70 LT-1 tinkering again (Duke) - NCRS Discussion Boards

70 LT-1 tinkering again (Duke)

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  • Dennis D.
    Extremely Frequent Poster
    • March 1, 2000
    • 1071

    70 LT-1 tinkering again (Duke)

    Ok. Think Im getting a handle on the vacuum/ timing. The rebuilt carb is on. The B28 can and black springs installed . First result was a bad fuel smell, smoking. and black soot in the exhaust tips.

    Pulled all the plugs and was surprised they weren't bad. cleaned them up, reinstalled. Decided to adjust the fuel mixture from 2 1/2 turn out to 2 turns out. Fuel smell went away, no more smoke or soot. Vacuum also up to 13". I didn't take pics of vacuum readings, but plugged it was 11" and hooked up it was 13". I'm assuming the 38 total is 18 initial+ 16 vacuum+ 4 degrees mechanical slipping in there.
    Next is to get initial and mechanical set to 38* WOT.

    I took a couple of readings.
    20200503_143303.jpg
    20200503_143018.jpg
  • Duke W.
    Beyond Control Poster
    • January 1, 1993
    • 15661

    #2
    Re: 70 LT-1 tinkering again (Duke)

    The photos will not completely download to my computer.

    At what RPM did you get those vacuum readings. Idle vacuum readings without specified the idle speed are MEANINGLESS.

    Did you connect the B28 VAC to a full time vacuum source for normal operation?

    Total WOT advance is set with the VAC signal line DISCONNECTED AND PLUGGED WITH A GOLF TEE OR EQUIVALENT. Determine the start and stop revs for the centrifugal advance. I'd like to know. Then rev the engine a few hundred revs above the point of max centrifugal and set advance as high is the 36-40 range with a dial back timing light as the engine will tolerate without detonation.

    Total WOT throttle advance = initial + full centrifugal. (36-40) Manifold vacuum at WOT is near zero so there is not contribution from the VAC.

    Total idle advance = initial + full vacuum + plus a few degrees centrifugal if it starts below idle speed. Low 20s to low 30s. Low overlap cams in the lower part of the range, high overlap cams in the upper part of the range.

    Maximum cruise advance = initial + full vacuum + full centrifugal... 52-56... may not be achieved on engines with lazy centrifugal curves and tall gears.

    Duke

    Comment

    • Dennis D.
      Extremely Frequent Poster
      • March 1, 2000
      • 1071

      #3
      Re: 70 LT-1 tinkering again (Duke)

      The pics show both degrees and rpm.
      Plug vacuum =18degrees @815rpm (11"vac)
      With vacuum = 38 degrees@875rpm (13"vac)

      Comment

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