Different authors/companies use different terms for the Economizer. Carter calls it Economizer, Rochester the Idle Channel Restriction on the QJ. In his QJ book, Ruggles calls it the IDC. In Roe's QJ book, he calls it the ICR.
The Comp Series 750 AFB I had did not have any king of Allen Key type set up near the mixture screws to limit travel. This was an original 4XXX series carbs. I believe some later model AFBs were released that had the 'Competition Series' sticker across the front of the airhorn, but were 9XXX series. Is this what you have?
The IDC/ICR restriction controls premixed air + fuel, which is delivered to the T slot. If you enlarge it, more A/F is available & vice versa. Usually a 0.040-0.060" hole size. At idle, with T slot position correct, the area of T slot above the blades is much greater than a 0.060" hole, so the ICR hole controls the flow. Enlarging this hole makes more A/F available to the T slot. So I could see this change affecting the idle mixture [ requiring adjustment with the mixture screws ] depending on the amount of T slot showing at idle. Hope this answers your question.Statistics: Posted by GTO Geoff — Mon Jan 24, 2022 6:22 am
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