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Vacuum advance Questions for the experts

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Lazydog, Apr 29, 2003.

  1. Lazydog

    Lazydog 1/2 ton status

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    When my truck revs above 2000rpm the power curve seems to go flat, meaning the motor revs but it feels like its not making any power. Can I use a vacuum gauge to test if the vacuum advance diaphram is working properly? What is the max vacuum when it is working(maybe 16Hg). The truck was originally an Auto now converted to Manual, are the distributors different? I was thinking an auto may rev slower so I may need to adjust the timing advance? I thought about using timing tape to see where it is advancing to. Thanks
     
  2. marine_enlisted

    marine_enlisted 1/2 ton status

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    Not sure how much vacuum it takes( I think there are different vacuum advance actuators for different vehicle applications) , but you should start by making sure it holds vacuum. You can either use a vacuum pump or pop the cap and push the arm for the actuator and hold your finger over the end where the hose attaches and it shouldn't move back. Also check to see if your mechanical advance weights move freely and that the springs are in good condition. /forums/images/graemlins/usaflag.gif
     
  3. Lazydog

    Lazydog 1/2 ton status

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    Thanks, I'll look at that first. Does that sound consistent with the performance problems I'm having?
     

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