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Bad ass pipes

Discussion in 'Norton Commando Motorcycles (Classic)' started by jseng1, Jul 6, 2018.

  1. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    Herb Becker made these pipes for Andy Cox's unstreamlined land speed racer (149mph so far).

    "...start out at 1 5/8", then steps to 1 3/4", then 1 7/8", then finishes at 2", with reverse cones. We were pretty happy with the results; ... 94rwhp.
    [​IMG]

    [​IMG]
     
  2. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    I saw a guy at the Broadford Bonanza about 3 years ago with a commando with pipes like that. With a commando motor, it is big enough to still have power if it drops off the megaphone on a road race circuit. But I would not like it. For a land speed record, it is probably OK if you stagger off at the beginning and get a big kick in the pants as the motor comes on song.
     
    MexicoMike likes this.
  3. Jerry Doe

    Jerry Doe Admin

    Joined:
    May 21, 2003
    I bet that sounds great. Any movies anywhere?
     
  4. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    I'm loving those pipes
     
  5. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    You might be able to hear them at Bonneville this year.
     
  6. Eldo

    Eldo

    Joined:
    Mar 19, 2015
    I have some Short vids from the Dino runs. I’ll try to get them posted.
     
  7. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    When I was road-racing regularly, the best time at any race meeting was when I was driving home down the highway in my car, without that racket banging in my ears.
     
    maylar and motorson like this.
  8. Atlas Commando

    Atlas Commando VIP MEMBER

    Joined:
    Feb 27, 2018
    I've got a brief visit to Bonneville planned for the bike speed week, probably the most boring ride ever coming up from Houston area. I'm only going to stay a day or two, just wanted to hit an item on my bucket list. I'd love to see and hear a Norton run there.
     
  9. triumph2

    triumph2

    Joined:
    Aug 13, 2008
    From the looks of them I probably will hear them at Bonneville and I live not far from Herb in Ontario :D
     
    Dances with Shrapnel likes this.
  10. Dances with Shrapnel

    Dances with Shrapnel VIP MEMBER

    Joined:
    Jul 8, 2011
  11. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    My bike has a 2 into 1 pipe with muffler and it is TOO LOUD but performs extremely well. The 850 cam is advanced 12 degrees ahead of standard to compensate for the pipe.
     
  12. Dances with Shrapnel

    Dances with Shrapnel VIP MEMBER

    Joined:
    Jul 8, 2011
    Chatting with someone recently who gave some sage advice on the stepped header, particularly with a two-into-one arrangement. I don't understand the phenomena of stepped headers but the simulation he ran was encouraging.
     
  13. Snotzo

    Snotzo

    Joined:
    Mar 12, 2013
    Dances

    stepped headers are/were often used as an alternative to a fully tapered exhaust. Much easier to assemble, and very similar results, although for optimum performance the full taper is to be preferred.
    How many pipe manufacturers are willing to roll and bend tapered headers these days ?
    Skilled sheet metal workers capable of this work do exist, the difficulty is finding one.
     
  14. Dances with Shrapnel

    Dances with Shrapnel VIP MEMBER

    Joined:
    Jul 8, 2011
    Yes, I missed the point of explaining the distinction between stepped headers and true taper.

    I recall Gordon Blair pointing out the step between the bell mouth and bore of the Mikunis on the 500cc twin we were campaigning at the time and saying something along the lines of “confusing” the intake signal. Probably a similar situation on the exhaust.

    So the question has been cast out there and stands.

    Anyone care to chime in?
     
  15. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    There could be something to the edges of the steps helping to prevent reversion of gas flow.
     
  16. Dances with Shrapnel

    Dances with Shrapnel VIP MEMBER

    Joined:
    Jul 8, 2011
    I believe it has to do with discrete signals and when they are reporting back to the valve.
     
  17. Eldo

    Eldo

    Joined:
    Mar 19, 2015
    Well, I've got pics of the finished pipes on the bike at the dragstrip, a vid of the 95hp dyno run and a pic of the actual dyno sheet, but I can't figure out how to (easily, with copy and paste of URLs) post the pics here from my google photos. Most of my stuff is on IG and FB, so if anyone want to see regular updates, follow my Instgram: @santaschoyce, or my Facebook: Andy Cox, Waterloo ON.
     
    Last edited: Jul 10, 2018
  18. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    You can theorise about the effect of steps in the inlet and exhaust tracts, however it is what works which is important. There have been claims that BSA Gold Stars perform better if there is a step in the inlet tract, however the comparisons might have been done while jetting was being changed. Cause and effect can be deceiving. My 2 into1 exhaust is made up of pieces of tube welded together, so there must be welding flash on the interior at the joins. To my mind, the diameter of the pipe is of more importance. Early Triumphs had fat pipes and so did Manxes. My friend was an A grader with the fastest Manx in Victoria. I was once in his workshop and commented on the skinny exhaust on his Manx. He said ' you notice too much'. I've read magazine articles which claim the fatter pipe is better on Manxes, but my friend was the only A grader who ever got close to Ron Toombs on the Henderson Matchless which had a highly developed 4-valve motor.
    I would not use fat pipes on a road race bike, because of the effect on mid-range and bottom end power. But on a land speed bike, they might be good - once you are near top speed. Dyno figures might be important to some people, but what happens in practice might not be what you might expect.
    .
     
  19. xbacksideslider

    xbacksideslider VIP MEMBER

    Joined:
    Aug 19, 2010
    Thanks, Jim. Best wishes for Bonneville.

    By the way, that place is magical. More than mere bucket list.
    Can't be described.
     
    Nater_Potater likes this.
  20. Eldo

    Eldo

    Joined:
    Mar 19, 2015
    [​IMG]

    Our Boyer EI causes a lot of grief with the Dyno software when the dyno rpm sensor is hooked onto the coil, so there are no rpm readings on the chart, but we logged rpm from our WEGO III sensor. Peak HP was just past 7500rpm.