Airflow to Cubic Inches

Earlie A said

From Darin Morgan's induction seminars, he uses the equation above^^^^^for the cfm demand at max piston speed, which occurs approx 75 degrees ATDC. For average CFM demand he uses the same equation multiplied by 0.6872.

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That to me would give vary low cfm estimates. A 408 x 6000 x 0.0009785 / 8 = 300 cfm so a 190cc trick flow head x 0.6872 = 205 cfm a J head. The trick flow seems to be the right call for that application might get away with a little less but not a J head, at 100% ve the formula says 241 cfm so a Edelbrock/SM head.