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Old 10-27-2005, 10:15 PM
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A/F idle mixture ??

Ok so on most holleys that I have had to adjust, I have noticed that one side will screw all the way in and out without any effect and the other side effecting it greatly, thats the way all holleys have ever worked for me. my 600 edelbrock tuned great with both screws, but when I upgraded to a 750 I got the same thing as with the holley. one side effects hardly at all but the other side does a lot. am I doing something wrong?

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Old 10-28-2005, 09:22 AM
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Usually when this condition occurs it`s flooding on that one side due to excessive fuel pressure, too high float setting, or partially stuck needle and seat, or low spark timing which calls for a high idle setting that`s high enough to tip in the primary side. at idle shine a light in the carbs throat, see if you see any fuel dripping out of the boosters.
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Old 10-28-2005, 09:35 AM
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This occurs when the throttle blades are open into the main circuit (pass the idle circuit). In order to get more air into the engine with the throttle blades in the idle circuit (more closed), you should remove the carb and drill a small hole in each of the front throttle blades. I normally use a 0.090 or 0.100 drill bit. Sounds strange but Holley even shows this in their "how to tune" hand book.

If you get vacuum on the ported vacuum source on the carb, the throttle blades are pass the idle circuit and into the main circuit. You can also tell by looking down into the carb to see if the blades are opened pass the little idle slots in the throttle bore.
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Old 10-28-2005, 10:47 AM
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if its dripping out of the booster is that the primary or idle circuit? also if I drill in the butterflies, will I be able to tune it out by richening the af screws or am I taking a chance of needing to buy new blades after drilling them if it doesnt work. so the side that doesnt change when adjusted would be the side getting to much fuel due to pressure problems or blades possibly being open a little. right? I dont have any vacuum on the ported side at idle.
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