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04-15-2018, 01:24 PM | #1 |
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Zenith Carburetor CFM?
My speculation is the Model A needs to breath 100 CFM in stock form. I base this on the engine's volumetric efficiency.
100% Volumetric Efficiency means that the engine can breath its total displacement in one combustion cycle. So for 200 cubic inches, and assuming the "L" head engine has a 50% Volumetric Efficiency, the carburetor needs to be capable of 100 CFM Does anyone know the CFM of the Model A's Zenith carburetor?
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Bob Bidonde |
04-15-2018, 01:43 PM | #2 |
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Re: Zenith Carburetor CFM?
Read all about it in this link from Vince Falter's excellent website:
http://www.fordgarage.com/pages/zenithBcarb.htm |
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04-15-2018, 05:42 PM | #3 |
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Re: Zenith Carburetor CFM?
For a naturally aspirated 4 cycle engine, the cfm consumption may be calculated as follows:
Since 2 revs are required for 1 intake stroke, divide the RPM by 2. Since we are dealing with cubic feet, divide the cubic inch displacement of the engine by 1728 cubic inches in 1 cubic foot. The volumetric efficiency can vary widely. 75% - 85% for more modern engines. Model A engine is probably less than 75%, especially with an air filter. Example: Use 205 cubic inch displacement, since most Model A engines have been bored. Use 2400 RPM. Use 73% vol eff 205/1728 = .1215 ; 2400/2 = 1200 Required CFM = .1215 x 1200 x .73 = 106 cubic feet/min Compare this with Vince Faller's chart.
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Bill Newland |
04-16-2018, 07:07 AM | #4 |
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Re: Zenith Carburetor CFM?
BN, we have similar CFMs, and they are in the range of the Number 20 Venturi used in the Model A per the Zenith Company's chart on Vince's site. So I am calling it a 100 CFM carburetor.
I wonder what performance gain would come from using the Model B's Venturi an jet sizes in the Model A's Zenith?
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Bob Bidonde |
04-16-2018, 09:36 AM | #5 |
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Re: Zenith Carburetor CFM?
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