Dwell and timing set. Crisp take off and power! BUT rattles on acceleration.

Discussion in 'Wrenchin' Secrets' started by garybuick, Dec 27, 2009.

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  1. garybuick

    garybuick Time Traveler

    Ok, this part i wasnt clear on. I thought the adjustment determines HOW MUCH advance the vac adds, not at what vacuum it adds it.


    So then, if i have the screw backed all the way out it adds vac advance at low or high vacuum? I have to check that and see it it adds more or less vacumma t different screw postions. I could have sworn it did.
     
    garybuick, Jan 7, 2010
    #61
  2. CJay

    CJay Supercar owner Staff Member

    I would imagine a Mity Vac would come in handy for this procedure
     
    CJay, Jan 7, 2010
    #62
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member


    Jim is referring to the Crane adjustable canister. They no longer make it as Crane is out of business now. You may still be able to find them though. The Crane unit used an adjustable cam that limited the amount of advance the canister delivered. In addition, there was an adjustment through the vacuum nipple that adjusted the spring tension. In any canister, the spring opposes the vacuum pull. Engine vacuum must overcome spring tension to advance the timing. The stiffer the spring, the higher the vacuum must be to initiate advance from the canister. This is a handy adjustment to have when you have lower vacuum from a performance cam. It adjusts when the advance comes in, and when the spring pulls it out.

    I believe you have the Acell unit. There is one adjustment through the vacuum nipple. It adjusts the amount of advance, but I'm not sure if it affects spring tension. Read the instructions that came with the unit and see.

    Your mechanical advance should be mostly linear. It shouldn't go up quickly at 1200, and then go 2-3* at twice that RPM. Either the springs are too loose, or there is a bind somewhere.
     
    LARRY70GS, Jan 8, 2010
    #63
  4. garybuick

    garybuick Time Traveler

    ya i have the accel the adjustment seems to limit vac advance. all the way backed out = about 5 deg and goes up from there.

    Today I took the weights off and cleaned them bright, then cleaned the pivot pins bright and holes in weights. There is no bind at all. I cant figure out why it doesnt just go up to its max and stay. It always advances 2 or 3 deg about 1200 rpms later. So im not sure what to count as 'all in'.
     
    garybuick, Jan 8, 2010
    #64
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