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Conference napalm::musclecars

Title:Musclecars
Notice:Noter Registration - Note 5
Moderator:KDX200::COOPER
Created:Mon Mar 11 1991
Last Modified:Mon Jun 02 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:182
Total number of notes:5467

134.0. "Offenhauser "Dual-Port" questions" by COMET::BUSSARD (You Crack Me Up!) Wed Jun 01 1994 17:07

    
    Comet::Bussard
    CXO1-2-131
    DTN 522-2144
    
    I inadvertantly picked up the wrong used PERFORMER manifold,
    without the oil tube in the front as needed.  I'm  looking at a
    trade for an Offenhauser "Dual-Port".  This thing has the oil
    input in the front for the early 283 SBC, and of course is a 
    dual-plenum for the street.  But,  it's got the weirdest intake
    feeds I've seen.  It appears the primaries have one port,  and
    the secondaries get the other port, as they are stacked:
    
    Intakes to head looks like this:
                                   
    
    ____      ____      ____      ____
    |  |      |  |      |  |      |  |       <= secondaries
    |  |      |  |      |  |      |  |
    ====      ====      ====      ====  <=  port split throughout w/plenum
    |  |      |  |      |  |      |  |
    ----      ----      ----      ----       <= primaries
    
    Anybody ever use/see this intake manifold? Pros/cons for this head
    ASAP would be appreciated,  as I would like to see this thing on 
    the motor if it's a good intake.  I'll be using it at 6000' above
    seas level,  with a slightly hotter cam than stock.
    
    Lemme' know, and thanks in advance!
    Rob
    
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134.1Torquey manifoldUSHS01::HARDMANMassive Action = Massive ResultsWed Jun 01 1994 21:5720
    Rob, that intake is supposed to make great bottom end torque. The idea
    is that the long, small 'primary' runners will have excellent air/fuel
    velocity at low rpms. This helps stuff the mixture into the cylinders.
    
    As the secondaries kick in, the larger runners also come into play to
    let the engine really breathe at higher rpms. It's supposed to give you
    the best of both worlds, with a broader torque band. 
    
    The dual port manifold was supposed to be the hot ticket for trucks and
    heavy cars, due to the low end torque boost. I would suspect though
    that it doesn't flow as well at high rpms as the Performer due to the
    loss of cross sectional area induced by the divider.
    
    You'll have to make the final decision, depending on how you plan to
    drive the car. The dual port will probably be fine in daily driving.
    The Performer will probably do best at the drag strip. A heavier car
    will probably let the dual port really shine. Decision time... ;-)
    
    Harry
    
134.2Offy news flashCOMET::BUSSARDYou Crack Me Up!Thu Jun 02 1994 11:5226
    
    .1 is correct.  I found this Offy in an old PAWS catalog, and I believe
    I'll pick it up tonite.  I'll be using it in daily driving,  and the 
    car weighs in at 3300, dry.  There are two models,  a 6007-DP for 
    std. 4-bbl,  and the 6008-DP for the Qjet spreadbore. Hopefully
    this one is a 6007.  
    
    The Offy selection chart in PAWS shows the dual-port as having "max
    torque' beginning at 2000 RPMs, ending at 5500 RPMs, with "Max
    working horsepower" beginning at 500 RPMs,  ending at 5500 RPMs,
    with a 600 CFM carb.
    
    This is a wild looking intake,  all blocky looking,  quite unlike the 
    'spidery' look that we typically see in an intake.  This is because of
    the port sizes involved.  Also,  an added benefit is that the
    secondaries are insulated from heat by the primaries, so secondary 
    air is cool and dense.  And supposedly,  if the hype is correct,
    the secondary mix is "shoved" past the intake valves by the
    velocity of the already moving  primary mix.
    
    New in 1982,  this intake listed at $149.00 then.  I think I'll get
    it now.
    
    Thanks,
    
    Rob