TBI Conversion - need timing help!

Discussion in '40- & 55-Series Tech' started by cruiser enthuiser, Feb 9, 2009.

  1. cruiser enthuiser

    cruiser enthuiser

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    In the process of converting my early SBC 350 and I'm trying to set base timing. I'm finding conflicting information on where to set the timing...should it be set to 0 and let the ECM adjust or should it be set to 8 degrees before TDC? By the way, I have disconnected the EST wire while setting the timing so the ECM won't adjust it while I set it.

    Any help is appreciated!
     
  2. black95

    black95

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    I would set the base timing to match the specs for the year of truck the computer came out of. should be able to find that info in haynes or chilton manual. most likely, it is going to be 0 degrees.
     
  3. terrx

    terrx

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    Set it the same as the initial spark advance in the bin. Should be 0 for a stock 7747 bin. What are you using?
     
  4. cruiser enthuiser

    cruiser enthuiser

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    Using the 7747...so set to 0?

    When I put my timing light on it, the timing mark is bouncing all over the place. I've disconnected the EST wire so the ECM shouldn't be trying to adjust, right? What am I doing wrong?
     
  5. terrx

    terrx

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    The 4 character bin code should be on the label on the ECM, or if it's missing look for a sticker on the PROM itself (need to take inspection cover off ecm to see it). Is it stock? Has it ever been reprogrammed? You'll eventually want to know more details about it and possibly reprogram it.

    Verify that the tan/black wire is disconnected at the weatherpack connector near distributor. It sounds like the ecm is still trying to control spark. You could give it throttle and watch the timing - if it advances then the ecm may still be trying to control it. If the tan/black is disconnected it should be steady.
     
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