The Ford Barn

Rex_A_Lott · 10-22-2014, 06:31 AM

Recently there was a thread about running the Stromberg 97's vs 81's so I was digging through an old flathead book I have to look up the CFM ratings of the stock carbs.
I knew they rated two barrels and 4 barrels at a different pressure drop, and the book says that one barrels are rated at 3in H2O like the two barrels.
There was a nice chart there of all the V8 stuff, but nothing on the 4 cylinders.
Anybody happen to know the CFM rating of the stock Model A and the stock Model B carbs ?
I know this really doesnt have much to do with restoration, they are what they are, I was just curious.
I tried a search but I didnt come up with anything. Maybe I did it wrong.

johnbuckley · 10-22-2014, 12:36 PM

Hate to show my ignorance but what is CFM rating? ( Over this side of the pond I only know CFM as cubic feet per minute-if this is what your after presumably you could work it out on displacement and rpm)

Charlie Stephens · 10-22-2014, 12:39 PM

John,

It is cubic feet per minute on this side of the pond. also The question is how many cubic feet per minute will the carburetor flow. There is a set of parameters that need to be met when taking this measurement such as pressure difference across the carb.

Charlie Stephens

ursus · 10-22-2014, 02:51 PM

CFM is a function of the limiting factor, which is the venturi. Vince Falter's excellent Model A Garage website has a section on carbs with a list detailing the CFM for each venturi size available for the A and B carbs. It is interesting that Zenith made a number of venturi sizes, probably for industrial applications. I have a 17mm, 20mm, 22mm, and and 24mm venturis that fit the B-type carburetors. Stock was 20mm for the Model "A" and 22mm for the Model "B".

Rex_A_Lott · 10-22-2014, 05:12 PM

Sponsored Links (Register now to hide all advertisements)

Quote:

Originally Posted by ursus

CFM is a function of the limiting factor, which is the venturi. Vince Falter's excellent Model A Garage website has a section on carbs with a list detailing the CFM for each venturi size available for the A and B carbs. It is interesting that Zenith made a number of venturi sizes, probably for industrial applications. I have a 17mm, 20mm, 22mm, and and 24mm venturis that fit the B-type carburetors. Stock was 20mm for the Model "A" and 22mm for the Model "B".

Thanks! I had read that before but had forgotten about it. And Thanks to Vince for all that info, and the Web page!

10-22-2014, 06:31 AM	#1
Rex_A_Lott Senior Member Join Date: Jun 2011 Location: Upstate South Carolina Posts: 794	Zenith CFM rating Recently there was a thread about running the Stromberg 97's vs 81's so I was digging through an old flathead book I have to look up the CFM ratings of the stock carbs. I knew they rated two barrels and 4 barrels at a different pressure drop, and the book says that one barrels are rated at 3in H2O like the two barrels. There was a nice chart there of all the V8 stuff, but nothing on the 4 cylinders. Anybody happen to know the CFM rating of the stock Model A and the stock Model B carbs ? I know this really doesnt have much to do with restoration, they are what they are, I was just curious. I tried a search but I didnt come up with anything. Maybe I did it wrong.

10-22-2014, 12:36 PM	#2
johnbuckley Senior Member Join Date: Jul 2010 Location: United Kingdom Posts: 1,441	Re: Zenith CFM rating Hate to show my ignorance but what is CFM rating? ( Over this side of the pond I only know CFM as cubic feet per minute-if this is what your after presumably you could work it out on displacement and rpm)

10-22-2014, 12:39 PM	#3
Charlie Stephens Senior Member Join Date: May 2010 Location: Southern California Posts: 7,031	Re: Zenith CFM rating John, It is cubic feet per minute on this side of the pond. also The question is how many cubic feet per minute will the carburetor flow. There is a set of parameters that need to be met when taking this measurement such as pressure difference across the carb. Charlie Stephens

10-22-2014, 02:51 PM	#4
ursus Senior Member Join Date: May 2010 Location: Oregon Posts: 1,375	Re: Zenith CFM rating CFM is a function of the limiting factor, which is the venturi. Vince Falter's excellent Model A Garage website has a section on carbs with a list detailing the CFM for each venturi size available for the A and B carbs. It is interesting that Zenith made a number of venturi sizes, probably for industrial applications. I have a 17mm, 20mm, 22mm, and and 24mm venturis that fit the B-type carburetors. Stock was 20mm for the Model "A" and 22mm for the Model "B".