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Engine intake runner length?

  1. Mar 11, 2007 #1
    I'm currently adapting a rack of four 36mm carbs to a 1.6L (97.64 ci) 4 cylinder engine. I'm trying to figure out how to calculate the proper intake runner length to use. This is to be a zippy daily driver, not an 1/8th mile drag car. I've found information on "Independant Throttle Bodies" length calculations for fuel injected systems, but this involves a plenum and does not seem relevant. Any help would be much appreciated.:smile:
  2. jcsd
  3. Mar 12, 2007 #2


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    Gold Member

    I can't help with any formulae. As a general rule, however, your power band is partially governed by the runner length. Longer means your band is in a higher rpm range.
  4. Mar 13, 2007 #3
    As far as I know the whole secret of side draught carbs are in the fact that they have very short intake manifolds producing power from a very low rpm. range. part of the m3 power is the 6 individual throttle bodies mounted directly on to the engine. Suggest you make the runners as short as possible.
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