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Holley 94's... can I add vacuum port??

Discussion in 'The Hokey Ass Message Board' started by bob-n, Jul 9, 2007.

  1. bob-n
    Joined: Aug 29, 2006
    Posts: 79


    I've got a pair of Holley 94's on my Dodge flathead 6. Both carbs are casting number 8BA, but neither have the vacuum port for the vacuum advance. I'm wondering if anybody has taken a shot at adding this port? Is it possible or am I going to f-up a pair of good running carbs?
  2. 47bob
    Joined: Oct 28, 2005
    Posts: 625


    Bob, You will need manifold vacuum for that motor;leave the carbs as they are. That 8BA vacuum will give timeing the wrong signel anyway. .....Bob
  3. dickster27
    Joined: Feb 28, 2004
    Posts: 2,917

    from Texas

    Bob, just go to an intake port under the carb and drill and tap a 1/8" pipe thread and screw a nipple in for your vacuum. That's without a doubt the easiest way to get were you want to be. Or, jump on the Bay and win a vacuum plate that mounts beneath the carb. Your call.
    the Dickster
  4. bob-n
    Joined: Aug 29, 2006
    Posts: 79


    I had the advance set up on the manifold, but it didn't "feel" right. Tried running without any vac advance and it ran like shit (like a stock 1 barrel)

    I'll put it back to the manifold then and stop thinking so much.

    Thanks... Bob
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  5. Bob,

    Not the carbs the manifold

    look inside and make sure you drill thru the chamber between the carbs into the common area.

    I did this under the middle carb on my 3 pot and between the two pots on both of my Fentons
  6. Mr 42
    Joined: Mar 27, 2003
    Posts: 1,207

    Mr 42
    from Sweden

    The problem here is when the engine is idling, there should be no vacum to the distributor. Thats the reason for using ported vacum. So you only have the initial vacuum when idling and as soon you open the throttle you will get additonal advance vacuum.

    Henry Fordd tried to save money and made a special distributor advance system. Using the difference between vacum above and under the throttle plate's. And when connecting a Standard 8BA distributor to manifold vacuum it will work backward´s! And when adding more carbs it will need tuning to get it to work right again.

    Check out this article ita a bit old but its still valid.
  7. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,205

    Bruce Lancaster

    This is an engine with "normal" centrifugal/vac advance, probably an Autolite, not the dreaded Holley Loadamatic...
    He didn't like the results with manifold vac, and wants to try ported vac, as I read it...
    With the 8BA carbs, this is simple: You presumably have a plug or a pinched-off original vac line in the '49 Ford advance hole in the rear of the central main body. Remove that...scrutinize the inside area. You have a small hole going straight ahead to the venturi--pluggit any way you like. The second hole, heading down into the throttle body casting, is ported vac. Make sure uou have the proper gasket with a hole for this between main body and throttle casting and try your car with advance hooked up to the '49 Ford setup, venturi vac disabled. This is exactly how Mallory did the job with its aftermarket '49 Ford distributors.
    I believe the passage in carb body may be very small...don't know if this will affect response. You probably own a drill, if it does...
  8. grovedawg
    Joined: Oct 20, 2009
    Posts: 451

    from Heber, UT

  9. Retrorod
    Joined: Jan 25, 2006
    Posts: 1,966


  10. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,205

    Bruce Lancaster

    That way is useful only with the very late carbs that have the extra valve; the common 1949-53 types have ported vac to the rear port for the Loadamatic and need only to have the extra hole for venturi vac plugged, as noted above.
    Look into the hole in the back of the carb...a small hole goes in straight to the venturi. Pluggit. FWIW, early Mallory distributors came with a little plug for just this purpose...
    The remaining downward hole is the ported vac. All you need to to is check on the gasket between throttle and main bodies and make sure you have the right one with a hole for this vac passage.
    If you are using a '37-48 type carb with no vertical vac passage, you can go in right through the base as Ford did on some of the Lincoln V-12 carbs. The Lincolns had a small cast boss for this but you don't really need that.
  11. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,866


    I went to add this thread to the Holley page, but it's already there! I did however add the link to eaton balancing. Thanks grovedawg.
  12. Any pics of this plug or do you know where to get the instructions?

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