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Thread: Weber IDA 3c question

  1. 11-29-2020, 09:40 AM #1
    Larryg57
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    Weber IDA 3c question

    When fitting oversize 41mm throttle plates to Weber 40 IDA 3c carburetors, what dimension should the throttle body be bored to allow proper fitment of the throttle plates?

    Thanks,

    Larry
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  2. 11-30-2020, 08:25 PM #2
    1QuickS
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    41mm. If you have 41mm throttle valves already then measure them & bore bodies to be 41mm plus 0.001". I prefer to bore then measure the diameter and cut throttle valves to fit. I cut one to check for fitment before cutting the remainder. PS: Good to have a few valves ready for trial & error cutting & fitment. If you already have the valves then they might have localized "flats" on their minor axis to allow installation issues from the throttle shaft being offset from the centerline of the throttle bore. These flats will not allow measurement of the minor diameter length of the throttle valves. It is not a problem to have a little extra diametral clearance, zero clearance is OK if everything is perfect since throttles are opened a bit from 100% closed at idle which naturally provides mechanical clearance between valves and the bore.

    You can over bore to 42mm without issue, larger bores will require replacement of the progression holes.
    Paul Abbott
    Early S Member #18
    Weber service specialist
    www.PerformanceOriented.com
    info@PerformanceOriented.com
    530.520.5816
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