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77 scb 400ci timing

Discussion in 'GM Powertrain' started by socal77k5, Apr 8, 2010.

  1. socal77k5

    socal77k5 Rockstar

    hey ya'll im having problems with my timing again, i had it 180degrees over so i flipped it and still not starting any ideas, i set the #1 at TDC and have teh dist rotor set at point 1 and nothing, when i had it at 180 it back fired and thats about the best result i got all day! any ideas
  2. unplugged

    unplugged Epic Member 5+ Years 1000 Posts

    You need to make sure you have it at TDC for the compression stroke. Trying to set it while at TDC for the exhaust stroke won't work and is a common mistake.
  3. socal77k5

    socal77k5 Rockstar

    what is a good way to know whether its at the compression stroke?
  4. Chris Miller

    Chris Miller Rockstar 100 Posts

    The old 400 generally needs to be set to 4 degrees BTDC. Did you change the camshaft or timing set?
  5. socal77k5

    socal77k5 Rockstar

    no but i did get teh truck started and it starts and runs but wont pass smog now, its at 1250 rpm idle speed, and my canister is ****, i am having a horrible time trying to smog this thing
  6. Mikeandwendy74

    Mikeandwendy74 New Member

    Take out the #1 spark plug.

    Turn the motor over by hand or have someone do it for you, covering the spark plug hole with your finger.
    Seal the hole good, you will feel air push your finger off the hole, this is the compression stroke. STOP.

    Now turn your motor slowly by hand, until the timing marks line up.

    Remove all spark plug wires( I hate when people say DONT DO THAT) Learn your firing setup.

    1-8-4-3-6-5-7-2

    Pop off your cap....if your timing marks are lined up...whichever post your rotor is pointing at is now your # 1. clockwise 1-8-4-3-6-5-7-2

    If you do that, you will ALWAYS have your firing order right on the money. It is impossible to be incorrect.

    One other thing, if you follow these steps and the motor wont start, and fires back through the carb shooting gas etc....

    It could be the gear is in the wrong slot on your crankshaft if you replaced the timing chain and gears. This WILL DEFINETELY cause the backfiring through the carb if its a regular motor setup.

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