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Old 07-21-2011, 09:17 PM
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Quick Fuel idle mixture screw adjustment Help

I have a new QF SS-750 mechanical secondaries carb on a new 383 thats in a 82 c10. I have yet to drive the truck yet but it is running pretty rich at idle so I figured I'd adjust the idle mixture screws but am unsure on how to properly do so. If I understand correctly it is obtained by achieving the greatest amount of vacuum with slight turns of each screw. Here is the jetting, power valve, and etc. specs.



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Old 07-22-2011, 01:15 AM
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Since I don`t know your combo, first things first. Make sure you have enough initial timing in to keep the idle low enough so it doesn`t pull fuel from the main boosters. If this is out of the way then we can proceed.
The idle is set one per side, start by moving the idle adjustment all the way in and LIGHTLY let it seat, then slowly come out until it reaches it`s highest vacuum,, trick to the trade is you have to count how far you came out per turns, sometimes it`s a half turn, sometimes it`s a turn and a half, but you get the idea. With the count in mind, move to the otherside and move it out the same count as the prior side. Now, check your vacuum gauge. What I usually do after both sides are set is first go lean slightly with both sides and see if the vacuum increases, if not, I`ll go slightly to the rich side and see if it increases. If neither make it better I`ll leave it where the original setting was. However, if you don`t like to play around with it as I do then you don`t have to worry about moving either side for further fine tune once you have both sides set equally.
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Old 07-22-2011, 01:34 AM
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It's a 383 stroker: Procomp heads (I know, I know had em cnc'ed, port, polish and built em with Comp Cams rollers) Crane Blue Racer 1064.. 234/244 488/510..112 ls, forged rotating assembly(Scat, Probe) , air gap intake, QF SS 750...Total timing 36 deg

I have 4 way idle mixture screws (double pumper).
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Old 07-22-2011, 01:59 AM
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Try this then and apply it to all 4.
http://www.chevyhiperformance.com/ho...638/index.html
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Old 07-22-2011, 04:09 AM
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hey Double Vision,

Thanks for the great link on idle mix settings!

Very informative and straightforward.

Again thanks.
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