Fuel System: Carburetor size questions answered

[colt45sa]

There have been numerous questions posted over time about carburetors and what substitutes are suitable to replace the OEM. Herre is a site that will help you answer the question 'how big?'. http://www.gtsparkplugs.com/CarbCFMCalc.html

[Mike Van Veghten]

There are several of these calculators in/on the net. Most are fairly close. This one seems to be a little on the shy side compared to most.
But yea... These are a good starting point. You also need to reread the first four or so lines in bold letters...the MAIN one being the "Volumetric Efficiency" value.
With many Stude folks falling in the CASO bracket (NOT a put-down !), using over 75%-80% is a dream.

All this says is what many of us have said for years...a 500cfm carburetor (any brand) is more than enough to feed a good running mostly stock 289.
With stock or mostly stock cylinder heads, a stock intake manifold and any flat tappet cam that's currently available...anything more than 500cfm is just short changing much of the overall drivability.
This is one place the Stude engineers got together well. The intake "system" is well matched to all of its pieces.

For what it may be worth, I've had a few carburetors on my 259 powered Lark over the years. I've always gone back to the 500 Edelbrock for the best running combination.

Mike

[bezhawk]

So, I'm right in thinking 1250 cfm for an R4 s a wee bit much?

[DEEPNHOCK]

All at once... Yeah....
But you don't drive with an on/off switch.....(Like a Sopwith Camel)

So, I'm right in thinking 1250 cfm for an R4 s a wee bit much?

[colt45sa]

There are several of these calculators in/on the net. Most are fairly close. This one seems to be a little on the shy side compared to most.
But yea... These are a good starting point. You also need to reread the first four or so lines in bold letters...the MAIN one being the "Volumetric Efficiency" value.
With many Stude folks falling in the CASO bracket (NOT a put-down !), using over 75%-80% is a dream.

All this says is what many of us have said for years...a 500cfm carburetor (any brand) is more than enough to feed a good running mostly stock 289.
With stock or mostly stock cylinder heads, a stock intake manifold and any flat tappet cam that's currently available...anything more than 500cfm is just short changing much of the overall drivability.
This is one place the Stude engineers got together well. The intake "system" is well matched to all of its pieces.

For what it may be worth, I've had a few carburetors on my 259 powered Lark over the years. I've always gone back to the 500 Edelbrock for the best running combination.

Mike

Thanks for pointing out the ''volumetric efficiency" . I took a wild guess when I did the calculation and used 75%. Jeff or one of the others here who are heavily into modification could probably give us a better number for a 'bone stock' 259 or 289.