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Thread: Idle refinement for 360 SBC with auto transmission.

  1. #1

    Default Idle refinement for 360 SBC with auto transmission.

    I'd appreciate suggestions on getting my idle settings right. I've experimented with them and mostly it's running good, but sometimes it surges at idle, searching for the A/F ratio maybe. Also, at times I notice surging when cruising at very low load - say 2nd gear puttering in traffic. WOT, off-idle performance & highway cruising are great. A good solid idle at 650-700 would really help with pushing at intersections due to the low stall converter and overall driveability.

    The car is an El Camino with .060" over for 360ci, Vortec heads, a SUM1103 (Advertised Duration 288°/298°, Lift .444"/.466', 112° LSA). MSD ignition box & Atomic EFI. Transmission is a 200-4R with a standard converter. I recently saw an improvement by changing cam from Mild to Street/stock. Some of my settings are:
    8 cylinders
    360 cubic inch
    Cam - Street/stock
    A/F Idle - 14.0
    A/F Cruise - 14.0
    WOT - 12.8
    Boost - 11.9 (Not sure what this is.)
    Pump squirt - 27%
    Power valve enrich - 24%
    The IAC at idle is 13% in Park and 35% stopped in gear. I feel that I'm very close, just need help to get over the top with this.
    UPDATE: The IAC values were taken before the engine was fully warmed up. Here are the actual ones probably indicating the throttle plates are too far open: IAC in Park = 0 (RPM 775 with target of 725 now) and in Gear = 18.

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,483

    Default

    You need to close the throttle blades until you have at least 5 steps open while in Park.
    While the IAC is at 0, the ECU is trying to give the target idle, but it can't run any slower.
    You also need a looser torque convertor than stock, with a cam like that. Gary
    Last edited by Gaz64; 08-19-2019 at 07:45 PM.
    Regards, Gary

  3. #3

    Default

    It's running pretty good. Do my AFR, squirt, or power valve settings seem good or do they need adjustment?
    I'd agree on the torque converter comment, others have suggested that this cam needs a looser setup. Ed
    Last edited by eduardo69chevelle; 08-19-2019 at 01:56 PM.

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