a little up in the high end, my guess because of the restriction - but goddamn does it sound f'n good! i love when im at the gas station & theres people walking up to the mini mart, when i fire it up they jump, turn around & smile. good stuff.
     
  7. El_Hefe
    Joined: Jan 7, 2008
    Posts: 1

    El_Hefe
    Member

    I just got a 2 1/2" dual setup on my truck. i picked it up late after work, and when i looked under the next morning, there was no balance pipe. i called the shop, and the owner said he forgot to tell me. the white paint deal is tried and true, and he said there will be a burn on each pipe after a few days of haulin' ass, and this spot is the sweet spot for pressure. then you put in the pipe. he said any other spot is a waste of time, since the pressure and heat which you are trying to address is focused there, and no one can guess where that is.
    i am swapping my 327 for a 400 soon, and he told me i should relocate the pipe after, since the 400 will have a new sweet spot. he said running convertors or not moves that spot as well. just guessing for the best look or easiest fit is a waste of time. fascinating...
     
  8. Dadseh covered it quite well.

    My understanding is that not much is gained in the HP department, 2-4 HP or so, but anytime you get 'free' HP....

    Size on the street doesn't make too much difference.
    I run 2 1/4" on a 2 1/2" system which makes for a little easier install.

    The H-pipe is not in the proper - advantageous for HP gain - place either.
    A matter of convenience since the underside of my 32 is crowded where the pipe should have went.

    Doesn't really matter since I can only run small mufflers - glasspacks, Turbo's, 2 chamber FlowMasters etc. - and sound attenuation was the goal.
    It did quiet things down and took the low frequency rumble out of it.
    Doesn't seem to bother as many car alarms in the parking garage that it used to.

    Definitely make a point to install a flange - or two - for splitting the system.
    I didn't because the whole exhaust system comes out after the six collector bolts and four support bolts are removed.
    Even so, there's been a couple of times I wished I woulda had a flange.

    Dual flanges would help in the transmission removal dept although I think the T-400 in my 32 would come out ok as is.

    [​IMG]
     
  9. GassersGarage
    Joined: Jul 1, 2007
    Posts: 4,727

    GassersGarage
    Member

    Unless you want that last bit of power, I wouldn't bother. For me, it's just easier from a maintenance standpoint, not to have to drop the crossover. If I decided to run my car at the track, I would just uncock it anyway.

    There's also the X-pipe configuration.............
     
  10. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,408

    atomickustom
    Member

    I just added one to the 2 1/4 dual exhaust on my '53 Chevy (with a 350 in it) and turbo flow mufflers. It made a huge difference in how loud the exhuast noise is inside the car - at idle it's now very quiet and only resonates in a pretty specific RPM range. If you want a racy, rough sound don't add it. If you want a smooooth, quieter sound, do add it. I doubt the performance difference will be detectable in the real world, but the sound difference is night and day.
     
  11. 50Fraud
    Joined: May 6, 2001
    Posts: 9,907

    50Fraud
    Member

    This was also my experience. I had a non-crossover system in my '36 (flathead with Flowmaster Hushpowers) and it had what I thought was an obnoxious rap. Adding a crossover smoothed out the rap, and I thought improved the tone greatly. If there was any performance gain, it was minor.
     
  12. 1931S/X
    Joined: Apr 5, 2007
    Posts: 667

    1931S/X
    Member
    from nj

    if you want a real simple way to split your h pipe, just cit the pipe i nth ecenter and install a stainless steel band clamp. done deal. no leaky flanges or slip fits that dont exactly slip. i like an H pipe at the least. im a big fan of an x pipe, they give a pretty wicked sound at higher rpm and are real easy to make. if it adds power and helps scavenging, great. youll never feel 4hp. if you are builing an exhuast its jus ta few mor eminutes of work, well worth it.
     
  13. Hanksville Hot Rods
    Joined: Oct 23, 2006
    Posts: 247

    Hanksville Hot Rods
    Alliance Vendor
    from Denver-ish

    Band clamps are definitely the way to go; they also work great for attaching the tailpipes to the mufflers to make it easier to r/r the tailpipes

    I agree that for the relative cost, it's worth it to add some sort of crossover to help tone down the sound and, like 1931S/X said, if it adds power, that's great too. Most of our customers opt for the H-pipe but some go for the X. We use the same size tube for the crossover as the rest of the exhaust.

    Hank
     

    Attached Files:

  14. Like the previous comments, I have the crossover on a 390 powered Caliente. It mellowed down the sound and made the turbos sound great. I don't have a crossover on my 396 powered Cameo, and using the same mufflers, it is noticeably louder.
    Bob
     
  15. parksquijada
    Joined: Aug 6, 2008
    Posts: 316

    parksquijada
    Member
    from norcal

    this guy has it right

    also:a cross pipe eqalizes the exhaust pressure between the two pipes but more importantly lets each bank of cyls use the volume of both pipes/mufflers. do it.

    the paint on the pipe idea is bs but does work for length on race pipes.
     
  16. Once again some fact and a lot of nonsense. The 'H' pipe will smooth out the sound a bit while adding some mid range torque. An 'H' will reduce the "rap" and "Braapp" noticeably. Size wise, hours of Dyno testing has shown me that diameter equal to the primary header tubes or about 3/4 the size of the exhaust pipes works best.
    X Pipes add a bit more power and are done from the same size pipe as the rest of the exhaust system.
    As for the paint deal to figure out where to put an 'H' pipe doesn't really work. Paint on Collector lengths of drag cars will give a good indication of where optimum length will be for that particular car and motor setup, but for 'H' pipe location there are way too many variables for this to mean anything. Put it fairly close to the collectors and call it good.
    The reality is for most of the cars here - it's more about sound changes than power.
     
    dan31 likes this.

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