zenith carb baffles to prevent stalls during braking

[BILL WILLIAMSON]

Even with a proven "good" carb, the idle speed has to be nice and SLOW in order to get good response from the idle mixture screw! Also, the GAV has nothing to do with idle circuit. If the GAV changes the idle, then your idle speed is TOO FAST!
The GAV is just an additional, adjustable, high speed jet that can be turned on when the main high speed is too lean for current conditions such as temperature, humidity, altitude, load, etc.
Chief taught me: Engine warm, run at a steady 20 to 25 MPH in second gear & adjust GAV for maximum RPM & smooth running. If that setting runs smoothly from cold start-up on up to warm engine, just leave it alone & don't DIDDLE WITH IT! I can just hear him sayin' "Iffin' you keep screwin' with the GAV, you'll wear out the threads on the brass needle, and wouldn't that be a fine KETTLE OF FISH!" (Whatever that's sposed' to mean???---HELP ME, PURDY!) Bill W.

[James G.]

First is to make sure you are using a reliable and simple guide for the carb restoration! Steve Pargeter has a really solid booklet to follow if you are at all handy with simple tools. Check out all major A suppliers and the ads in MAN magazine
.
Then, as Steve would tell you, check the jets and other adjustment parts to be sure they are of original/correct size for that carb, he gives the dimensions. Next make absolutely certain, as Steve will show you, that all the passages are all clear.

Using all the proper parts, clean passages, making the proper adjustments, etc., per Steve, and your carb will perform as Henry prescribed.

Restoring a carb, "as best as I can" most often will not result in good performance. This is not that difficult! Get the book: Zenith Model A Carburetor Restoration Guidelines, by Steve Pargeter. I have versdions 2, 7, and 7a! I restore for my collection and a few friends as a favor. Get the book and study it a few days, get on the Barn or Ahoogaand or both and ask any questions, then go at it. You may be surprised. Flow testing the jets will be the hardest since you will have to build a test stand, but it is really cheap to do and Steve will show you how. Follow these instructions to the letter, then read again to be sure.

Happy A'ing

[sphanna]

Had same problem on way home from Amana Colonies. 167 miles away from home. Worked perfect on way to, but 20 miles into return trip, it would stall at every stop. Very annoying. Ran fine at driving speeds. Took carb apart when home and found idle jet plugged. Cleaned and no more problem.

[Purdy Swoft]

Originally Posted by BILL WILLIAMSON

Even with a proven "good" carb, the idle speed has to be nice and SLOW in order to get good response from the idle mixture screw! Also, the GAV has nothing to do with idle circuit. If the GAV changes the idle, then your idle speed is TOO FAST!
The GAV is just an additional, adjustable, high speed jet that can be turned on when the main high speed is too lean for current conditions such as temperature, humidity, altitude, load, etc.
Chief taught me: Engine warm, run at a steady 20 to 25 MPH in second gear & adjust GAV for maximum RPM & smooth running. If that setting runs smoothly from cold start-up on up to warm engine, just leave it alone & don't DIDDLE WITH IT! I can just hear him sayin' "Iffin' you keep screwin' with the GAV, you'll wear out the threads on the brass needle, and wouldn't that be a fine KETTLE OF FISH!" (Whatever that's sposed' to mean???---HELP ME, PURDY!) Bill W.

Bill, I'd hope you iffin I could, I spect I oughten to a posted on this thread in the first place . The moon is full, spect i'll jist lay low. Purdy.

[BILL WILLIAMSON]

Brother Purdy,
Yep! when the moon is FULL, jist stay in the house & ponder stuff & that's a good time to pray for folk's protection during this ONE OF A KIND STORM! Bill W.

[Bruce Lancaster]

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One telling point is that when Ford DID put baffles into a Zenith, in the last generation of Model B carburetors, the baffles were arranged to control LATERAL movement...possibly the increased cornering load allowed by better paved roads and higher speeds was allowing slosh to reach the vents, pure speculation there, but the lack of attention to endways control affirms the conclusions of our most knowledgable contributors that braking was not seen as a carburetion issue in cars with everything in order.

[ursus]

I recall opening up a later B-carb and finding a 1/4 inch layer of fine steel wool pressed into the bottom. I first thought that somebody had done this to trap particles of dirt or rust passing into the float bowl because, unlike the A carb, the B lacks a filter screen in the inlet portion. Now I wonder if somebody wasn't trying to compensate for the missing baffle that was probably removed along with the spring.

[Bruce Lancaster]

Worse, I once went to work poking into a B fuel pump upper that was full almost to the top with a fine, almost concrete-like silt. When I at last got to the bottom, I discovered that there WAS no bottom...the floor had been completely eaten away and the block of silt was all there was!
Not my best core...
The steel wool could be almost a primitive form of fuel-cell technology!

[Purdy Swoft]

Speaking of the baffels in the bowl of the later B carbs. The model A Zenith and Holley , as in Zenith one and Zenith two had no baffel and is a totaly different design. The float hinges in a different direction. If the float is set too high it will allow the gas to slosh first foward and then back causeing the engine to stall apon braking. My experience has proven this to me.

[Michael Cooper]

When braking, the carby drops into idle, the fault then comes from the secondary well, so stalling has to come only from problems in this area. In my case the idle jet was way to small!
Its going to take some time to drain this well as the idle jet is so small so float hight or slosh would have very little to do with it (ignoring extrems)
Others above have have basicly said this in a different way.

[Michael Cooper]

Follwing the document www.durableperformance.net the recommended flow for the idle jet was 44-48 ml/mn (I was a lot Less) I can remember coming up 1 metric drill size and a bit of filling with the drill-bit to get the 44ml/mn flow.
"Henry" idles sweetly now on a new motor.(with the old motor it did sometimes stall if not court in time)
Hope that helps

[Michael Cooper]

When I restored the 28pickup I left the motor to till a later date. To get the carby to run sort of right we treaded a thin wire into the compenator jet and and apart from oftern stalling when braking she run well apart from a "Arabs thirst for oil"
New motor, time to reset the jets to correct flow rates.
For the idle jet the suggested flow rate is 44-48ml/mn, there was a bit of enlarging of the jet to get a flow of 44ml/mn. The idle is better than I would have expected taking into account a tight new motor.
note: All the jets needed some sort of attention.

[jkassay]

My solution: hope it works for others. 1930 zenith 1
I rebuilt the carb, made numerous adjustments, almost gave up...
I ordered a set of wire drills to check the jet openings. The idle jet is supposed to be a #75 or .021 thousands. I opened it up to .024, re-
installed and now the car runs perfectly. smooth low idle and no stalling on stops.

[Duffy1]

Proper sized jets will correct this problem as P S testified .I had the same problem and put in proper sized jets . PROBLEM SOLVED.

[mshmodela]

Tossing a great artical by Tom Endy, in this month's "The Restorer" on the Zenith Gav seat and needle valve.. in short the needle stuck in the Gav seat and the seat getting turned not the needle...

[stouchton]

Had the same problem and bumped into an old timer at a show....

He asked "does your GAV affect your idle?" - to which I answered yes.

He told me to turn the idle speed down until the GAV no longer affected the idle and the problem will go away.

I lowered the idle until the GAV no longer affected idle and the problem is gone.

The guy had a beautiful car at the show - 1929 Franklin - I had never heard of one before.

[Purdy Swoft]

The GAV effects the idle in all of mine and they don't stall when I come to a stop. I mostly don't have mine on the idle circuit. The idle circuit is really too slow and has a bad effect on gear shifts. The way that we drive our model A's , we have clash free shifts. There can be other causes but stalling is more about float level than anything else. This comes up often. Read the book , Restoring The Model A and B Carburetors The Rex Reheis Way by Gordon Biggar. This is a very good book and will answer all carburetor questions,believe it or not.