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Thread: Which Edelbrock vacuum port?

  1. #1
    Speedster Member
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    McGaheysville, Virginia, USA.
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    Which Edelbrock vacuum port?

    Re: which Carburetor port does the distributor vacuum line
    connect to?

    I saw a reference to this on another post and would like some clarification: My 58 Hawk has the 289 ci engine, and I changed the original carb over to the 500 cfm Edelbrock some time ago. Per the instructions provided with the Edelbrock, the distributor vacuuum advance line for non-emission controlled engines should be connected to the [u]drivers</u> side ("manifold vacuum port)on the carb, and, for emission-controlled engines, to the [u]passenger </u> side ("timed vacuum port").

    I connected mine to the drivers side port. The car runs ok; lacks some power, but ok. I know I could switch back and forth to see if there is any difference, but I would like to know which is "correct".
    thanks,

    Joe D.

  2. #2
    President Member
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    You can call Edelbrock 1-800 # but they will tell you on the passenger side.

    7G-Q1 49 2R12 10G-F5 56B-D4 56B-F2
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  3. #3
    Speedster Member
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    valrico, fl, USA.
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    If you have trouble overheating at idle when the line is on the passenger side, switch it. The difference is where the vacuum port is located. On the Passenger side - the timed side - the port is located just above the throttle plate. this has the effect of shutting off the advance at idle. On the driver's side, the port is just below the throttle plate. If you are fortunate to have the original carb, I would look to see where the vacuum port is located and start with it there. If you are brave, you could research this on the internet. There are 'experts' on both sides of this. All I know is that the driver's side port matches the port on my Avanti's stock AFB (Carter 3506S). When I connected the line to the passenger side - the timed port - my engine ran much hotter at idle. When I switched back - it rarely gets over 190 with the A/C running here in Fl. neither port will affect operation when not idling as manifold vacuum will be used in either case.

  4. #4
    President Member
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    Try putting a vacuum gauge on both ports with the engine idling. The port with no vacuum at idle is the one that is ported vacuum. Use that port for your vacuum advance as Studebakers don't want any vacuum advance at idle. Bud

  5. #5
    President Member
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    Running full vacuum at idle simply advances timing which means you can get the same result by advancing the static timing by moving the distributor. Doing so, will give you more response throughout the RPM range. Of course, advance only to a point that there is no pinging, surging at cruising speeds or labored crank when hot.

    The nice thing about having a choice of ports is that if you run ported vacuum you can move base timing up without being too far advanced at idle.

    I have pictures of an original Stude AFB showing the position of the vacuum port inside the throttle bore and a picture of the Edelbrock showing the two ports and their respective positions in the throttle bore if anyone carse to see them. Speaking strictly for the carb that was originally on my Avanti the distributor advance port is timed, not exposed to full vacuum at idle. So if you wish to duplicate the factory position the passenger side would be correct.

    As pointed out, once you are driving it doesn't matter which port you choose the function will be the same. In fact, the only place the vacuum advance effects performance is in light throttle acceleration and keeping the timing advanced to the proper levels at cruise.

    If the full vacuum port corrects a problem at idle chances are simply advancing the timing at the distributor and running ported vacuum for the advance will net the same result and improve over-all performance. IMHO.

    ErnieR



    quote:Originally posted by valleyguy

    Re: which Carburetor port does the distributor vacuum line
    connect to?

    I saw a reference to this on another post and would like some clarification: My 58 Hawk has the 289 ci engine, and I changed the original carb over to the 500 cfm Edelbrock some time ago. Per the instructions provided with the Edelbrock, the distributor vacuuum advance line for non-emission controlled engines should be connected to the [u]drivers</u> side ("manifold vacuum port)on the carb, and, for emission-controlled engines, to the [u]passenger </u> side ("timed vacuum port").

    I connected mine to the drivers side port. The car runs ok; lacks some power, but ok. I know I could switch back and forth to see if there is any difference, but I would like to know which is "correct".
    thanks,

    Joe D.


    1988 "Beater" Avanti---R5388 @ Macungie 2006

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