Quote:
ralliarton18s wrote:
Do you think something in the 500 cfm category is too big with a better flowing exhaust?
If your 1200 engine was worked over to the max, Was capable of 100% volumetric efficiency all the way up to it's unlimited max RPM, it would need to spin at 24,000rpm before it taxed a 500cfm carb. Even with a 250cfm carb, it would need to spin at 12,000rpm to wory it.
The formula that i used is,.. Cubic inch displacement [72 c.i.] X RPM / 3456 = theoretic CFM at 100% VE. This last figure [3456] takes into acount the fact that it takes two revolutions to draw in the rated capacity of the engine.
With a more normal Volumetric Efficiency of say 90%, in a race engine at max rpm, the figures become even more rediculous.
At 100% VE, at a more realistic 6,000rpm, the 1200 [72 cubic inch] engine theoreticly swallows 125 cfm of air. At 8,000rpm, it's 167cfm. Hell, an old Stromberg 97 from a mid 30's Ford V8 flows only slightly less than that.
The two most common sins in modified street engines? Overcaming, & overcarburation.
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