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Thread: Zenith Carb - plugging extra holes

  1. #1
    Join Date
    Apr 2010

    Default Zenith Carb - plugging extra holes

    I'm rebuilding my Zenith carb and a couple sources on the web (including one from our host) recommend sealing an extra port in the base by inserting a piece of o-ring. I followed the instructions but when assemblying the halves, I realized that the holes on my carb don't seem to match the ones in the article - so I appear to have plugged the wrong one. Also, it looks like there might be another extra hole that the gasket only partially covers, so I'm wondering if I should plug that one too.

    So my questions are:
    1. Should I swap the holes our host recommends blocking (leave open the one they block and block the other)? Maybe my carb is a different model?
    2. Should I block the other hole not discussed in RN's article and which the gasket doesn't fully cover?

    Hopefully the attached photos explain this better. Here's a link to the RN article.
    Click image for larger version. 

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    1970 Series IIA
    1964 Series IIA [sold]

  2. #2
    Join Date
    Oct 2011
    Mountains of Western Pennsy.


    Don't go plugging things off if you don't know where they go (some passages are very important). It sounds like a maybe/could be type of fix. If you're not sure what is what, leave it alone. Contact Rovers North Tech folks, if you really want to do this, they may lead you in the right direction.

  3. #3
    Join Date
    Dec 2010


    I plugged a bunch of mine during the emissions hey day........ i still have it but i replaced it with a gas hog rottenchester.
    I'll likely have the same issue as you if/when i get around to dealing with this one.

  4. #4
    Join Date
    Apr 2021
    SF Bay Area


    I've rebuilt a couple carbs in my day. There is disappointingly little to know about it. It comes down to good cleaning, air-tight fit, and properly working linkages. Engine performance can be ruined if a port gets clogged, etc. Remember, the Air/Fuel ratio is adjusted only by a tiny screw. A couple turns in or out and the car idles rough. So, something like a port being fully covered is a weird thing. It's going to throw something off. I wouldn't do it. But, it's not that crazy. Worst case, you have to spend another afternoon field-stripping your carb and redo that again. And you get faster each time and more comfortable with doing it. Not bad. You won't break anything. Just make the engine run rough.

    Another thing to note. I haven't done a bunch of these Zienith ones, but the ones they sell now are Chinese reproductions. So, as such, might differ from the factory ones. Might account for differences in specifics.

    Usually you can plug external plugs pretty confidently, as they often go to other devices like distributor vacuum advance, etc...for vaccuum(not carbeuration). So you'd just be plugging vacuum leaks, if un-used. But internal's anyone's guess.

    Looking at your pic, I'd get a paper hole punch and nib the gasket to clear that hole. Carb gaskets go in dry(as you probably know). They do degrade and get cruddy. I can't imagine a factory design that relies on a "half" overlap of a hole. Or a port being fully molded and cast to pass through, then being blocked by a flimsy gasket. This smells of cheap, I'll fitting gasket set or wrong carb, or aftermarket card differences. Still, not a crazy deal. It's just a cardboard gasket. Cut it to fit. As long as you don't mangle it, you should be fine.

    Good luck. Keep us posted.
    ...d ..__ ......... |... | ..__....p
    └/ | \────┴──┴/ | \─┘≡

    1973 Series 3, 109

  5. #5
    Join Date
    Dec 2010


    i've always had issues working on a carb. i'm good with diesel though. Half the time i'm tempted to just buy a new carb.
    this series 2a I have has a nice carb, zenith looking, not a rochester but after market so maybe not a zenith but it looks nice, works good, and as it has headers and a overdrive is a great drive but engine needs new inserts and now the brakes stick. when i get a shop up i'll be able to put it on the road. it looks like a promising vehicle and for what little i have driven it, i like it better than my series 3, but then the 3 has about 170,000 miles on it! (a lot off road).

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