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Fat Idle & Lean Cruise

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  • Fat Idle & Lean Cruise

    Hello. I recently swapped to a Quick Fuel 600 on the 305 in my pickup. Itís a stock LG3 with long tube headers, Edelbrock Performer EPS intake, and 1Ē phenolic spacer. Air cleaner is a raised base 14x3 so thereís enough room over the bowl vents. Fuel level is centered in front bowl. I changed the power valve to an 8.5 and had to bump up the squirter to a 36 to get rid of a lean stumble. Timing is 12į BTDC and 32į total by 3000.

    At idle, the leanest I can get it is around 12:1 (forgot exact number), but around 1500-2000 RPM in 3rd gear it leans out to around 16.5:1 at worst. It runs well enough to drive around and is almost spot on at wide open throttle. Iím concerned about the lean spot with winter coming and putting a larger idle feed restrictor as I understand it will make the idle mixture worse.

    The factory primary IFR is a 31, idle air bleed is factory 63. I put a 61 IAB trying to enrich the lean spot and it went dead lean on my gauge and the engine cut out and then pick back up under light acceleration. Also tried a 59 IAB but the idle was so rich it didnít want to run. Any ideas where to start? Thanks.