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02-25-2024, 04:37 PM | #1 |
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Secondary Well zenith carb
The secondary well opening in lower carb is not threaded, no brass secondary well installed. Looking into the opening there is a step machined partway down the hole. Were some carbs made this way, no secondary well needed?
The carb looks like a zenith but no markings other than an "H" below the intake flange. |
02-25-2024, 05:25 PM | #2 |
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Re: Secondary Well zenith carb
The early dual venturi carburetors made by both Zenith and Holley did not have a removable brass secondary well and therefore no threads were in the lower half. The main and cap jets are usually in a straight line from front to back and there might be pin boss/s that were used to retain the dual venturi.
Dave |
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02-25-2024, 07:11 PM | #3 |
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Re: Secondary Well zenith carb
Now it makes sense, I wondered about the pin retaining the venturi. It had been updated to the later venturi at some point. I'll keep on keeping on with the rebuild, thanx a bunch.
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02-25-2024, 09:37 PM | #4 |
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Re: Secondary Well zenith carb
Double venturi
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02-25-2024, 09:38 PM | #5 |
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Re: Secondary Well zenith carb
If you look carefully at the position and angle of the 2 main jets in the lower carb body half, you can see the difference between the early dual-venturi carb and the later single-venturi carb. There are probably photos of the two online for you to compare.
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Jim Cannon Former MAFCA Technical Director "Have a Model A day!" Last edited by Jim/GA; 02-27-2024 at 12:00 AM. |
02-26-2024, 02:55 PM | #6 |
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Re: Secondary Well zenith carb
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02-27-2024, 12:00 AM | #7 | |
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Re: Secondary Well zenith carb
Quote:
If you mix the parts up as you propose, you will have a throttle response lag when you accelerate. (I don't remember if the Service Bulletins go into this in detail. It's a carb design thing.)
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Jim Cannon Former MAFCA Technical Director "Have a Model A day!" |
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02-29-2024, 12:32 PM | #8 |
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Re: Secondary Well zenith carb
Thanx for the info, time to order the book with service bulletins. Carbs are not my strong suit. J
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