Holley Idle Transfer Slots

1. Holley Idle Transfer Slot Adjustment
2. Holley Idle Transfer Slot Tuning
3. Youtube Holley Idle Transfer Slots Free
4. Holley Idle Transfer Slot Restrictor
5. Holley Idle Transfer Slots
6. Holley Idle Transfer Slot

Transition slot exposure is critical because it affects both idle quality, idle air / fuel mixture as well as 'tip-in' or 'off-idle' response.
Too little or no transition slot exposure on the primary side on most engines will cause a stumble or hesitation on tip-in. Viewed with the butterflies in the idle position, base inverted.
Click on picture to enlarge

Set idle speed as low as reasonably possible to avoid entering the off-idle circuit. Off Idle – Just above idle at very light throttle positions, the transfer slot now provides the fuel. Idle feed restrictions and idle air bleeds are used to tune this circuit. I got it all back together over the weekend. I need to pull the carburetor back off and readjust the secondary throttle plates, i couldnt get it to idle happily under 1500 rpm, pulling 13 inches of vacuum. I have too much transfer slot showing on the secondaries, i was able to shut the primary throttle blades all the way and still have the car. Unfortunately, when the curb idle adjustment is opened past the stock setting, the throttle blades uncover the transfer slots. These slots are intended to pull additional fuel from the carburetor's.

Too much transition slot exposure on the primary side on most engines will cause: a rich idle / exhaust smell; little to no sensitivity to idle mixture screw adjustment; soft tip-in stumble or hesitation on tip-in or part throttle response.
Click on picture to enlarge
The following picture shows a near perfect transition slot exposure for most engines. The shape of the transition slot exposed (under the butterfly) will look something like a square.
Click on picture to enlarge
To adjust secondary transition slot exposure a secondary idle screw / throttle stop is provided. On TMP Carbs' preppared carbs, the idle speed screw is accessible from the top. To access it, with engine off, simply open the throttle to expose the secondary idle speed screw and turn.
Idle Fuel Restrictions (IFRs) or Idle Jets

Holley Idle Transfer Slot Adjustment

Replacement of 'idle fuel restrictions' (IFRs) also referred to as 'idle jets'.
IFR's (idle jets) on TMP Carbs' prepared Holley carburetors utilizing Holley metering blocks are located as indicated in the diagonal passage intersecting the idle well providing communication to the idle passage in the metering block face. TMP uses 6x32 brass set screws for the IFRs.

Holley Idle Transfer Slot Tuning

Power Valve Tuning

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Holley Idle Transfer Slot Restrictor

Power valve tuning is critical for best mileage, throttle response and performance. By far, most high performance and racing engines require a late opening, low value power valve such as a 2.5 or 3.5. The proper power valve value can be determined by measuring manifold vacuum when accelerating from a dead stop or low speed taking note of the vacuum reading as the secondary barrels begin to open.

Holley Idle Transfer Slots

Holley Idle Transfer Slot