Struggling With Understanding Engine Timing Concepts

Discussion in 'Engine Topic' started by Bandit723, Jul 24, 2017.

  1. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    Have read thru numerous posts on this topic. I get the vacuum advance theory but what is out on the internet seems to be a bit vague when it comes to to figuring out the mechanical advance settings or what total timing really is.

    So example my mechanical all in dist set and locked at 28 degrees advanced all in but am idling at 16 degrees advanced what is my total advance when running all in?

    So no matter how i set the idle advance i end up with 28 degrees so 10 advanced at all in still times out to 28 and 20 advanced still times out to 28.

    Have seen a number of calculations that spell this out so just looking so is is my total timing 28 degrees with a mechanical advance of 8 degrees 28-20 = 8 or is it 28 total? or is it 28 + 20 for a total of 48 degrees.

    Not the best question but just looking to understand this.
     
  2. biker

    biker Veteran Member

    Your vacuum advance must be disconnected in order to know what your actual initial timing is. Sounds like you are getting some advance from vacuum if you can change total and not get much diff on initial reading.
    Your distributor has a certain amount of mechanical timing bult into the mechanism. As revs go up, this advances until it hits its limit. Whatever you add to that by setting initial timing at idle is the total timing. When driving, any vacuum advance you have will disappear whennthe engine is loaded at full or mostly full throttle.
     
  3. biker

    biker Veteran Member

    How are you setting your total timing? Using a dial back light or totally marked harmonic balancer?
     
  4. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

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    But if his Dist.Is locked,
    Vacuum wont work correct?
    Ive nvr ran a locked out Dist.
     
  5. Bandit723

    Bandit723 Veteran Member

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    Should have clarified i am not using any vacuum advance so still unclear what the total advance is.
     
  6. Bandit723

    Bandit723 Veteran Member

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    Correct
     
  7. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

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    belding,mi USA
    Seems to me his total would be 28 then
     
  8. Bandit723

    Bandit723 Veteran Member

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    I do have a dial back light and good marks on the on the balancer. so 16 on the light = 0 on the timing marks 28 on the light = 0 on the timing marks.
     
  9. Bandit723

    Bandit723 Veteran Member

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    I would think so but just not sure.
     
  10. 80sz

    80sz Veteran Member

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    Timing total is what you have on crank + mechanical built into distributer + what the vac advance pulls. Using a dial back timing light see what crank reads then rev up till advance stops. hold that rpm,starting at zero turn dial up on light till it reads what you had on crank at idle. The mark will move backwards . What it says on light will tell you how much mechanical is built into the distributer. Then at part throttle the vac canister will pull a additional 10-15 degrees. At wot there is little vac so the canister wont add anything. If you got 15 on crank + 21 mechanical you got 36. Then the canister will add 15 to that giving a total of 51. The vac advance is only for part throttle conditions. A typical distributer has 21 degrees built in.
     

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