ENGINE MILD HOT WILD
300......N/A..600...650
350......600..650...750
400......650..750...800
450......750..800...850
500......750..850...950
550......850..950...1000
stock vehicle is mild
hotrod is hot
race car is wild
If you're a math dork, the formula is CIxRPM/3456
Or, if you're just lazy, hit this link and follow the directions (up at the top, enter "306":
http://www.holley.com/index.asp?division=Holley