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importance of Vaccuum Advance?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by KRAZIE87K5, Sep 25, 2001.

  1. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    OK - after looking at the Four Wheeler, I noticed they suggest a distributor upgrade... I have done this already, but I have a Mallory Unilite distributor that does not have vaccuum advance. What am I loosing out on here?

    I don not have a MSD box (yet), or any other after market ignition stuff. Should I get a vaccuum advanced distributor?

    <font color=red>Just give me a tank, and point me in the right direction!</font color=red>
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  2. RedDwarf

    RedDwarf 1/2 ton status

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    No vacuum advance means the advance is computer controlled<P ID="edit"><FONT class="small">Edited by RedDwarf on 09/25/01 10:29 AM.</FONT></P>
     
  3. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Um - well you make the question sound pretty stupid I guess!

    I don't have a (functional) computer. My truck has no computer sensors or anything else...

    So if I have no sensors - and no vaccuum advance - I would have to then say based on your information - that I have no advance at all! Hmmmm.... I am guessing also that this would be a bad thing? Could this be why the truck has no torque when you hammer it? Or does the advance have more affect at higher RPMs?

    Threads like this one really humble what one might think they know about mechanics... Sometimes I find it scary that i built my truck!!!

    Do I have to pull my non-advance type distibutor for something that can provide vaccuum advance? This is getting serious now!

    <font color=red>Just give me a tank, and point me in the right direction!</font color=red>
    <font color=blue>DONT MESS WITH AMERICA!</font color=blue>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
     
  4. BorregoK5

    BorregoK5 1/2 ton status

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    Well, your not fully advanceless, you still have mechanical advance in the ditributor which will help a little with the higher rpm power but the vacuum advance is what adjusts for load on the engine. If you can't get a vacuum advance unit on your distributor then retard your timing a bit so as to have the power at bottom end and give up a bit of top end.

    What, Me Worry?
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  5. muddin4fun

    muddin4fun 3/4 ton status

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    Hmm...if you're running a BB and you don't seem to have any power, that could be the problem. Check and make sure it's not mechanically advanced before you go and buy another distributor.

    If you see my truck on a trailer, call 911 cause it's <font color=red>STOLEN!!!</font color=red>
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  6. Thunder

    Thunder 3/4 ton status

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    About the only thing you are loosing out on is some fuel economy. Your mechanical advance will give you everything you need as far as timing advance.
    The vacume advance works when there is a lot of vacume in the manifold. such as wheen you are crusing down the freeway. Under vacume it advances the dist all the way to improve gas milage. Under acceleraition the vacume pressure drops and the vacume advance doesn't work at all. Basically the vacume advance was added to distributors as a fuel milage improver. It doesn't affect performance much

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  7. Thunder

    Thunder 3/4 ton status

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    Also the Mallory Unilite's mechanical advance curve is adjustable so you may need to play around with it to get the best performance. There should be instructions how to change the advance and the advance guage( a little black plastic rod with notches on it) included with your Dist.

    <a target="_blank" href=http://coloradok5.com/gallery/Thunders-Blaze>http://coloradok5.com/gallery/Thunders-Blaze</a>
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  8. dyeager535

    dyeager535 1 ton status Premium Member

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    As well, if its hooked up to a Q-jet in the correct advance port, it will only get vacuum at a certain throttle opening. None at idle, and little to none at WOT since there is so little vacuum.


    Dorian
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  9. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Unfortunatly, I have a Holley... and the only vaccuum port on the DAMN thing goes to the trans modulator on my TH400 trans. Sounds like I may need to be selling the intake, carb, and now the distributor as well to setup this truck correctly.[​IMG]

    <font color=red>Just give me a tank, and point me in the right direction!</font color=red>
    <font color=blue>DONT MESS WITH AMERICA!</font color=blue>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
     
  10. HarryH3

    HarryH3 1 ton status Author

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    Just stick a tee in the vacuum line. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  11. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    I have a T in the line already for the vaccuum actuated heater controls...

    But that damn Holley seems to be the root of many evils in my truck! Anyone need a newly rebuilt 750cfm Holley for their drag car???

    <font color=red>Just give me a tank, and point me in the right direction!</font color=red>
    <font color=blue>DONT MESS WITH AMERICA!</font color=blue>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
     

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