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Old 08-23-2012, 09:13 AM
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carburator size

Im sure this question has been asked several times over regarding the size of the carb to put on. Thanks to everyone who found the right answers regarding my 350 which turned out to be a 305. So my question is would a edelbrock 600 cfm be to much for the 305. I have a carter c500 carb on it now.

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Old 08-23-2012, 10:13 AM
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If the 500 does not please you then try the 600. Ive used 750s on a 283 with success.
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Old 08-23-2012, 04:48 PM
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I ran an Edelbrock 600cfm Carb on my 1984 305 Pickup for the longest time and it ran great. Go ahead.
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Old 08-23-2012, 08:36 PM
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There is a simple formula to use for a guideline only. Displacement (in cu in) X max RPM X volumetric efficiency (use 92or so if you don't know) all divided by 1728 gives you cfm for a carb. Round up to what's available. Not perfect, but a good starting point for normally aspirated engines.

PatM
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Old 08-23-2012, 09:04 PM
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434 x 6800 =2951200
x .92=2715104
divided by 1728=1571.24?
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Old 08-23-2012, 09:14 PM
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Yes go ahead and try a 600, it'll run great.
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Old 08-24-2012, 12:05 AM
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thanks everyone for your comments ill defenitley try the 600. maybe that will help with my gas mileage. im getting about 8 miles to the gallon so hopefully the old carb may be the problem
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Old 08-24-2012, 12:33 AM
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Quote:
Originally Posted by PatM View Post
There is a simple formula to use for a guideline only. Displacement (in cu in) X max RPM X volumetric efficiency (use 92or so if you don't know) all divided by 1728 gives you cfm for a carb. Round up to what's available. Not perfect, but a good starting point for normally aspirated engines.
You forgot that a cylinder of a four stroke engine only draws in air/fuel every other revolution, so divide your answer by 2.

Bill
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Old 08-24-2012, 12:47 AM
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I would like to see that carb formula applied to a rotary. In 1978 at the old Mission raceway,a mazda r-100 was equipped with a 4781 holley.
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Old 08-24-2012, 06:44 AM
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It depends on the carb adjustments, and the size of the jets and rods.
a 500 cfm it's an old Carter then?
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