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  1. #11
    Exceeded sell by date Plumpcars's Avatar
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    Running without vac advance will not cause any damage. As a test try connecting it to full vacuum rather than ported, see what that does. Ported was introduced as part of some emission changes, prior to that engines were running full vac source.

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  3. #12
    Rods 'n' Sods Junkie Gazza51's Avatar
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    Quote Originally Posted by Plumpcars View Post
    Running without vac advance will not cause any damage. As a test try connecting it to full vacuum rather than ported, see what that does. Ported was introduced as part of some emission changes, prior to that engines were running full vac source.
    I'll try full vac tonight

  4. #13
    Rods 'n' Sods Junkie Gazza51's Avatar
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    Ok, had a little play again this evening.

    I checked various degrees BTDC and also checked the Total

    5 int = 31 total
    7 int = 33 total
    9 int = 32 total
    11 int = 34 total
    13 int = 36 total
    15 int - 38 total

    all total read at 3000rpm

    I roadtested at 13 int /36 total with the vac/adv disconnected and the performance was much better, when i connected the vac/adv it ran very rough at 2000rpm so i disconnected the vac/adv again.

    I'm happy to run with no vac/adv but I'm puzzled by the rough running

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  6. #14
    I'm Not Jed Clampett stueeee's Avatar
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    Quote Originally Posted by Gazza51 View Post

    I'm happy to run with no vac/adv but I'm puzzled by the rough running
    The rough running was caused by the vac can causing the motor to be over over advanced in the mid range.
    Stuart.
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  7. #15
    Rods 'n' Sods Junkie Gazza51's Avatar
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    Quote Originally Posted by stueeee View Post
    The rough running was caused by the vac can causing the motor to be over over advanced in the mid range.

    A problem with the dizzy then ?

  8. #16
    I'm Not Jed Clampett stueeee's Avatar
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    Quote Originally Posted by Gazza51 View Post
    A problem with the dizzy then ?
    Not necessarily, it's just that your particular motor doesn't need the extra advance being contributed by the vacuum can during mid range running.

    If you think about what's happening in the motor, the less advance you need at any given revs, the better the combustion (so power and and efficiency too) must be.
    Last edited by stueeee; 28-03-2012 at 06:57. Reason: more added.
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  9. #17
    Rods 'n' Sods Junkie Gazza51's Avatar
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    Thanks Stueeee

    I will try the same with the Vette tomorrow, that has similar characteristics.

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