Starter Covers & Airboxes

Discussion in 'Airheads' started by gsjoel, Feb 20, 2013.

  1. chasbmw

    chasbmw Long timer

    Joined:
    Feb 19, 2006
    Oddometer:
    2,704
    Location:
    Bath Uk
    Dells, a true 40mm exhaust pipe, Jim Cray 40mmsilencers, twin plugged squish checked, ported, Seibenrock 1070 etc etc. nearest I could get to an 80s hot rodded airhead, but using some of the parts than have been developed since.
    #41
  2. Rob Farmer

    Rob Farmer Long timer

    Joined:
    Aug 27, 2002
    Oddometer:
    6,767
    Location:
    Loughborough, Leicestershire. England
    That's just what I'm putting together at the minute. Right down to the 40mm exhaust system. I'll be going with the clamshell airbox, amal carbs and a 336° Cam.
    #42
  3. supershaft

    supershaft because I can

    Joined:
    Sep 9, 2010
    Oddometer:
    9,116
    Location:
    San Francisco Bay area
    Not my experience at all. My airbox experiments had the same results regardless of whether or not I had a 32mm Bing or a 38mm Dellorto. A 308 cam or a 336 cam. Stock mufflers or Staintune Sports. Going from one small/one large to two larges horns killed my midrange. No horns killed it worse. A variety of shortened horns and holes in the top like the picture above all did my midrange NO good. It ran by far the best with the one small/one large stock top. Just about perfect in fact. On a dyno and off.

    Then everything changed when I raised my CR to a calculated 10.0:1, dual plugged and remapped the ignition curve, went from 42 to 44mm intake valves, and really changed my port shapes. The same above experiments didn't hurt my midrange so much and got me gains on top. A few more tests and I am now running no top at all and my stock velocity stacks are shortened so the the bell mouths are just inside of the box. I have got super strong midrange with a setup that before would have killed it! It all depends.
    #43
  4. chasbmw

    chasbmw Long timer

    Joined:
    Feb 19, 2006
    Oddometer:
    2,704
    Location:
    Bath Uk
    I trust that you will contribute your dyno charts to the debate
    #44