Some zenith questions

[Vanspeed]

I took my zenith apart again to drill out the old plugs, clean the passageways and put new plugs in. My kit came with three small plugs and one big. I can only find three plugs. Do you drill out the hole completely? Snyders catalog calls for using an 1/8 inch bit. Last question is about my float. When I took the carb off, I had about 1/4 of gas in the carb. Is this right? I ran it a couple days ago and shut it off before closing the shutoff valve, I never run A's dry. Also, no gas dripped from the line at all. Sorry for the questions but hopefully you can help.

[BILL WILLIAMSON]

Originally Posted by Vanspeed

I took my zenith apart again to drill out the old plugs, clean the passageways and put new plugs in. My kit came with three small plugs and one big. I can only find three plugs. Do you drill out the hole completely? Snyders catalog calls for using an 1/8 inch bit. Last question is about my float. When I took the carb off, I had about 1/4 of gas in the carb. Is this right? I ran it a couple days ago and shut it off before closing the shutoff valve, I never run A's dry. Also, no gas dripped from the line at all. Sorry for the questions but hopefully you can help.

Werner Von Bill here,
My ever so slightly scientific brain says it probably boiled away in the hot carbonator. Old Datsuns with a large glass window in the float chamber would boil the gas about 7 seconds after shut off!
None ever "blew up!" Bill W.

[fordfixer]

That is to low. When you get it put back together, use a sight tube to check the level of fuel in the bowl. You might have to adjust float to get the correct height.

[Mike V. Florida]

Removing and replacing the Plugs.

The ling above talks about "Passage plugs available at most suppliers are dimensioned for Zenith manufactured carburetors. But, some of their sizes will not be correct for many Holly manufactured carburetors."

This may explain the larger plug.

[Vanspeed]

Does anybody know if there is 3 or 4 plugs? I can only find three. My wife suggested that the larger plug might be used in cases where the hole is too big for the smaller plugs. I thought the fuel was low so I will check that when putting it back together. Does anybody know the proper setting? I have no books the cover the zenith carbs.

[30cabriolet]

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Depending on the exact carb you have, there are different size plugs. The plugs that come in the kits fit most, but not all the holes. I have had to turn new plugs to fit the holes that match the kit.
The large plug is located just under the front mounting hole. Be super careful drilling it out as you can easily drill right through the keyhole for the idle jet (hope that makes sense). I personally wouldn't drill it out because you can easily get to that passage through the other plug for the idle.
Before doing any drilling I would suggest trying Tom Endy's way of cleaning out the passages with a paper clip.

http://modelabasics.com/Carb/ZenithPassageways.pdf

[modela-carb]

There are 4 plugs...2 in the lower casting on either side and 2 in the upper casting, a small one under the idle air screw and a larger one at the top under the front manifold mounting flange. Use care when drilling the plugs. Start small (7/64) & work up through 9/64. Often the old plug will spin out with the 9/64. If it doesn't & you have to use the 1/8, be sure you're going in straight as it is easy to wind up with a hole that's too large for the new plug.

& I second 30Cabriolet's comments

[lindy williams]

The larger plug goes in the front side of the upper throat . I have 2 carbs on my bench, both are Holleys and both have 4 plugs. One in the upper throat, one near the idle air screw,one just below the choke driver and one on the back at the bottom near the drain plug.

[fordfixer]

The fuel height in the sight gauge should be 9/16 inch down from the bottom edge of the top half of the carb.

[Farrell In Vancouver]

Originally Posted by Vanspeed

I took my zenith apart again to drill out the old plugs, clean the passageways and put new plugs in. My kit came with three small plugs and one big. I can only find three plugs. Do you drill out the hole completely? Snyders catalog calls for using an 1/8 inch bit. Last question is about my float. When I took the carb off, I had about 1/4 of gas in the carb. Is this right? I ran it a couple days ago and shut it off before closing the shutoff valve, I never run A's dry. Also, no gas dripped from the line at all. Sorry for the questions but hopefully you can help.

Van speed check the flow from the rest of the system before you hang the carb back on. You should get a pretty good flow from the tank into a can with the pet cock open. Odd that the bowl should appear 1/4 full?
Different publications give different hieghts for the float but I like to keep it between 5/8" > 1" from the seam of the float to the bottom of the carb top (held up-side down, no gasket) Not as a "set", but as a starting point. Most will run and idle fine but show chararteristics while drive or stopping, so a little test and tune is always in order. Good luck with the carb!

[Vanspeed]

Originally Posted by lindy williams

The larger plug goes in the front side of the upper throat . I have 2 carbs on my bench, both are Holleys and both have 4 plugs. One in the upper throat, one near the idle air screw,one just below the choke driver and one on the back at the bottom near the drain plug.

Is a zenith the same? I have looked this thing over and over but I can only find 3 plugs. It is a zenith 1. I also do not understand what a sight gauge is, I am used to working on v-8 carbs so I am a little new to these.

[gweilbaker]

look here http://www.snydersantiqueauto.com/2812

[peters180a/170b]

I just received one of my Zenith Carburetors back for PASSING GAS in P.A. Seen his ad in Model "A' News.... Very well done and runs super. It's like brand new carb. Very nice to deal with and he'll have his Model "A' Wide bed pickup at Reading A.A.C.A.National meet in May 19 . I'll be there running his carb too. Not cheap but a super job well done.

[Vanspeed]

Got it back together today and it runs the same! This is what I did. Drilled out plugs, cleaned passageways and ran a paper clip through them to make sure. Replaced all the internals with nice originals I had, including original jets. Blew everything out with compressed air. Checked the seat on the float and it was very nice, no leaks. All new gaskets, and put her back together. Still will only start with GAV 2 turns open and the idle screw can be completely unscrewed from the carb while running with no idle difference. Towel is being thrown in.

[JBohannon]

In a post on this thread someone said they never run their A dry. I always close my valve and let it run out of gas to stop it if I am going to sit for awhile. Is this bad or good.

[JBohannon]

I would like to see how good my flow is to the carburetor by testing flow for one minute. Does anyone know what kind of flow I should have in a minute to the carburetor.

[Mitch Bunkin in PA]

Originally Posted by peters180a/170b

I just received one of my Zenith Carburetors back for PASSING GAS in P.A. Seen his ad in Model "A' News.... Very well done and runs super. It's like brand new carb. Very nice to deal with and he'll have his Model "A' Wide bed pickup at Reading A.A.C.A.National meet in May 19 . I'll be there running his carb too. Not cheap but a super job well done.

I, too, have had a fantastic experience dealing with Neal Frank of "Passing Gas Carburetors." The depth of his knowledge is most impressive. He's a real asset to our hobby.

[TinCup]

Originally Posted by Vanspeed

Got it back together today and it runs the same! This is what I did. Drilled out plugs, cleaned passageways and ran a paper clip through them to make sure. Replaced all the internals with nice originals I had, including original jets. Blew everything out with compressed air. Checked the seat on the float and it was very nice, no leaks. All new gaskets, and put her back together. Still will only start with GAV 2 turns open and the idle screw can be completely unscrewed from the carb while running with no idle difference. Towel is being thrown in.

Did you check the jets for their opening size at the tip?

[1931 flamingo]

Vacuum leak?? Ck intake/exh gaskets.
Paul in CT

[30cabriolet]

Originally Posted by Vanspeed

Got it back together today and it runs the same! This is what I did. Drilled out plugs, cleaned passageways and ran a paper clip through them to make sure. Replaced all the internals with nice originals I had, including original jets. Blew everything out with compressed air. Checked the seat on the float and it was very nice, no leaks. All new gaskets, and put her back together. Still will only start with GAV 2 turns open and the idle screw can be completely unscrewed from the carb while running with no idle difference. Towel is being thrown in.

With everything you did, you are still only about half way through a good carb overhaul. Four things that you did not do immediately come to mind:
1. With the carb in two halves blow into the idle jet while covering the idle keyhole. You should be able to close the idle mixture screw and seal off air flow. If not you need to swap screws until you get one that seals.
2. close the GAV valve, remove the compensator jet and blow air into that passage. There should be no airflow if the GAV seat is good. If not replace the GAV or clean and hone the seat until there is no airflow. Also, some carbs have a removable GAV seat that screws out others have the seat cast into them.
3. How loose is the throttle shaft? Any lateral movement will cause an air leak.
4. You need to flow test the jets. Throwing in original jets is great, but without flow testing them you are just rolling the dice; you may or may not get a good one. Same goes with putting in a new rebuild kit; you are just shooting in the dark hoping for the best.

And lastly, have you put on a known good carb to see if the problem really is the carb?