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rochester vacume port

Discussion in '40- & 55-Series Tech' started by rusmannx, Sep 9, 2003.

  1. rusmannx

    rusmannx

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    ok ok, now i'm still going to try to get this rochester to work before i decide to back to the aisen.

    i need to know where the vacume port is on my 2bbl rochester (i think the nipple has been pulled out and maybe a screw replace... but where?). if any of you have a manual and can look it up and scan a pic for me it would be great. i know there is a haynes manual on rochesters, but i'm sure there are other manuals too.

    my carb ref# is 7012452

    any help would be great. thanks alot
     
  2. OlympiaFJ60

    OlympiaFJ60

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    I am interested in this as well (trying to help a friend get his 40 running). Another question to add, and probably a bonehead rookie one. Does a vacuum advance dist need ported or manifold vacuum?
     
  3. hammerhead

    hammerhead

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    Vacuum advance requires ported vacuum.
     
  4. rusmannx

    rusmannx

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    ok, tell me more about ported vacuum.
     
  5. Gumby

    Gumby Supamod Staff Member s-Moderator

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    manifold vacuum is between the valves and the throttle valve of the carb. It reads high when the throttle is closed and low when the throttle is open. Ported vacuum is between the throttle plate and the top of the carb. It is high when the throttle is open and low at closed throttle.

    I want to say there was two types of distributors. One used just ported and one used both.
     
  6. offcamber40

    offcamber40

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    Ive got a rochester on mine that has no vacuum ports either. I dont know if they ever did. These kits were originally sold by Man-a-fre, and they reccomended you install a non vacuum advance distributor by delco (I recently removed mine becuase it did not deliver proper advance). I put on a non-USA landcruiser distributor with a vacuum advance and ran the vacuum line to the manifold. Hey Gumby, what effect is there on the timing when the distributor line is connected to a manifold port verses one off the carb?
     
  7. Gumby

    Gumby Supamod Staff Member s-Moderator

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    Most pull the advancing mechanism more advanced with the presance of vacuum. That would be the ported type. A manifold vac source to one of these would pull the advance full on at idle and let it retard as the throttle was opened.
    The manifold source on some was to retard the timing under load to prevent spark knock, I beleive. I could be wrong on that one.
     
  8. rusmannx

    rusmannx

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    i don't see any port on my carb. there is however a screw that does absolutly nothing on the front left side (when standing in front of the bumper). i think i'm going to find me a nipple i can thread into this and see what happens.