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AFR for smooth idle 11.5 or 12. Too rich

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  • AFR for smooth idle 11.5 or 12. Too rich

    Hi,

    I have a Ford 302 that bored and stroked to 332CI
    edelbrock performer heads
    edlebrock 2221 cam
    pro flo 4

    Firstly, I’m trying to figure out the initial timing. It seems to idle well at any!!! 18 to 36! Now, I’ve found a sweet spot of 24 degree initial. Vacuum advance is set to max which is 15 on the new update. Total is 36. Pulls well. Accelerates nicely. My question is that I didn’t hear any pinging even when I advanced the initial to over 30. I degrees the cam when I installed it and came in perfectly at 107 for that cam. Just wondering if a too advance cam timing can result in such a high initial spark timing? Anything under 18 and it idles like a pig.

    secondly..... The engine only runs smoothly when the idle AFR is at 12. It used to be better at 11.5 but I cannot set this low on the new update. It’s stinks though, way too rich from the exhaust. It’s eye watering. If I’m driving in town and idling a lot, the plugs foul up in no time and then runs really bad. Cleaned the plugs several times and replaced them. Put an MSD ignition on too with hotter spark plug but not difference. It I set the AFR to over 12.5, it vibrates like crazy.
    thought it was a dead cylinder. Did a compression test and all good. It’s a new build. Though maybe it’s a vacuum leak and checked that too. I’m at a dead end.

    can anyone help?

    thanks.

  • #2
    Yes, you can more or less expect that an advanced cam might like a little more timing advance at idle since the intake valve opening/closing events are occurring sooner.

    Your idle AFRs are insanely rich. You say any leaner than 12.5 and it vibrates like crazy? What does that mean? I'd expect a fair amount of lope and possible engine movement at idle with the #2221 cam - it's pretty rumpty-dumpty: https://www.youtube.com/watch?v=z4cfPw4l8yo What is the vehicle and what kind of engine mounts do you have? This may be more a mechanical engine install issue and nothing really related to the Pro-Flo 4. I'm wondering if you're attempting to smooth out what's going to be a fairly rough idling engine by running excessively rich with a lot of timing advance. If you want a really smooth idling engine, you might have to reconsider your cam selection.

    If you want to give us a better idea of what's going on when running the engine, give this a read: https://forums.edelbrock.com/forum/p...-a-data-logger
    Also, what cal are you running?

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    • #3
      What is your vacuum at idle?

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      • #4
        id triple check the firing order , and kill each cylinder 1 at a time, to make sure its firing on all 8. Watch the digital tach each time you remove the plug wire for rpm drop/change in iac. A misfire can lead to erroneous afr readings.

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