First A / First Question(s) – Carburetor dilemmas

[CleaningTheGarage]

Purchased my first A (’28 Standard Phaeton) end of May. Through a series of misadventures she didn’t get home until a week ago and I just got her running over the weekend.
She came home with 2 carburetors.
“New” - Rebuilt – But don’t know when, looks really clean, but threads to one of the mounting holes to the manifold is stripped. It had been installed with an over length bolt and a nut ground down on one side to align properly.
“Old” – On the car when purchased, but she was running rough, thus the recommendation to replace which was done before she got home.

I had the privilege yesterday of spending several hours with the gentleman who performed the frame up restoration. It was invaluable in establishing a baseline for the car as far as condition and performance. While there, we swapped the carbs to see if that made a difference in performance. It actually seemed to run a bit better with the old one on, so left it on. When we were done for the day, I trailered her up and towed her the 150 miles to home and let her sit overnight. This morning, she barely started, runs super rough and there is gas spraying from the carb. So apparently, it that carb does have issues

I'’ll switch back to the “New” one, but wonder if running with that funky bolt nut setup is OK, or can it be re-tapped?
To get a known good carb for a spare, would it be better to get a kit for the old one and do it myself, or trade it as a core for a professionally rebuilt one? I think I know the answer to this…
Suggestions on where to get a carb?

[Herb Concord Ca]

Install a Heli-coil. Have done that many times.

[Bob C]

Since the car is new to you I would start with a compression test to get an idea of the general health of the engine. If the compression is good and you have a nice blue spark from the coil then move on to the carb.

[Gene F]

Could throughbolt with a washer and a nylon insert nut.

People tighten carbs down way too tight. sometimes they don't break but end up sucking air from the flange being deformed.

[1crosscut]

Get Les Andrew’s red book and clean / rebuild both carburetors.
Heli coil the one and then you’ll have two good carburetors.

[Thodge]

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You stated in your post that fuel was spraying from the carburetor. Was this an exaggeration and is the fuel just dripping or flowing out of the carb? If so, from where on the carburetor? Is this a stock fuel system? With a gravity feed fuel system, I can’t imagine how fuel would actually spray out unless there were a pretty serious valve problem in the engine.

[Jim/GA]

Add your location. There may be an experienced Model A person near you.

You can rebuild and adjust these carbs. Get the float level right. Make sure the float valve is really sealing as it should.

[700rpm]

You can chase carburetor problems for a long time.The Zenith is more complex than described in the how-to manuals. VOE: I spent much of March and April trying to stop my carb from leaking, applying every book and online suggestion I could find. Nothing worked. I finally gave up and bought a rebuilt Zenith from The Model A Guy on the MAFCA site. Bingo! No leaking in a professional rebuild, and it runs perfectly. Sent my leaker into the rebuillder for a tradein and got a fair trade. Lesson learned: Recognize your limitations. Hire professionals.

[nkaminar]

I am in agreement with having both carburetors professionally rebuilt and doing a compression check. Also in agreement with the idea of a serious valve problem if the carburetor is spraying out fuel and not leaking. It would be helpful to add details about what you observed.

[CleaningTheGarage]

Thanks All!
Regarding the "spraying", with the car idling fuel would drip from the carb. Open the throttle and it sputters/sprays drops out of the air intake. Stock gravity fed system.

I have the red book (and am working my way through the Service Adjustments and PM lists). A compression check and swap back to the other carb on the schedule today.

After digesting the comments, I think start with one that's professionally rebuilt and then try my hand a rebuilding the other. I generally know my limits, but too often find them by going past them.

BTW, just realized these are Tillotson carbs, not Zenith. Back to the forums to kick the Tillotson vs Zenith beehive. Maybe one of both???

[rotorwrench]

I've run a Tillotson for years and they can be made to work well enough. The zinc die cast is soft so the mounting flange nearly always requires filing it down to a flat surface. I put the bushings in the throttle plates to minimize vacuum leakage there. The Marvel Schebler carbs are also respectable units. The Zenith carbs are good carbs but a bit more complex than the soft body replacements.

Model As and engines that set too long can develop crud in the fuel tank and valves can stick if the environment is humid or damp. Modern ethanol laced fuel is hard on them.