Yes I think you are looking at the float valves.

The idle air bleeds are little pressed in brass inserts. There are four of them on the top of the throttle body. Three for the idle circuit and one for the aux air enrichment system. They can get dirty.

True!!
I also think the throttle plates were not closing the same each time. With the carbs off, I could see where the plates were closing completely without the throttle bellcrank touching the throttle stop screw.
When I initially took the carb apart I had one bank that was exactly as you mentioned, Mike.
#3 was completely closed whereas 1 and 2 were partially opened. With the idle speed adjustment screwed out I loosened the coupling between #2 and #3 to line up all three throttle valves so to close evenly. (Tested the tightness by pouring some fuel on each plates just to make sure it was holding the liquid)
This way you can also check if the plate contour seals good enough.

(Crude method of checking the float levels with a funnel and tubing) MacGyver style for those who are of my generation. ;)

http://forums.pelicanparts.com/uploa...1396313315.jpg

17 to 18mm from the top edge of the carburetors.

http://forums.pelicanparts.com/uploa...1396313473.jpg

you can remove all the enrichment circuit and plug the ports or leave it in place and screw in the big screw in the last picture rendering it inop. but keeping the stock appearance. i made zeniths work on a 3.0 with new ventures and jets, car ran real well. You can use the $50 weber float level gage but you $0.02 works just as well, float level is critical in these carbs.

DanPez, What are those brass fittings that you used for the float gauges? Where do you get those? Do those screw in or did you thread the plastic tubing into the carb plug threads? That looks like it could be good for me seeing as how there's no way in hell I'm going to pay $50 for a float gauge. I have three Porsches with all the problems in the world. I can't afford a $50 tool to be used only on one car.

+1 on the fittings. That's cool. Where did McGyver find them?

Thank you all for sharing your ideas and experience. I'll be going through this process shortly. Is the bench testing for float level accurate, or does it need to be done under pressure (carbs installed)? I have the same question for testing the accel pump volumes.

dho

Adding pressure will raise the float level. Depending on how high you raise the funnel filled with fuel you can simulate 3-4 psi just due to the weight of the column of liquid pushing down on the float valve.

Float levels need to be checked on a running engine:

• Fuel flow is dynamic, not static. Bench setting will not replicate the dynamic flow due to friction and static alignment of the various components. Dynamic setting allows your components to "settle" into their running alignment positions.
• Fuel supply pressure affects float level; fuel delivered under pressure will require more pressure from the float to close the valve. This extra pressure is developed by the float being more submerged in the fuel which means a higher fuel level than is achieved with a bench setting.

Another comment regarding idle mixture screw setting: The 2 1/2 turns open is ONLY a starting point so you can get your engine running; actually Zeniths need another turn open for a starting point. Any variation in air flow will cause the mixture screws to require adjustment to achieve "Lean Best" idle mixture in a particular cylinder. Variations in idle air flow are from tolerances, air flow dynamics and fits of components in the carbs and from variances in intake air flow through each cylinder. In NO situation will you have all six idle mixture screws adjusted to the same number of turns out...I perform idle mixture and idle air screw adjustments on "new" carburetors quite frequently and never see mixture screws set identically.

Unfortunately you need to get the funnel about 120" above the carbs to create ~3.5 psi at the float.

You could run a line from your fuel delivery line in your engine bay to your bench to get fuel to your carb for bench setting and then crack the drain bolts to allow fuel to flow through the carb. Then gently whack the carb to provide some replication of engine vibration.

I didn't realize the Pelican kit had that diaphragm for the enrichment mixing valve. My kits did not have it. It will work assuming the metal cup/plate that goes between it and the spring is still in one piece. But of the 3 zenith bodies I have that metal piece is broken as shown in the photos.

+1 on being careful that the float gauge is not allowed to protrude too far into the bowl and jam the float. I use a washer or two to space it out from the carb.
I like the simple right angle fittings for the float gauge and I'm anxious to hear where you found them.
http://forums.pelicanparts.com/uploa...1396371991.jpg
http://forums.pelicanparts.com/uploa...1396372003.jpg

The tubing going into the drain of the chambers was a transparent ¼” OD pressed fitted to a union elbow barbed fittings. It was a simple setup just to see their static level. (Supplier is Parker Hannifin)
Having about 1psi pressure gave me a good approximation of the float height. I really didn’t have to do any adjustments at this point. The levels were all even.

I agree with Paul to verify them dynamically. The 3-4psi or whatever fuel pressure the pump shoots out will affect the height. (Inertia of the liquid going into the chamber under pressure will change the height) Levels will increase.

As mentioned it’s a crude method just to verify the float levels and at the same time to check if the acceleration pump circuit works fine.

Float level height is mostly to set fuel height in the emulsion tube well which affects when the main circuit is activated. Higher float levels advances the activation of the main circuit and lower retards it. Since the fuel to the accelerator squirters is mechanically sucked into the pump cavities through the check valve and the check valve closes upon throttle actuation, the fuel volume in the accelerator pump is thereby set independently of fuel level in the float wells.

I wanted to update my findings.
I took the enrichment circuit apart and found the diaphragm, spring and metal cup all in tack. I had the spare diaphragms that weren’t used from the kit so I changed those.

Since I had the valve assembly out and the vacuum ports opened I did some blowing through the inlets, of the removed parts, just to see if there was any obstruction.
It seems that there is something preventing the fuel to flow.
I turned on the fuel pump to pressurize / fill the float chambers and removing the mixture control screw. Using suction I should be able to pull fuel and I’m not.
As per the diagram that was posted item #4 and #12, “Metering jet” “Plunger jet” seems to be the issue.
Would the plunger jet be similar to the (plug) that are used under the accelerator squirters? (Prevents back flow so to keep the passage filled with fuel)
Now I gotta find them. :-)

Item #12 is an air bleed jet that helps emulsify the fuel drawn into the mixing "barnacle" screwed to the side of the carb body. The only time fuel is delivered through this "barnacle" is when the engine RPM is high enough and the solenoid is activated which allows fuel to be drawn into the intake tract below the closed throttle plates...an emission era embellishment to reduce nitrous oxides generated by lean fuel mixtures.

Idling in your driveway will not activate this circuit. When idling the throttle plates will have approximately 0.0025" radial clearance with the throttle bores. The air that passes through this space has fuel drawn into it from the hole that the idle mixture screw meters; there is no fuel delivery from the "barnacle" contraption during idle operation. I recommend changing idle jets to something like 55s, perform the "Lean Best" mixture adjustment and be happy.

Suction applied at the port for the #11 metering screw must be great enough to overcome the "make-up" air drawn through #12 (air bleed) and the little fuel supply jet #4 must be clear of debris to supply fuel for this test; alternately you can take the top cover off the carb and blow into the hole with carb cleaner and look for bubbling from the #4 jet. Also, any fuel gallery blockage must be cleared.

Most recommend ignoring this system and blocking it off which is my recommendation as well; it was an attempt to bridge the time from carburated to CIS engines while complying with emission laws without resorting to the MFI cost burden to sale price.

If you are having issues with idle mixtures then your task is to follow the fuel delivery path from the float bowl to the idle mixture screws. All fuel (except accelerator circuit) passes through the main jet and enters the bottom of the emulsion tube well. From there it has two paths: one is up the well and out the hollow wing of the auxiliary venturi which is the path for the "main" circuit; the second path is from near the bottom of the emulsion tube well, up a fuel gallery where a horizontal gallery intersects it (this is where the idle jet is installed) and then back down the external gallery that feeds the progression holes (behind the big, brass screw/plug) and finally to the mixture screw at the bottom. This inner, vertical passage way is difficult to isolate and blow out due to so many different fuel paths near where the main jet resides.

Thanks for the info and recommendation. Its giving me a good idea on the mechanics / physics behind the Enrichment Circuit.
"2.5 thous?" This would explain why a so little vacuum leak / throttle plate position can effect the overrun condition.

As a note I did open up the carb top on bank 4,6,5 and looked inside the float chamber ... I missed the metering screw #4 at the bottom when I last opened them up. (The orifice was clogged)

With the carb top off I blew into the hole passage going to the jet and saw the bubbling passing through. (After it was cleaned) On the same passage I applied suction and was able to get some fuel up.
Another check I did was with the top back on, the mixture control screw half way in, blocking the compensating air inlet with one finger and inserting a flex tube where the diaphragm assemble port goes and applied suction. I was able to pull some fuel where I wasn't before.

I'll check out 1,2,3 .... I wouldn't be surprised if it the same things.

Through all of this at least I'm finding some issues and getting the carbs up to par.

Thanks again.

Glad to hear you found an issue directly relating to your tuning concerns. I applaud your desire to reestablish operation of the ancillary components as originally configured. As I and others have suggested the system would be bypassed.

Just one more thought: Zeniths seem to attract carburetor fires with dire consequences. Typically the "barnacle" on the side of the carbs has burnt components inside. I was thinking on these two topics today and opined that if there is enough heat to create combustion within the barnacle (evidenced by burned gaskets and melted aluminum discs as seen in post #31) then it's operation would be compromised and perhaps in its failure there would also be a mode of failure that would contribute to fires...just a sobering thought. I've seen many of these barnacles with burned components and have seen quite a few melted auxiliary venturis in Zeniths; far higher percentage of issues with Zeniths than Webers which do not use this enrichment system. Leave the barnacle there if you like the looks of it for originality but I again recommend rendering it inoperative.

I checked timing and my Marelli advance, and replaced the cap and rotor with new parts. I readjusted the carbs to 3 turns out, synchronized the non-existent idle (air flow) between the carbs, and then used the synchrometer to turn in each idle adjustment screw until the throat popped showing the pop on the sync. Then I backed each one out 1/4 of a turn. I don't seem to be good at isolating the sound of each cylinder running at idle partly because the carbs won't idle. What do I do after this. If the throats are still popping do I continue to back out the idle adjustment screws?
I'm also not understanding the throttle stop screws. It's the same story. I can adjust them where the engine will run at 1500rpms, idle, and show about 7bar on the meter. When I try to back them off in an attempt to reach 1000rpms and 5bar on the synchrometer, the carbs automatically drop the synchrometer down to 3.5 and the car chugs down and will die if I don't hit the throttles. So when I give it throttle the engine runs up to 2000 and then has to settle back down which takes anywhere from 15 seconds to a minute. If I turn in the throttle stop screws when the car is pulling 3 bars it does nothing until suddenly it will run on 1,500 rpms. I've even tried manually holding the linkage at idle and adjusting the throttle stops to hit the plate, but it also doesn't work. It drops back to 3 bars and the car dies. I'm having trouble finding the difference between idle, and the main circuit.
Last time I somehow got the car to idle pretty well for ten minutes or so until I tried to open the air correctors to match the throats on one carb. When I initially started messing with the carbs all of the air correctors were closed completely. I'm thinking about keeping them closed and just trying to get it to idle.
It's my error that I still haven't checked the float levels, but it doesn't make sense that they would be wrong when I haven't removed the carb or anything on them since starting this.

Another stupid question. Am I supposed to be using the idle adjustment screws, or the air correctors to snyc the throats on each carb? I've read a few explanations for this and they contradict each other.

Hard to say, but the observation about setting 1500rpm easily, but get odd behavior when you try to drop idle is important. It is likely the plates are sticking.

Did you replace all your manifold to head gaskets too? You may have an air leak. I struggled with this for many months. Gasket sealing is a big problem, and it is subtle. New gasket creep can happen, especially the thicker ones. I frequently check the torque on the nuts after the initial runs, and find the nuts turning a little while reapplying torque. You can't wait too long either, because once a leak path opens up it can be hard to impossible to reseal with torquing the nuts.

If you backed out 1/4 turn and you still detect popping, back out another 1/8 turn. You may have gone a little too far. That's the tough part with doing it by ear/feel.

What you can do is very carefully turn the needles back in all the way while counting the number of turns, exactly to the nearest 1/8 turn. Write it down and then go back to 3 turns out, and start again. Did you end up in the same place? I use this trick to train myself to be more observant. If you consistently end up in the same place, that means your ear is getting better! And if you still think 1/4 turn out is not enough, then increase another 1/8 or 1/4 turn.

Plus, if I adjust idle on a warm evening, and then a few days later the morning and day is cold, it can be too lean. I just back out each screw 1/8 turn and drive off. (I'm talking about 65-75F one day and and 25-45F the next type of temperature swing, which is frequent in CT in early spring and late fall)

Process:
The air bleed screw on #1 and #4 should be closed and you adjust the rest. <-- later I will contradict this.

Balance #1 to #4. with throttle stop screws to achieve a common synchronizer flow reading.
Increase air flow, as needed, to #2, #3 to match #1 with air correction screws
Increase air flow, as needed, to #5, #6 to match #4 with air correction screws
Re-balance #1 to #4 with the throttle stop screws to have equal flow reading
Check All
Check Idle RPM & in your case check idle repeatability.

Now, I just said keep #1 and #4 closed, but.... It is not always possible. Sometimes you have to open the air bleeds on #1 and #4 because they are the lowest flowing cylinders. But do this first with all the other air bleed screws closed, Once you set the air bleed screws on #1 and #4 to raise air flow so they are equal to the highest on that side, leave them alone.

So the throttle idle stop move all throttle plates at once.
Air bleed screws add air to only one cylinder, and it adds to the air passing through the throttle plate gap.

After the carbs are air synchronized, then readjust the fuel flow with the idle jet needles to get best lean.

In a nutshell, balance air flow first, then adjust fuel flow to get the right mixture.

This part is where you may find you can't get to 950-1000 rpm idle to stable. If it hunts or is high then low, low then high, then you probably have one of the throttle plates binding and/or an air leak somewhere. I gave up on a 950 rpm idle. I was running 1100rpm idle. for this reason.

It was not happy below that. I end up setting idle mixture at this higher rpm. And frankly, 900-950 is a nice number. 1100 is a nice number too. Modern cars idle close to 600-650. But we have 45+ year old carburetor technology. I am ok with a high idle. I do set it to 900 just to check advance, but the car was not entirely happy being there. Advance is a pure RPM thing, regardless of AFR and such. Once I am done, I increase idle speed.

Now the carbs are getting new bushings and stuff, so this might go away. :)

I assume you are synchronizing air and adjusting fuel flow with the throttle links disconnected.

Then you have to install the drop links to the carbs, adjusting the links so that they open exactly at the same time, and the same amount. This can take some time, especially if the links are old and worn.

I make sure the links are just opening the throttle plates with load on the linkage. I pull on the throttle rod from the transmission to mimic what happens when you drive. I make sure that both throttle plates start to rotate at the same point. I adjust the links and brackets as required to insure this.

A final check is to have someone hold 2000-2500 rpm with the gas pedal, and verify the left and right carbs are still synchronized. If they are not, then the geometry of the brackets are not right to get equal movement left to right. Links should be very close to the same length, and angularity of the links to the carb body, and crossbar need to be very close to insure the throttle open up the same amount. Essentially the left linkage needs to be the mirror image of the right in every way.

You should
1) The links are the same length
2) readjust the cross bar bracket position to get the carbs opening at the same time.
3) readjust the cross bar brackets to insure the relative front-to-rear angle of the link to the carb body is the same on the left and right
4) bend the cross bar arms as need to balance the side-to-side angularity.
5) recheck and adjust until it is perfect, or you are burned out and don't care anymore. ;)