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Vacuum timing

Discussion in 'The Garage' started by eshorvath, Aug 17, 2004.

  1. eshorvath

    eshorvath 1/2 ton status

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    I keep hearing about timing your engine wiith a vacuum gauge..How is this done, or is it a bunch of back woods BS?

    Found out my trucks metering rod was bent, so causing it to run like [darn], replaced it, but have not taken a test drive.
     
  2. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    I found a sight that explained it well. How to do it and why it is a better method. Unfortunately the info is on my work computer. From what I remember it is pretty simple.

    Basically set the timing where the vacuum is highest. They recommended backing it off a little to ensure no detonation.

    I did this with my truck after rebuilding the motor. I had been driving it with the timing set by a light. Wasn't impressed with the acceleration. So I set the timing with vacuum, and it made a huge difference. That is how I'm doing it from now on.

    Don't forget that once you reset the timing, you'll need to re-adjust the mixture and idle speed.

    When you're done, just make sure that you test drive the truck and listen carefully for any knocking. Also be careful about where you're total timing ends up.
     
    Last edited: Dec 27, 2004
  3. eshorvath

    eshorvath 1/2 ton status

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    Where do you plug he vacuum gauge in? Do you still remove he vacuum advance from the distributer? Do you time it at the standard idle?
    Eddie
    If you find that site, could you send it to me?
    Thanks
     
  4. backyardbuilt

    backyardbuilt 1/2 ton status

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    I would like to know that site too as that is how I set my timing, my drag racer buddies showed me what to do but an explanation of what I am doing would be nice.
     
  5. eshorvath

    eshorvath 1/2 ton status

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    NO KIDDING.
    I replaced the metering rods, found a bent one, how in the hell did it bend /forums/images/graemlins/confused.gif

    Id like to adjust his carb (edelbrock) like it is supposed to be, and replace the pick-up springs, bu it recommends using vacuum, and I have no idea how to adjust those using vacuum, I did hear that this could fix my poswer problem...Anyone else adjust their edelbrocks??
    Eddie
     
  6. semper-k-five

    semper-k-five 1/2 ton status

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  7. eshorvath

    eshorvath 1/2 ton status

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    Thanks for the link, it is just what i was wanting...Just a quesion, when it says to adjust the idle mixture screws at hat point, is it with the idle set low like when you adjust the vacuum timing?
    Eddie
     
  8. semper-k-five

    semper-k-five 1/2 ton status

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    if you read the info for the link, it will advise you to set both the idle screws to the point where the motor is almost stumbling...this is elderbrock talk; the left screw is ur low idle and right is ur fast...turn the left in until the motor begins to tumble and turn it out just a hair to pick up the idle...then do the same for the right screw....you want to start w/ the low idle screw for setting the idle...once your done, both screws should be about the same as far as turn outs for leaning...
     
  9. semper-k-five

    semper-k-five 1/2 ton status

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    and yes, you set the screws in before you begin timing w/ the vacume gauge...sorry for not specifying!! /forums/images/graemlins/thumb.gif
     
  10. eshorvath

    eshorvath 1/2 ton status

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    sorry, but i think im more confused now.. /forums/images/graemlins/confused.gif
     
  11. semper-k-five

    semper-k-five 1/2 ton status

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    i probably missunderstood ur question...do a little rephrase action and we'll see what we come up with!
     
  12. k-5 jimmy fan

    k-5 jimmy fan Registered Member

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  13. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    The sight already listed by semper-k-five is the same one I have.

    I disconnected the distributor vacuum advance.

    The vacuum gage should be connected to a manifold vacuum source. I used the same port the vacuum modulator for the tranny was connected.

    I prefer using RPM to set the idle mixture. I use an automotive multimeter that has a tachometer. I keep everything connected and installed: ie the air cleaner housing, vacuum advance, tranny vac mod, etc. Put the tranny in drive with someone (usually my wife) holding the brake. I start with the screws at about 2 turns out. Then I start turning both screws out a quarter turn at a time, taking an RPM reading after each adjustment. The RPMs should increase. I continue doing this until the RPMs drop. Then start turning the screws back in an eighth of a turn until the highest RPM is achieved.

    That's is how I do it, and the truck seems to run good. Granted I don't have to pass emissions, so I don't know if my method is appropriate for that.
     
  14. eshorvath

    eshorvath 1/2 ton status

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    I set mine today using vacuum, and runs a lot better...Also fixed a few vacuum leaks,and OMG, does she run better...

    Need to do a few minor adjustments ont the carb, and check he plugs again o see if she is running lean...But, wow, i can chirp 3rd gear again
    Eddie
     
  15. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Right on! /forums/images/graemlins/waytogo.gif

    Works good doesn't it.
     

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