Intake Modifications

Discussion in 'Performance Mods' started by andyinchville1, Nov 4, 2007.

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  1. Hi all,

    Having made some headway on my tuned pipe / expansion chamber (pics on site), my attention is now turned somewhat on the intake portion of our engines....While I realize that many here have possibly upgraded
    to different carbs....I am wondering if we can modify our stock carb and change the intake header to achieve better performance...

    1) The stock intake manifold is not port matched and has some radical bends in it.....I am thinking of fabbing up an intake made of either 3/8 or 1/2" pipe with smooth bends and will have to somehow match the intake header to the cylinder port....I am thinking I will use the smaller diameter (3/8 inch) to keep velocities high for our low (relatively speaking) RPM's and weld it to the 1/2 pipe that would be squished somewhat (ovalized) to better match the intake port...Additionally I would lengthen the intake runner and angle it off to the side for more "ram" effect and to provide more room for a large air filter to be added to the carb (maybe an open element oiled cotton filter).

    2) As far as carb mods....I think I would simply upgrade the air filter (see above)....can anybody recommend a good airfilter that would fit our little engine (dax 70)....NOTE: although inelegant, I was thinking of using a Plumbing reducer and welding it to the air intake flange and using a high perf
    pocket bike air filter by clamping it onto the reducer flange...

    3) Any ideas on what the ideal carb size in mm should be?....I am thinking
    a smaller (like our stock carb) would be fine for our lower RPM's but have even toyed with the idea of running 2 stock carbs off a "y" on the intake header...I figure that way maybe we'd have the benefit of a smaller carb (higher velocities) for low speed but have the 2n'd one kick in if needed higher up in the RPM range....of course at that point the weak link would be the small intake header?....Hmmm

    Any ideas before I try fabbing?


  2. OOPs....I thought I was putting this in the wild in the streets section....

  3. mickey

    mickey Guest

    For the filter, this VC is working well and should accept your choice of pocket bike filters.
  4. Thanks...I'll have to see it it fits the dax 70 carb...
  5. dave1490

    dave1490 Guest

    that,s what the old 389 goat,s [g.t.o.}had.a 6 pack mostly running off the center 2 barrel,then using the other 2- 2 barrels for power.
  6. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Andrew, go find two carbs jetted and sized to feed 23cc ZENOAH engines or smaller. install separate fuel and throttle connections. control one carb until upper midrange. then yank both cables for high rpm/top speed.

    the most difficult tasks would be to fab the intake manfold...ANNND tuning this puppy.

  7. Hmmm....interesting....;-O.....

    I had a couple free hours today and started making the tubes / mounting plate for the new intake....