Setting vacuum advance

Discussion in 'General Maverick/Comet' started by satchelmcqueen, May 16, 2019.

  1. satchelmcqueen

    satchelmcqueen Member

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    Ok so as I understand it and have gathered from reading all day yesterday here's basically how it goes for a stockish/mild 302.

    First set base timing around 12deg with Va.c. Adv unplugged. Then plug vac adv back up. Using timing light hold rpm at 3000rpm and see what deg you have. Then adjust vac adv until you have about 32-34deg at 3000 rpm.

    Is this correct?
     
  2. yellow75

    yellow75 MCCI Oregon State Rep Supporting Member

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    Sounds right to me you may even want to take it up a little more its one of those things that driving it will tell if it likes more or not. I would want to have a vacuum gauge hooked up just to see what the difference is. You will probably need to adjust you carb after setting the timing as typically any time you change timing carb needs to be adjusted and the vacuum gauge comes in handy for that
     
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  3. Acornridgeman

    Acornridgeman MCCI Wisconsin State Rep Moderator Supporting Member

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    I set mine with vac advance plugged - for both the initial and all in from the mechanical at specified RPM. Once that is all set I hook the vac advance back up and just let it do its thing.
     
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  4. satchelmcqueen

    satchelmcqueen Member

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    Ok ive read I can do that as well.
     
  5. Crazy Larry

    Crazy Larry Member

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    I run 37-38 total. I really wouldn't worry about the vacuum advance unless you're getting detonation.
     
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  6. satchelmcqueen

    satchelmcqueen Member

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    Can you tell me exactly how you set yours? I assume you set total at 37-38 at 3000rpms and possible set vacuum canister in the middle?
     
  7. Krazy Comet

    Krazy Comet Tom

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    Basically at more than 15-25% throttle opening, most engines have little if any vacuum, thus no vac advance. The larger the carb and cam, the less vac there is at any given throttle opening.

    Set up base for around 12-14* then adj mechanical advance for 36-38* total at 2800-3000 RPMs. Test under varying throttle conditions and temps for response and ping. Once engine is running at it's best, tweak vac advance so under light throttle(cruise) it adds another 10* and drops out as throttle is opened. If you get ping under light throttle, reduce vacuum advance. If it pings when vac advance is added, knock out a couple degrees at a time till ping stops. Point is, no one setup is best for all engines, transmission ratios, rear gear etc.

    When Mr Roberts sees this, he can fill in full details.
     
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  8. Crazy Larry

    Crazy Larry Member

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    I set mine for 12 initial, and I have 26 in the centrifugal, which totals 38. I never messed with the vacuum advance, but I was told it's about 10 degrees.
     
  9. stumanchu

    stumanchu Stuart

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    I set my initial to 24, centrifugal is limited to 12 and all in at 2800rpm for a total of 36. My vac pot comes apart (I have an old points distributor that fires a TFI module) and I added washers to it to limit it to 12 degrees. I have not heard any pinging.....and I have relatively quiet exhaust. Plugs are gapped at .042
     
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  10. Krazy Comet

    Krazy Comet Tom

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    Have you tried a hot restart on a really hot day?? My experience is anything over approx 16* will cause hot starting problem. Of course it's somewhat dependant on cam duration, compression, starter torque, battery capability, size of cables, etc.

    I ran my T-Bird at 36* but had a ignition kill switch. I'd start cranking engine, then flip on ign.
     
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  11. Crazy Larry

    Crazy Larry Member

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    I
    I agree, unless you have the Duraspark-II ignition with the blue gromet. It has a start retard feature.
    That said, anything over 20 (initial) is too much for a street engine.
     

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